Evaluation of the Gronnd-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Conntry of Central Texas


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Evaluation of the Gronnd-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Conntry of Central Texas
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Texas Water Development Board
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Bluntzer, Robert L.
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Texas Water Development Board
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The evaluation of the ground-water resources of a part of the Hill Country area of central Texas includes all or part of Bandera, Blanco, Comal, Gillespie, Hays, Kendall, Kerr, Medina, and Travis Counties. This report was prepared in response to the Sixty-ninth Texas Legislature's passage of House Bill 2 which stipulated the identification and study of areas within the State that are experiencing or expected to experience within the next 20 years critical ground-water problems. The relatively extensive study area of all or parts of nine counties has a subhumid to semiarid climate that has low to moderate rainfall and high rates of evaporation. The economy of the area is dominated by agribusiness related to the raising of livestock and exotic game animals, tourism, and hunting, and is significantly influenced by the population and economic growth conditions associated with the metropolitan centers at San Antonio, New Braunfels, San Marcos, and Austin. In 1985, about 62 percent of the water supplies in the area were obtained from the Paleozoic and Cretaceous aquifers. The Paleozoic aquifers include the Hickory and Mid-Cambrian aquifers of Cambrian age, the EllenburgerSan Saba aquifer of Cambrian and Ordovician age, and the Marble Falls aquifer of Pennsylvanian age. The aquifers of Cretaceous age include the Lower Trinity, Middle Trinity, Upper Trinity, and Edwards Plateau aquifers. The average annual recharge to the Paleozoic and Cretaceous aquifers was estimated to be about 450,000 acre-feet. However, because of the erratic occurrence of ground waters within these aquifers and their inherently low to extremely low coefficients of transmissibility and storage, only about 46,000 acre-feet of ground water has been estimated as the annual sustained yield or these aquifers in the study area. Of the 18,739 acre-feet of ground water used in 1985, approximately 74 percent was used for drinking and household purposes (public and domestic uses). Historical development of ground water in areas of concentrated withdrawals for
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Texas Water Development Board, Vol. 339 (1992).

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Texas Water Development Board Report 339 Evaluation of the Gronnd-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Conntry of Central Texas by Robert L. Bluntzer, Geologist August 1992

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Evaluation of Ground-Water Re!IOurces of the Paleowic and Cretaceous Aquifen in the Hill Country of Central Texas Augmtl992 Texas Water Development Board Craig D. Pedersen, Executive Administrator Texas Water Development Board Charles W. Jenness, Chairman William B. Madden Wesley E. Pittman, Vice Chairman Noe Fernandez Luis Chavez Diane E. Umstead Authorization for use or reproduction of any original material contained in this publication, i.e., not obtained from other sources, is freely granted. The Board would appreciate acknowledgement. Published and Distributed by the Texas Water Development Board P.O. Box 13231 Austin, Texas 78711-3231 iii

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The evaluation of the ground-water resources of a part of the Hill Country area of central Texas includes all or part of Bandera, Blanco, Comal, Gillespie, Hays, Kendall, Kerr, Medina, and Travis Counties. This report was prepared in response to the Sixty-ninth Texas Legislature's passage of House Bill 2 which stipulated the identification and study of areas within the State that are experiencing or expected to experience within the next 20 years critical ground-water problems. The relatively extensive study area of all or parts of nine counties has a subhumid to semiarid climate that has low to moderate rainfall and high rates of evaporation. The economy of the area is dominated by agribusiness related to the raising of livestock and exotic game animals, tourism, and hunting, and is significantly influenced by the population and economic growth conditions associated with the metropolitan centers at San Antonio, New Braunfels, San Marcos, and Austin. In 1985, about 62 percent of the water supplies in the area were obtained from the Paleozoic and Cretaceous aquifers. The Paleozoic aquifers include the Hickory and Mid-Cambrian aquifers of Cambrian age, the Ellenburger San Saba aquifer of Cambrian and Ordovician age, and the Marble Falls aquifer of Pennsylvanian age. The aquifers of Cretaceous age include the Lower Trinity, Middle Trinity, Upper Trinity, and Edwards Plateau aquifers. a\erage annual recharge to the Paleozoic and Cretaceous aquifers was estimated to be about 450,000 acre-feet. However, because of the erratic occurrence of ground waters within these aquifers and their inherently low to extremely low coefficients of and storage, only about 46,000 acre-feet of ground water has been estimated as the annual sustained yield or these aquifers in the study area. Of the 18,739 acre-feet of ground water used in 1985, approximately 74 percent was used for drinking and household purposes (public and domestic uses). Historical development of ground water in areas of concentrated withdrawals for public water supply purposes has caused adverse water-level declines, and in some cases the potential for encroachment of poorer quality water and base flow depletion in nearby effluent streams. Adverse water-level declines associated with centers of concentrated withdrawals for public water supply purposes from the Lower Trinity aquifer has caused increases in pumping lifts and corresponding deueases in well yields and drastic depletion of available drawdown. Such water-level decline in areas of concentrated withdrawal in the Middle Trinity aquifer has caused serious reductions in the aquifer's transmissibility and a corresponding decrease in well yields. As well yields decrease, more wells arc needed to meet increasing demands. Conjuncthe use of ground water and surface water has been and is currently being successfully practiced at Kerrville, Boerne, and johnson City. Other public water systems, particularly at Bandera, Comfort, Fredericksburg, Ingram, Blanco, Woodcreek, and Wimberly, should establish conjunctive use programs or seek and develop the additional but limited ground-water supplies available in remote areas away from current centers ofpumpage. In either case, additional water development to meet the increasing water demands expected for the study area through the year 2010 will be costly. v E\"aluation of Ground-Water Re'IOurces of the Paleo1.oic and Cretaceom Aquifer. in the Hill Country of T Augmt ABSTRACT

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Ev-.aluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifen in the Hill Count!J' of Central Texas August 1992 From 1980 to 1985, population increased at a rate of about five percent per year. Similar population increases are expected to occur from 1985 to the year 2010 at an annual rate of about three percent. These historical and projected population increases readily demonstrate that the study area will need additional water supplies for drinking and household purposes (public and domestic uses). From 1985 to 2010, water use for such purposes is expected to increase from about 22,872 acre-feet per year to about 4 7,380 acre-feet per year, a four percent increase per year. Unusually high to excessive concentrations of nitrate have been detected in the ground waters produced from the shallow portions of the Paleozoic and Cretaceous aquifers. The aquifers most effected by this nitrate pollution include the Edwards Plateau, Upper Trinity, Middle Trinity, Marble Falls, Ellenburger-San Saba, and Hickory aquifers. Except for the Edwards Plateau aquifer, such nitrate pollution seems to be limited to scattered local areas, and is believed to be associated with improper disposal of human and/ or animal wastes. The nitrate pollution of the Edwards Plateau aquifer was detected in relatively widespread areas of western Gillespie and northwestern Bandera Counties, and is believed to be associated with nonpoint source pollution from livestock and wildlife excrements. Such nitrate pollution of the Edwards Plateau aquifer was detected to be increasing, and poses a threat to the water quality of the base flow to the upper portions of the Pedemales, Guadalupe, Medina, and Sabinal Rivers in the western part of the study area. Unusually high to excessive concentrations of fluoride and sulfate were detected in the Trinity Group aquifers. Such inherent concentrations of fluoride are found mainly in the deeper portions of the Lower Trinity aquifer. Regional to local occurrences of anhydrite and gypsum beds in the Glen Rose Formation and theCowCreekmemberofthe Travis Peak Formation are the sources of the unusually high to excessive concentrations of sulfate found in ground waters produced from the Upper and Middle Trinity aquifers. In most cases, these inherent concentrations of sulfate can be avoided by proper well construction; particularly by the setting and proper cementing of sufficient casing through the upper unit of the Glen Rose Formation. vi

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TABLE OF CONTENTS Evaluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas Augustl992 Page ABSTRACT ............................................................................................................................ v INTRODUCI'ION ................................................................................................................ 1 Purpose .............................................................................................................................. 1 wcation and I:Xtent . . . . . . . . . . . .. . . . . . . . . . . .. . . . . .. . . . . .. . . . . ... .. . . .. . . . .. . . . . . . . . . . ...... .. . . . . .. . . . . . . . . . . .. . . . . . . . . . . .. . . . 1 Geographic Setting . . . .. .. . .. . . .. . . . . . . . . .. . ... . . . . . . . . . . . .. . . . . . . .. . . . . . . . .. . . . . .. . . . . . . . . .. . . . . .. .. .. . . . . . . . .. . .. .. . . . . . .. . . . 1 Economy and U11d Use ..................................................................................................... 3 Vegetation .. .. . . . . . .. . . . . . .. . . . . . .. . . . . . . .. . . . . .. . . .. . . . . . . . . . .. . . . . .. .. . . . . . . .. .. . .. . . . . .. . . .. . . . . . . . . . . . . . . . .. . . . . . .. . . .. . . . . . .. . . 4 Climate .............................................................................................................................. 4 PreviollS Inves;tigations .. . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . .. . . .. .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. . . . . . . . . .. . . . . . . . . . . 7 Acknowledgentents . . . . . . . . . . . .. . . . . .. . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 8 GROUND-WATER RESOURCES ....................................................................................... 9 Geological Setting . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . .. 9 Stratigraphy . . . .. . . .. . . . .. . . .. . . . .. . .. . .. .. .. .. . . .. .. .. .. .. . . . . .. . . .. .. . .. . .. . . .. . . . .. . .. . .. . .. .. .. .. . .. . . .. . . . .. . .. . . .. . .. . .. .. . .. . .. 9 Structure...... . . .. . .. . .. . . . .. . . . . .. . .. . .. . .. . .. . .. .. . . . .. .. . .. . . . . . .. .. . .. . .. . . .. .. . . .. . . . . .. .. .. .. . .. .. . .. . . . . . . . .. . . . . .. . .. . . . . .. . .. . . 9 Delineation and Relationship of Aquifers . .. .. .. .. .. .. . .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. 25 Hydrological Continuity of Aquifers . .. .. .. .. .. .. . .. .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. . .. . .. . .. .. .. .. . .. .. 26 Recharge, Movement, and of Ground Water .. .. .. . .. .. ... . .. .. .. .. .. .. .. .. .. . .... .. .... .. .. 27 Aquifer Hydraulic Characteristics .. . .. . .. . . .... . .. .. . .. .. .. .. ...... . ...... .. .. . .. .. .. .... . .. .. .. .. .. . . .. .. .. .. .. . .. . 35 Productivity c•fWells ......................................................................................................... 35 Construction of Wells .. . . ... . . . . .. . . . . ... . . . .. . . . . .. . . . ... . . . . .. . . . ... .... .. . . . ... . . . . ... . . ... . . . . .. . . . . . . . . . . .. .. .... . . . . . . 44 Water-Level ........................................................................................................ 48 CHEMICAL QlJALITY OF GROUND WATER ................................................................. 71 GROUND-WA1'ER AVAilABILITY .................................................................................... 89 Utilization and Development of Ground Water .. .. .. . .. .. .. . .. ... .. .. .. . .. .. .. .. .... .. .. .. .. .. .. .. .... .. .. . 89 Estimated Gr'Ound Water Available for Future Development ........................................ 92 Artificial Recharge of Ground .. .. .. . .. .. . .. .. .. .. .. ...... .. .. . .. . .. .. .... .. .. .. . .. ... . .. .. .. . .. .. .. .... .. .. 97 HISTORICAL AND PROJECTED POPULATION, HISTORICAL WATER USE AND PROJECTED WATER DEMANDS ............................................................................. 101 HISTORICAL AND PROJECTED POPULATION ........................................................... 101 Historical Water Use ......................................................................................................... 102 Projected Wa.ter Demands .. .. . .. . . . .. . .. . .. . . . . .. .. . .. .. . .. . .. .. . ... .. .. .. . . . . .. .. .. . . . .. . .. . . . . .. . .. . .. . .. .. . . . . . . . . . . . . 111 EXPECTED WATER DEVELOPMENT AND GROUND-WATER QUALITI PR.OBLEMS .. . . . .. . . . . . .. . . . .. ... . . . . .. . . .... ............... .... . . . . . . .. . . . . .. .. .... . . . . .. .. . . .. . . . . .. . . . . .. . . . . . 113 SUMMARY, C•DNCLUSIONS AND RECOMMENDATIONS .......................................... 117 SELECTED CES .. . . . .. . . .. .. .. .. .. .. . . . .. . .. .. .. .. . .. . .. . .. .. . . . . . . .. .. . . . . .. .. . ... . . .. .. .. . . .. . . . . .. . .. . .. . . . .. . . 119 vii

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Evaluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas August 1992 TABLE oF CoNTENTS (cont'd.) Page TABLES 1. Geological and Hydrological Units and Their Water-Bearing Properties.............................. 11 2. Distribution of Spring Flows by Aquifer ................................................................................... 32 3. Flow ofPro1ninent Springs......................................................................................................... 33 4. Approximate Range in Representative Hydraulic Characteristics of the Paleozoic and Cretaceous Aquifers........................................................................................... 37 5. Approximate Distribution of Well Yields by Aquifer ............................................................... 39 6. Approximate Distribution of Specific Capacities from Wells without Duration of Pumping Time Considered................................................................................... 43 7. Approxima:e Distribution of Specific Capacities from Wells Pumping Two Hours or More.................................................................................................................... 43 8. Approximate Long-Term Net Water--Level Declines in the Hickory and Ellen burger-San Saba Aquifers .. .. . .. . .. . . . . ... ... ... ... . .. ... ... .. . ... .. ... . . . . . . . ... .. . .. . . . . .. . .. . .. . .. . .. . . . . . . . .. . .. . . . . . . . 51 9. Summary of Approximate Net Water-Level Changes in the Trinity Group Aquifers, 1977-1987 ........................................................................................... 52 10. Approximate Distribution of Net Water-Level Changes in the Trinity Group Aquifers, 1977-1987 ........................................................................................... 52 11. Approximate Long-Term Net Water-Level Changes in the Trinity Group Aquifers ....... ....... .................................................... ........................ ... .................. 53 12. Summary of Percent Distributions of Nitrate Concentrations by Aquifer............................. 81 13. Approximate Ground-Water Pumpage in Acre-Feet and Number of Large-Capacity Wells Used in 1985 ........................................................................................... 91 14. Approximate Annual Sustained Yields in Acre-Feet Per Year for the Paleozoic and Cretaceous Aquifers ...................................................................... 96 15. Historical Population in 1980 and 1985 and Projected Population in the Years 1990, 2000, and 2010 ......................................................................... 103 16. Approximate Water Used in 1980 and 1985 ............................................................................ 105 17. Approxima.te Water Used in 1980 and 1985 by Selected Major Public Water Syst.etns....................................................................................................... 106 18. Projected 'Vater Demands in the Years 1990, 2000, and 2010 ................................................ 108 19. 'rV'ater Demands in the Years 1990, 2000, and 2010 for the Selected Major Public Water Systems. ...................................................................................... 108 FIGURES 1. Location of Hill Country Study Are :a ................................................................................... . 2. Average Annual Precipitation and Average Monthly Precipitation for Periods of Record at Selected Stations ............................................................................... .. 3. Geologic ........................................................................................................................ . 4. Approximate Delineation of the Paleozoic and Precambrian Geologic and Hydrologk Units that Outcrop and Subcrop (Underlie) Cretaceous Rocks .................. .. (Explanation Inclucledon Separate Page) ......................................................................... . 5 Geologic Section A-A' ............................................................................................................ . 6. Geologic Section B-B' ............................................................................................................ . 7. Structural Trends .................................................................................................................. . 8. North-South Diagrammatic Cross-Section .......................................................................... . ix 2 5 13 15 17 19 21 23 24

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Evaluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Count'1' of Central Texas Augustl992 TABLE OF CONTENTS (cont'd.) FiGURES (cont'd.) 9. Approximate Directions of Ground-Water Movement, 1987 ........................................... .. 10. Diagrams Showing Basic Types of Well Construction ....................................................... .. 11. Approximate Elevations of the Water Levels of the Lower Trinity, Marble Falls, Ellenburger-San Saba, and Hickory Aquifers in 1987, and Approximate Change in Water Levels from 1977 to 1987 ........................................................................ . 12. Approximate Elevations of the Water Levels of the Middle and Upper Trinity Aquifers and the Edwards Plateau Aquifer in 1987, and Approximate Change in Water Levels from 1977 to 1987 ......................................................................................... .. 13. Hydrographs of Water Levels in Selected Observation Wells, Bandera County, Texas .. .. 14. Hydrographs ofWater Levels in Selected Observation Wells, Blanco County, Texas .... .. 15. Hydrographs ofWater Levels in Selected Observation Wells, Gillespie County, Texas .. . 16. Hydrographs of Water Levels in Selected Observation Wells, Hays and Travis Counties, rexas ..................................................................................................................... . 17. Hydrographs ofWater Levels in Selected Observation Wells, Kendall County, Texas .... . 18. Hydrographs of Water Levels in Selected Observation Wells, Kerr County, Texas ........ .. 19. Sulfate, Chloride, and Dissolved-Solids Content in Water from Selected Wells and Springs ................................................................................................................ .. 20. Distribution of Detected Historical Nitrate Concentrations by Range in Concentration Catagories for the Paleozoic Aquifers in Parts of Blanco and Gillespie c:ounties, Texas .................................................................................................... .. 21. Distribution of Detected Historical Nitrate Concentrations by Range in Concentration Catagories for the Lower Trinity, Upper Trinity and Edwards Plateau Aquifers ............ .. 22. Distribution of Detected Historical Nitrate Concentrations by Range in Concentration Catagories for the Middle Trinity Aquifer .......................................................................... . 23. Large Capacity Well Distribution and Annual Surface-Water and Ground-Water 1955-1986 for Selected Municipalities, Water Districts, and Water Supply Corporations .......................................................................................................................... . APPENDICES Appendix A Table of Chemical Constituent Characteristics ........................................................... .. Appendix B Water Quality Summaries for the Paleozoic and Cretaceous Aquifers ...................... .. Appendix C Distribution of Nitrate, Fluoride and Sulfate Concentrations. Appendix C-1 -Nitrate .................................................................................................................... . Appendix C-2 -Fluoride ................................................................................................................. . Appendix C-3 Sulfate .................................................................................................................... . Appendix D Estimated 1985 Ground-Water Pumpage .................................................................... .. Appendix E Estimated \Vater Use in 1980 and 1985 by County ....................................................... . Appendix F Projected Water Demands for 1990, 2000, and 2010 by County ................................ .. xi Page 29 46 55 57 59 61 63 65 67 69 73 75 77 79 93 A-A15 B-B3 C1-1-C1-9 C2-1-C2-9 C3-1C3-10 D09 E-E5 F-F3

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In 1985, the Sixty-ninth Texas Legislature recognized that certain areas of the State were experiencing or were expected to experience, within the next 20 years, critical ground-water problems. House Bill 2 was enacted which directed the Texas Department of Water Resources to identifY the critical ground-water areas, conduct studies in those areas, and submit its findings and recommendations on whether a ground-water conservation district should be established in the respective areas to address the ground-water problems (Subchapter C, Chapter 52, Texas Water Code). This study of the Hill Country area was conducted to address and evaluate the ground-water problems related to adverse water-level declines and quality deterioration with respect to the Paleozoic and Cretaceous aquifers in all or part of nine counties in central Texas. Discussions of the characteristics and relationships of these aquifers and their relationships to the surface-wat('r regime, a perspective on the amounts of ground water available on a perennial basis and on a sustained basis, and the expected water requirements of the area to the year 2010 are included. The Hill Country study area is located as delineated on Figure 1, and is composed of all of Gillespie, Blanco, Kerr, Bandera, and Kendall Counti('s and parts ofTravis, Hays, Comal, and Medina Counties. The area includes the southeastern portion of the Edwards Plateau in Gillespie, Kerr, Kendall, and Bandera Counties; extends eastward to the Colorado River in Tra\is County and southward and southeastward to the northeastern edge of the Balcones fault zone in Travis, Hays, Co mal, and Medina Counties. The area consist of 5,539 square miles within portions of the Colorado, Guadalupe, San Antonio, and Nueces River basins. The land surface is characterized by a rough and rolling terrain. The nearly flat-lying, erosion-resistive carbonate rocks ofthe Edwards Formation which form the surface of the Edwards Plateau in the western portion of the study area have been deeply incised into the less resistive, marly carbonate rocks of the Glen Rose Formation. The terrain within the Nueces River basin in southwestern Bandera and northern Medina Counties is comprised of highly dissected divides and incised stream valleys. Most of the terrain within the San Antonio, Guadalupe and Colorado River basins is comprised mainly of broad valleys and narrow divides (Ashworth, 1983). Elevations generally range from about 2,300 feet above mean sea level in western Kerr and northwestern Bandera Counties to about 700 to 800 feet above mean sea level to the east in Hays and Travis Counties. of the Ground-Water Resources of the Palemoic and Cretaceous Aquifers in the Hill Country of C-entral Texas July 1992 INTRODUCTION Purpose Location and Extent Geographic Setting

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Evaluation of the Ground-Water Resoun es of the Paleozoic and Cretaceous Aquifers in the! Hill Country of Central Texas July 1992 KERR COUNTY BANDERA COUNTY Figure 1 GILLESPIE COUNTY KENDALL COUNTY BLANCO COUNTY LCCt\TION OF HILL COUNTRY STUDY AREA

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Drainage in the Nueces River basin is generally to the south in the Sabinal River and Seco, Hondo, and Verde Creeks in Bandera and Medina Counties. Drainage in the San Antonio River basin is to the southeast in the Medina River in Bandera County and to the east and southeast in Cibolo Creek in Kendall and Comal Counties. The Guadalupe River and Blanco Riverwhich generally flow ea5.tward are the major streams draining the Guadalupe River basin. The Colorado River basin portion of the study area is drained mainly by the Pedernales River which generally flows eastward in Gillespie and Blanco Counties and into the Colorado River at Lake Travis in western Travis County. Parts ofTravis and Hays Counties are drained by Barton and Onion Creeks which are within the Colorado River basin. The Pedernales, Blanco, Guadalupe, and Medina Rivers are dominantly effluent streams which receive large amounts of base flow from ground water naturally discharged from the Paleozoic and Cretaceous aquifers. The tributaries of these major streams are characterized by two dominant types; namely, the perennial spring-fed streams and theintermittentstreams that only transport storm runoff. A very significant amount of the flows in the Sabinal and !vfedina Rivers and Seco, Hondo, Verde, and Cibolo Creeks are diverted underground as they cross the Balcones fault zone immediately adjacent to the southern portion of the study area. Those flows which are so diverted become recharge to the Edwards (Balcones Fault Zone) aquifer and are naturally discharged from the aquifer as base flow to the Guadalupe River, mainly at Comal Springs at New Braunfels in Comal County outside the studr area and at San Marcos (Aquarena) Springs at San Marcos in Hays County outside the study area. The economy of the Hill Country area is based primarily on the raising of domestic livestock and exotic game animals. Also, the economy is influenced hy a significant, commuting labor force which is employed outside the study area in and ncar San Antonio, New Braunfels, San Marcos, and Austin. Significant income is generated from hunting, tourism, private camps, and resorts. Bccaus:? of its ruggedness and scenic beauty, the area also has and will continue to have a very significant retirement population that directly supports the economy. Some incomes are derived from the cutting of cedar for fence posts and from the quarring of building stone. Most of the rural land in the Hill Country area is used for the raising of domestic livestock and exotic game animals. These rural lands arc extensively used to support the hunting of wild game and imported exotic game animals. Use of the land for hunting has greatly increased in the last 30 years, and p;obably rivals the raising of domestic livestock for ranching income and paymcn t ofland taxes. On the other hand, the great population growth within the last 30 years has caused urban development of the land. Numerous rural residential subdivisions arc most concentrated in eastern Bandera and northwestern Medina Counties, particularly around Medina Lake; along ar.d adjacent to Interstate Highway 10 in Kendall and Kerr Counties; in Comal County on and adjacent to Canyon Lake; in Hays County near Wimberley and Dripping Springs; and in Travis County along Lake Travis, State Highway 71 West, and U.S. Highway 290 West. Evaluation of the Ground-Water Resource• of the Paleozoic and Cretaceous Aquifers in the Hill Country ofC.cntr.&l Texas July 1992 Economy and Land Use

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E\'"dluation of the Ground-Water Resources of the Pal< ozoic and Cretaceous Aquifers in he Hill Country of Central Texas July 1992 Vegetation Climate 4 Because of the limited supply of ground water, the limited amounts of productive soils, and the rising cost of fuel, there is very little irrigation in the study area, although trickle irrigation systems are gaining popularity for watering orchards and vineyards; particularly in Gillespie County. The most productive soils are found in the floodplain areas of the Pedernales, Blanco, Guadalupe and Medina Rivers and some of their tributaries and on the outcrops of the Hickory sandstone and Hensen sand in Gillespie and Blanco Counties. The detailed descriptions and characterizations of the soils in the study area are provided by Werchan, Lowther and Ramsey ( 197 4) for Travis County, Allison, Dittmar and Hensen ( 1975) for Gillespie County, Dittmar, Deike and Richmond (1977) for Medina County, Hensell, Dittmar and Taylor ( 1977) for Bandera County, Dittemore and Allison ( 1979) for Blanco County, Dittemore and Hensell ( 1981) for Kendall County, Batte ( 1984) for Comal and Hays Counties, and Dittemore and Coburn (1986) for Kerr County. A variety of vegetation inhabits the Hill Country. Prairie grasses and stands of Live and Spanish Oak grow on the karstic surface of the upper plateau. "Cedar" (scrub juniper) and Live Oak are prominent in the marly dissected region. Lining the banks of the creeks and rivers are Cypress trees while the terraces support growths of Live and Post Oak, "Cedar", Elm, Hackberry, Cottonwood, Sycamore, and Willow. Varieties of natural grasses include Little Bluestem, Indian Grass, Sideoats Grama, and Texas Winter Grass. The most common in troduccd grasses include Coastal Bermuda, Plains Love grass, Klein Grass, and King Ranch Bluestem (Cuyler, 1931). A number of studies have shown that grasses utilize one-third to one-half as much water as trees and shrubs. Trees, such as the "Cedar" or Juniper, are especially inefficient water users. Several residents of the Hill Country have indicated that creeks and springs on their property have increased in flow since they converted their land from tree growth to grass. A subhumid to semiarid climate prevails throughout the study area. The average annual precipitation ranges from about 33 inches in the east to about 24 inches in the west. During the drought period from 1950 to 1956, the average annual precipitation was about 22 inches. The distribution of average annual precipitation is provided on Figure 2 along with average monthly precipitation for periods of record at seven selected stations. According to this data, approximately 9.0 million acre-feet of precipitation falls on the study area on an average annual basis. The average monthly temperature for the period 1951 to 1980 ranged from a minimum of33Finjanuaryin the northwest to a maximum of96Finjuly throughout mostofthe study region. The annual mean temperature for the period 1951 to 1980 ranged from 66F in the northwest to 68F in the east. The average annual gross lake-surface evaporation for the period 1950 to 1979 ranged from 69 inches in the northwest to 63 inches in the east, (Larkin and Bomar, 1983). These rates of evaporation are more than twice the average annual precipitation.

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County ground-water investigations have been conducted in the study area by George in Comal County, Holt (1956) in Medina County, DeCook (1960) in Hays County, Reeves and Lee (1962) in Bandera County, Reeves (1967) in Kendall County, Reeves (1969) in Kerr County, Follett (1973) in Blanco County and Brune and Duffin (1983) in Travis County. The ground-water conditions in a portion of Gillespie County within and near the City of Fredericksburg was addressed by Mount (1963). Local ground-water conditions in and adjacent to selected communities have been addressed by Sundstrom, Broadhurst and Dwyer ( 1949) and Broadhurst, Sundstrom and Rowley (1950). A number of local water availability studies for public supply purposes have been made by private consulting firms at the request of municipalities within the study area. Regional studies that addressed the ground-water resources of the study area include Lang (1953), Petitt and George (1956), Winslow and Kister (1956) ,AlexandcT, Myers and Dale 1964), Mount and others (1967), Duffin (1974), Walker (1979), Guyton (1979), and Muller and Price (1979). Ashworth (1983) specifically addressed the Trinity Group aquifers in most of the study area and provided valuable data and information for this study and report. Important regional studies that address the geological conditions within the study area include Hill and Vaughan (1898), Hill (1901), Sellards, Adkins and Plummer ( 1932), Sellards and Baker ( 1934), Imlay ( 1945), Cloud and Barnes (1946), Barnes ( 1948), Lozo and Stricklin (1956), Flawn (1956), Barnes and others (1959), Lozo and others (1959), Flawn and others (1961), Young ( 1962), Fisher and Rodda (1967), Young ( 1967), Stricklin, Smith and Lozo ( 1971), Rose ( 1972) and Barnes and Bell ( 1977). The geologic maps presented in this report were adapted from the Llano, San Antonio, Seguin, and Austin sheets of the GeologicAtlasofTexas (scale 1:250,000) which were published by the Bureau of Economic Geology (1974a, 1974b, 1974c, and 1981). Other important geologic maps of the area include Barnes (1952-1956) and Barnes (1963-1982). The Texas Water Development Board and the author wish to thank the numerous individuals who cooperated in providing information on the aquifers in their area, and to the many property owners who allowed access to their wells to measure water levels and sample for chemical quality. Additionally, special thanks are given to a group of individuals who served on an advisory committee that was formed by the Board and the Texas Water Commission to provide a medium through which those most affected by the conditions of the aquifers in the study area could contribute to the study. Thecommitteeconsistedofasmallnumberofconcemedandknowledgeable citizens who represent water users in the study area. A special thanks to Wanda Cooper and Deborah Schultz for typing the manuscript report and also to Mark Hayes and Steve Gifford from the Computer Graphics Unit for the preparation of the illustrations. Paul McElhaney (Geologist) also helped in the preparation of various illustrations. Evaluation of Ground-Water of the and Cretaceous Aquifers in Hill Country July 1992 Previous Investigations Acknowledgements 7

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The stratigraphic sequence showing the positif}n and relationship of the existing geological units at the surface and in the subsurface of the study area is given in Table 1 which provides the oldest geological unit at the bottom and the youngest geological unit at the top. Table 1 also provides the approximate range in thickness and character of rock (lithology) of each significant geological unit. Those units which occur at the surface are delineated in a generalized manner on the geologic map provided in Figure 3. The approximate delineations of the Paleozoic rocks (both Foreland Facies and Ouachita Facies) and the Precambrian rocks directly underlying the lowest occurring Cretaceous rocks in the study area are provided in Figure 4. Figures 5 and 6 provide side-view perspectives of the positions and relationships of t:he Cretaceous, Paleozoic and Precambrian rocks which occur at the surface and in the subsurface. The contact of the lowest occurring Cretaceous rocks with the underlying rocks is a prominent angular unconfcrmity where steeply dipping, deformed, and truncated Paleozoic and o:der rocks underlie the more gently dipping, relatively undisturbed lower Cretaceous rocks. The Llano uplifo: (Figure 7) is a structural high dome of igneous and metamorphic (metasedimentary) Precambrian rocks which occur at the surface and in the subsurface of the northern portion of the study area (Figures 4, 5, 7, and 8). Within northern Gillespie and northern Blanco Counties, local Precambrian granite highs of the Llano uplift have been identified and encountered as upward protruding "knobs" (monadnocks) which penetrate the Paleozoic Foreland Facies and Cretaceous rocks as shown at points A, B, C and Din Figure 8. '.vhere these protruding "knobs" are present, normally occurring Paleozoic Foreland Facies and Cretaceous geological units may have reduced thicknesses or may be entirely absent. Well data and control in parts of Gillespie and Blanco Counties verify the occurrence of such subsurface upward protruding "knobs" as shown at points A, B, and Din Figure 8. Bear Mountain which is a granite outcrop at Palo Alto Creek and Highway 965 north of Fredericksburg is an example of an upward protruding "knob"which locally penetrates Paleozoic Foreland Facies and Cretaceous rocks in the area. The upward protruding "knob" illustrated at poin 1: C in Figure 8 generally illustrates the geological conditions at Bear Mountair.. The Cretaceous rocks (Table 1) consist of relatively gently dipping beds with some on-lapping of the lower beds onto the structurally high Paleozoic and Precambrian rocks associated with the Llano uplift (Figure 7). The dip of Cretaceous rocks in the northern and western part is generally to the south at about 10 to 15 feet per mile. In the southern downdip areas near the Balcones fault zone (Figure 7), the Cretaceous rocks are dipping to the south at about 100 feet per mile. The regional dip of Cretaceous rocks in the eastern part b to the east and southeast at about 100 feet per mile. bdluation of the Ground-Water Resource• of the Paleozoic and Crctaccou• Aquifcn in the Hill Country of C-entral Tcxa• July 1992 GROUND-WATER RESOURCES Geological Setting Stratigraphy Structure 9

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1-\•aluation of the Ground-Water Re ;ources of the Paleozoic and Cretaceous Aquifers n the I-I ill Country of Central Texas July 1992 10 The Paleozoic Foreland Facies rocks (Table 1) which unconformably underlie the lower Cretaceous rocks and which flank the southern portion of the Llano uplift have significantly greater dips than the Cretaceous rocks. Dips of 400 to 900 feet per mile generally to the south and southeast are common. The steepest dipping beds are usuallypresentwhere the Paleozoic rocks are effected by faulting and underlying, upward protruding Precambrian rocks. The regional strike of these rol:ks generally follows the domal shaped trend of the underlying Precambrian rocks of the Llano uplift. Figures 4, 5, 6, 7, and 8 present perspectives on the structural position and relationship of the various Paleozoic and Precambrian rocks underlying the Cretaceous rocks. One of the most prominent structural features are the thrust faults which placed the generally older Paleozoic and Precambrian (?) Ouachita Facies rocks (Table 1) over the generally younger Paleozoic Foreland Facies rocks in the deeper, down dip, subsurface portion of the study area (Figures 5 and 8). The San Marcos arch (A in Figure 7 and lower portion of Figure 6) is a broad, southeast plunging anticlinal structure which is believed to be a subsurface extension of the Llano uplift to the northwest. The Cretaceous geological unit'i overlying this anticlinal structure occur at higher elevations, and the various members of the Travis Peak Formation (Table 1) are significantly thinner on the northeastern flank of the arch in Hays and Travis Counties (Figure 6). Point D in Figure 8 generally illustrates the subsurface geological conditions associated with the San Marcos arch. The Fredericksburg high (B in Figure 7) is a narrow subsurface ridge consisting of structurally high Precambrian and Paleozoic Foreland Facies rocks. It trends southwestward beneath Cretaceous rocks across the study area from the Llano uplift in northeastern Gillespie County to east-central Bandera County where it probably extends beneath the rocks of the Ouachita structural belt. This ridge-like pre-Cretaceous structure may be a narrow extension ofthe Llano uplift formed during late Paleozoic uplift and faulting. The northern portion of this structural high is represented by the undiflerentiated Precambrian rocks directly underlying the Cretaceous rocks as shown on Figure 4 in the area trending southwestward from the Precambrian outcrop just west of Eckert in northeast Gillespie County to Fredericksburg in south central Gillespie County. Points A and Bon Figure 8 generally illustrate the occurrence of this structural high northeast of Fredericksburg. The Precambrian granite outcrop at Bear Mountain north of Fredericksburg, is an upward protruding Precambrian "knob" (monadnock) that is a surface expression of this structural high (Point C in Figure 8). Geological control provided by several wells southwest of Fredericksburg in Gillespie, Kendall, Kerr and Bandera Counties indicates the apparent location and the extension of the Fredericksburg high to the Ouachita structural belt in Bandera County (Figure 7). This linear structural feature may be associated with the development of the San Marcos arch located to the east in Blanco, Comal, and Hays Counties (Figure 7). During the Late Paleozoic to Early Mesozoic, the Paleozoic and Precambrian rocks were extensively faulted. In most of the study area, these faults are covered by Cretaceous deposits (Figures 5 and 6), and only become apparent through close study of available well data control. These faults are very evident in northeastern Gillespie County and northern Blanco County where the extensively faulted Paleozoic Foreland Facies and Precambrian rocks are exposed at the surface (Figure 4). The geological relationship of these faults is demonstrated on the left-hand portion of Figure 8. The two faults associated with point Bon Figure 8 demonstrate an upthrown block

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BEXAR / EXPLANATION San Mcrcos Arch @ 0 F rederkksburg High I ---------Approximate location of normal fault of the Balcones Fault Zone Approximate location of thrust fault and northern limit of Ouachita Facies rocks )f the Ouachita Structural Belt Figure 7 STRUCTURAL TRENDS Evaluation of the Ground-Water of the Paleozoic and Cretaceous Aquifen in the Hill Country of Central Texas july 1992 10 20 30 Miles I I I Scale 23

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E\'llluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 NORTH I SOUTH I I I __ GI LLE SP I E ___ .,.-i,_,.. __ _ : COUNTY KEN D ALL_----i.,._.....r-l ... ,.._-----BEXAR COUNTY COUNTY 24 1 Llano I Uplift I I I Edwards Plateau PCU Balcones !Fault Zone! (Modified i=-rom Flawn,el al.,1961 and Barnes,et al.,1972) EXPLANATION II Tertiary Rocks Foreland Facies Lower Paleozoic Rocks (Cambrian-Devonian) tiE Upper Cretaceous Rocks m Ouachita Facies Lower Paleozoic K Lower Cretaceous Rocks Rocks{ Combrian?-Mississipian) 1:Frprl Foreland Facies Upper Paleozoic Ouachita Facies Rocks of Unknown Rocks (MississipianPennsylvanian) Age (Lower Paleozoic or Precambrian) loFuPl Ouachita Facies Upper Paleozoic I PCU I Precambrian Rocks Undifferentiated Rocks (MississipianPennsylvanian) " Thrust Fault \Yor Normal Faults Figure 8 NrJRTH-SOUTH DIAGRAMATIC CROSS-SECTION

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(horst), while the two faults associated with pointE on Figure 8 demonstrate a down thrown block (graben). The faulted Paleozoic Foreland Facies and Precambrian rocks beneath the Cretaceous rocks in northern and central Gillespie County are shown in Figure 5. Most of the faults which displace the Paleozoic Foreland Facies rocks are high angle (steeply dipping), northeast-southwest and northwest-southeast striking normal faults which have some apparent strike-slip (lateral) displacement and which have associated, similarly oriented fractures or joints. The displacement by normal faulting ranges from a few feet to more than 2,000 feet. The apparent strike-slip (lateral) displacement of some of these faults in the Llano uplift region has been observed to range from a few feet to several miles. Also shown in Figures 5, 6 and 8 in the subsurface of central Kendall County and the northern portion of Bexar County are the thrust faults and folding associated with the deformed Ouachita Facies Paleozoic and Precambrian (?) rocks. The undifferentiated Precambrian rocks shown on Figure 8 were also greatly and extensively deformed during the Pre cam brian by metamorphism, granitic intrusion, folding, and faulting. The Balcones fault zone (Figures 3, 5, 7, and 8) is a system of normal fault'i which generally strike northeast-southwest and disrupt the gently dipping Cretaceous rocks in Bandera, Medina, Bexar, Coma}, Hays, and Travis Counties. The most significant faults displace the Cretaceous rocks about 200 to 700 feet. The down thrown side of most of the faults is toward the coast (faults 1 and 2 in Figure 8). This type of normal faulting developed a "stairstep" group of fault blocks with downward movement coastward. However, some of the faults have their down thrown side landward (fault 3 in Figure 8), and consequently form a graben (downthrown block 4 in Figure 8) in combination with faults with their down thrown side coastward (fault 2 in Figure 8). Study of well data control within the Balcones fault zone indicates that there are steeply eli pping, transversing normal faul to; and perhaps some faults within some of the major fault blocks. Underground cavities of various sizes and shapes are common in the carbonate (limestone and dolomite) rocks of the Edwards Formation, the Glen Rose Formation, the Ellenburger Group, and the San Saba member of the \\7ilberns :Formation (Table 1). These cavities were formed as ground water moved through fault-; and/or associated bedrock fractures or joints and removed carbonate and associated evaporitic rocks by dissolution. The larger cavities may extend vertically and laterally for great distances. They may be expresstd at the land surface by sinkholes and sinkhole depressions which were formed by collapse when the cavities grew to such a large size as to no longer support their overburden. Sinkholes are found in streambeds flowing over the Glen Rose Formation, and sinkhole depressions are common on the Edwards Formation outcrop of the Edwards Plateau. Sinkholes and sinkhole depressions also are found in association with the outcrop and shallow subsurface occurrence of the Ellenburger Group and the San Saba member of the Wilberns Formation (Table 1 and Figure 4). The Paleozoic aquifers pertinent to understanding the occurrence, availability and dependability of the ground-water resources of the study area are from oldest to youngest the Hickory, the Mid-Cambrian, the Ellenburger-San Saba, and the Marble Falls aquifers (Table 1). The important Cretaceous aquifers include the Lower Trinity, the Middle Trinity, the Upper Trinity, the Edwards Plateau, and the Edwards-Trinity (Plateau) aquifers (Table 1). The very local and minor water-bearing uniL'i Evaluation of the Ground-Water Re!K>urces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Delineation and Relationship of Aquifers 25

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in t 1e Hill Country of Central Texas July 1992 Hydrological Continuity of Aquifers which occur in rocks ofPrecam brian and Cenozoic age as indicated in Table 1 are not pertinent to describing the ground-water resources, consequently they will not be given further consideration in this report. The lateral surface and subsurface extents of each of the Paleozoic aquifers are approximately delineated in Figure 4. The northern portion of this map generally shows the outcrops of the Precambrian and Paleozoic geological units provided in Table 1. The recharge areas for the Hickory, Mid Cambrian, Ellenburger-San Saba, and Marble Falls aquifers occur within these outcrops in northern Gillespie and Blanco Counties and adjacent portions of Mason anci Llano Counties. The approximate subsurface delineations of the Precambrian and Paleozoic geological units and the Paleozoic aquifers which underlie the Cretaceous rocks are shown in Figure 4. Also shown arc the approximate down dip extents of slightly saline water in the Hickory and Ellenburger-San Saba aquifers, and the Ouachita Facies rocks that underlie the Cretaceous rocks in the Ouachita structural belt. The outcrops and general extent of the Cretaceous geological units and aquifers arc shown in Figure 3. The vertical perspectives oft he positions and relationships of the Paleozoic and Cretaceous aquifers are provided in Figures 5 and 6. Hydrological continuity or connection of the Cretaceous and Paleozoic aquifers is very common throughout the Hill Country study area. In the large area where Cretaceous rocks overlie the Paleozoic rocks (Figures 3 and t), the HenscH sand member (Middle Trinity aquifer) and the Hosston sand IIICmhn ( LowerTrinityaquifer) an hydrologically connected to the Hickory, l\1ui-Cunhrian, Ellenburger-San Saba, and l\larblc F.1lls aquifers. Figure 5 illustrates the hydrologic continuity of the I knsdl sand with the Hickory sandstone, v\'elge sandstone and undifferentiated rocks of the Ellenburger C1 oup in Gillespie and Kendall Counties, and the sand with the undifferentiated rocksofthe Ellenburger Croup and Marble Falls Formation in Kendall County. fhroughout most of the area where the upper unit of the Glen Rose Formation (Table 1) overlies the lower unit of the Glen Rose Formation (Table 1), the Upper Trinity aquifer and Middle Trinity aquifer are in hydrological continuity (Figures 5 and 6). These aquifers have been differentiated because they have very different water-quality characteristics. The Upper Trinity aquifer has significant beds of anhydrite and gypsum which cause most of the water to be unusually high in sulfate content and slightly to moderately saline. The Middle Trinity aquifer has very little anhydrite and gypsum, and consequently, much better water quality. Even though the Hammett shale member is considered to be a consistently occurring confining bed throughout the study area (Figures 5 and 6), the I .ower Trinity and Middle Trinity aquifers are also hydrologically connected. Hydrogeologically, the three aquifers of the Trinity Group, namely the Lower, Middle, and Upper should be considered a leaky aquifer system. \\'here the Edwards Formation overlies all or part of the Trinity Group aquifers in the Edwards Plateau portion of the study area, the Edwards Plateau aquifer becomes part of the leaky aquifer system forming the Edwards-Trinity (Plateau) aquifer (Figures 5 and 6).

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As indicated in Table 1, Mississippian and Devonian rocks are known to function as confining beds separating the Ellenburger-San Saba aquifer and Marble Falls aquifer. However, these Mississippian and Devonian rocks occur as thin, 5Cattered, remanent deposits, and where absent the Ellen burger-San Saba aquifer and the Marble Falls aquifer are hydrologically connected. The late Paleozoic faulting and associated fracturing displaced Paleozoic Foreland Facies rocks thousands of feet in parts of the study area (Figures 5 and 8). Under these conditions, Paleozoic aquifers were positioned opposite each other and are considered to be hydrologically connected. An example of this condition is illustrated by the large fault which has greatly displaced the Paleozoic Foreland Facies rocks near and beneath the Pedernales River on Figure 5. In this example, the Welge and Lion Mountain sandstones and the Hickory sandstone have been positioned by faulting opposite :he Ellen burger Group; thus providing an opportunity for hydrological con tin ui ty of the Mid-Cambrian and Hickory aquifers with the Ellenburger-San aquifer. Also, such faulting of Paleozoic Foreland Facies rocks has provided displaced and fractured zones through which ground-water of one aquifer is able to flow under differential head conditions to another aquifer even though they are not positioned opposite each other. On an average annual basis, the study area receives about 9.0 million acrefeet of rain fall. Of this amount only about 450,000 acre-feet per year or 5 percent directly recharges the Paleozoic and Cretaceous aquifers by infiltration of rainfall and seepage of stream runoff in the outcrop areas of the aquifers. The outcropsofthevariousgeological unit'iwhich contain the Paleozoic and Cretaceous aquifers are delineated on Figures 3 and 4. Direct recharge to the Paleozoic aquifers is relatively small because of the limited extent'i oLheir outcrops in northern Gillespie and Blanco Counties (Figure 4). Consequently, the Paleozoic aquifers only receive about 12,300 acre-feet per year ::>r about 2. 7 percent of the estimated total annual direct recharge ( 450,000 acre-feet per year). Of this amount, about 8,600 acre-feet is recharge to the Ellenburger-San Saba aquifer, about 2,800 acre-feet is recharge to the Hickory aquifer, about 600 acre-feet per year is recharge to the Mid-Cambrian aquifer and about 300 acre-feet is recharge to the Marble Falls aquifer. These estimated amounts of natural direct recharge do not include the recharge of the Paleozoic aquifers in the large area where they are overlain by Cretaceous rocks. Where the Paleozoic aquifers underlie the Cretaceous rocks, they are readily recharged by downward movement of ground waters from the overlying Hensell sand member and Hosston sand member of the Travis Peak Formation (Figure 5). Since the outcrops of the Edwards Formation, the Glen Rose Formation, and part of the Travis Peak Formation of the Trinity Group occur in most of the study area (Figure 3), the Cretaceous aquifers receive about 97.3 percent or about 437,700 acre-feet of the total average annual direct recharge in the study area. Of this amount, 124,500 acre-feet is recharge to the EdwardsPlate2.u aquifer, and 313,200acre-feetisrecharge to the Upper and Middle Trinit:1 aquifers. Since the Sligo and Hosston members of the Travis Peak Forma jon do not significantly outcrop in the study area (Figure Evaluation of the Ground-Water Re!!Ourccs of the Paleoloic and Crctaceom in the Hill Country of Central Texas July 1992 Recharge, Movement And Discharge of Ground '\Vater 27

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifen in the Hill Country of Central Texas July 199'.! 28 5), the Lower Trinity aquifer is recharged by downward movement of ground water from the Middle Trinity aquifer. The Upper and Middle Trinity aquifers also are locally recharged by an unknown amount of seepage from Medina Lake (Bandera and Medina Counties), Canyon Lake (Comal County}, and Lake Travis (Travis County) (Figure 4). Ground water in the Paleozoic and Cretaceous aquifers moves slowly under the influence of gravity from areas with relatively high water-level elevations to areas with relatively low water-level elevations, and generally from of recharge to areas of discharge. The direction and rate of ground-water movement in these aquifers under natural conditions are controlled 1) by the hydraulic gradient (water-level dip), 2) by the amounts and distribution of rock permeability, 3) by the dip ofthe rock and its bedding plane, and 4) by faults and fractures. The direction and rate of natural movement is readily changed when the hydraulic gradient is altered by the withdrawals from wells. Adequate amounts of data are not available to determine accurately the direction or rate of movement of the water in the Paleozoic aquifers. However, water in these aquifers probably moves southward and southeastward along the dip of the aquifers. In some areas of Gillespie and Blanco Counties, a significant portion of the recharge probably moves into the Middle Trinity aquifer and discharges into the Pedernales River and its tributaries. Consequently, thegeneraldirectionsofground-watermovement in the Pedernales River Valley of Gillespie and Blanco Counties as shown in Figure 9 probably represent the general directions of ground-water movement in the Paleozoic aquifers under these conditions. This condition is particularly apparent for the Ellenburger-San Saba aquifer in the Pedernales River Valley of eastern Gillespie County and northern Blanco County. In other cases, water moves in to the artesian portions of the Paleozoic aquifers and continues to move slowly downdip to the south and southeast. Rates of ground-water movement of 100 to 400 feet per year can be expected for the Hickory aquifer, and probably as much as 1,000 feet per year or more in honeycombed and cavernous limestones and dolomites of the Ellenburger San Saba aquifer. Ground-water movement in the Lower Trinity aquifer is indicated by Ashworth (1983) in parts of Kerr, Kendall, and Bandera Counties. In this part of the study area, water in the aquifer moves southeastward in Kendall County and southwestward in Kerr and Bandera Counties. The groundwater divide indicated just north and west ofln terstate Highway 10 could be shifted further to the west to coincide with the Fredericksburg high (Figure 7). The general directions of ground-water movement in the Middle Trinity aquifer are indicated on Figure 9. Water in the aquifer on a regional basis generally moves to the south, southeast, and east. However, water movement in the aquifer is clearly indicated toward the Medina River in eastern Bandera County; Cibolo Creek in southern Kendall County; the Guadalupe River in eastern Kerr, central Kendall, and central Comal Counties; the Blanco River in southern Blanco and western Hays Counties; and the Pedernales River in Gillespie and Blanco Counties. The ground-water divides delineated in Figure 9 generally coincide with the topographic divides or basin boundaries of the major streams. The general directions of ground-water movement in the Upper Trinity aquifer probably coincide with the directions of movement shown in Figure 9.

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Ground-water movement in the Edwards Plateau aquifer is indicated for the northwestern and western portions of the study area in Walker ( 1979). Water in the aquifer is moving from areas of high water-level elevations, or areas of recharge, to areas oflowwater-level elevations where ground water is discharged to numerous springs and seeps and by evapotranspiration along the edge of the Edwards Plateau (Figure 7), primarily in western Gillespie County, northern Kendall County, and northwestern Bandera County (Figure 3). Ground water is naturally discharged from the Paleozoic and Cretaceous aquifers by springs, by channel seepage associated with the base flow of effluent streams, by subsurface underflow out of the study area, and by evapotranspiration to the atmosphere. Ground water is artificially discharged from the aquifers by numerous wells which are pumped to supply water needed for public supply, rural domestic, irrigation, and livestock watering purposes. Previous groundwater studies and field investigations have inventoried many of the springs which discharge from the Paleozoic and Cretaceous aquifers. The flows of these springs fluctuate due to variable rainfall. The flow of most of the springs is usually low or may cease during periods of low rainfall, and is usually very high during periods of excessive rainfall. Table 2 provides distribution of flow information for 173 springs which have been inventoried in the study area. Some of the prominent springs which have estimated and measured flows in gallons per minute (gpm) are provided in Table 3. These and the many other springs plus stream-channel seepage from the aquifers contribute to the base flow of t:he effluent streams in the study area. Those streams which have stream flow gages and estimated amounts of base flow are the Pe::lernales River, Blanco River, Guadalupe River, Cibolo Creek, Medina Rjver, Hondo Creek, Seco Creek and Sabinal River (Figure 9). The total average or mean annual base flow estimated from the gaged flows of these streams is about 369,100 acre-feet per year. This amount equates to about 2.00 inches per year or about 6.7 percent of the mean annual rainfall (30.0 inches per year). Thisamountofnean annual apparent base flow is considered to be a liberal estimate and ha:; not been adjusted for human activities; namely, groundwater pumpage, diversions of stream flow, municipal and irrigation return flows, and reter.tion structures which cause retained water to be lost to evapotranspiration. However, this mean annual base flow estimate does provide a very reasonable perspective on the mean annual amounts of ground-water discharged from and recharged to the aquifers. Annual base flow or ground-water discharge can vary considerably depending on the amount, frequency, and distribution of annual rainfall. As an example, in 1956 during an extreme drought, the estimated base flow was only about 18,800 acre-feet which equates to only about 0.07 inches of the 1956 annual rahfall. On the other hand, in 1975 during a very wet period, the base flow was estimated to be about million acre-feet which equates to about 4.57 i:-tcl1es of the 1975 annual rainfall. An interpretation of rainfall and data and information provided by Kuniansky (1989) for a period having above normal rainfall indicates that from December 1974 through March 1977 (28 months) the mean annual base flow was about 1.03 million acre-feet or about 10.8 percent of the annual rainfall. b.tluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 31

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Evaluation o the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 32 Table 2. Oistribution of Reported Spring Flows Diatribution by Flow Catagories in Gallon. Per Minute Number 5 or 6 to 21 to 101 to More Aquifer Inventoried less 20 100 500 than 500 Hickory 5 2 1 1 1 0 Percent 100% 40% 20% 20% 20% 0 Mid-Cambrian 2 1 1 0 0 0 Percent 100% 50% 50% --EllenburgerSan Saba 13 4 3 3 2 I Percent 100% 31% 23% 23% 15% 8% Marble FaHs 0 0 0 0 0 0 Percent ------Total Paleozoic 20 7 5 4 3 1 Percent 100% 35% 25% 20% 15% 5% Lower Trinity 0 0 0 0 0 0 Percent -----Middle Trinity 38 1 7 17 6 7 Percenl 100% 3% 18% 45% 16% 18% Upper Trinity 54 10 24 19 I 0 Percent 100% 19% 44% 35% 2% -Edwards Plateau 61 14 19 19 5 4 Percen1t 100% 23% 31% 31% 8% 7% Total Cretaceous 153 25 50 55 12 11 Percent 100% 16% 33% 36% 8% 7% Total Study Area 173 32 55 59 15 12 Percent 100% 18% 32% 34% 9% 7%

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Table 3. Flow of Prominent Springs Aquifer Hickory Ellenburger San Saba Ellenburger San Saba Ellenburger San Saba Middle Trinity Middle Trinity Middle Trinity Middle Trinity Middle Trinity Middle Trinity Middle Trinity Middle Trinity Plateau Edwards Plateau Edwards Plateau Edwards Plateau Edwards Plateau County Blanco Blanco Blanco Gillespie Coma) Co111al Co mal Coma) Co mal Co mal I lays Kendall Gillespie Gillespie Gillespie Kerr Kerr Spring N arne and Location Buffalo Spring on Buffalo Creek Crofts Spring on Salter Springs Creek Hobbs Spring on Pedernales River Lange Mill Spring into Threadgill Creek Rebecca Creek Spring into Guadalupe River Spring Branch Spring into Guadalupe River Honey Creek Spring into Guadalupe River Big Spring on Guadalupe River (under Canyon Lake) Two unnamed springs on Guadalupe Rivn (under Canyon Lake) Bear Creek Spring into Guadalupe River Jacob's Well Spring on Cypress Creek Harwell Springs ( 4 springs) on Curry Creek Headwater Spring of Pedernales River near Harper Trough Spring; on Trough Spring: Creek Pape Spring on Klein Branch Creek Ellebracht Spring near Mountain Home Fish Hatchery Spring near Mountain Home Estimated* or Measured** Flow gpm Year 500* 1941 60** 1938 1,650** 1968 471** 1969 400* 1984 1,750* 1943 300* 1976 5,000* 1945 1,250* 1944 1,750** 193R 6,300* 19-14 200* 2,250* 1945 1,070* 1955 178** 1940 1,110** 196-1 1,000* 1936 9,000* 1960 2,000* 1961 480** 1970 1,500* 1960 310* 1970 500* 1966 2,500* 1966 h•d)uation of the Ground-Water Re!lource• of the Paleo7.oic and Gretaceom in the Hill Country of Central Texa• July 1992 33

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Evaluation of the Ground-Water Re!K•urces of the Paleozoic and Creta<:eous in the Hill Country of Central Texas July 1992 34 Ashworth (1983) indicates that recharge of the Trinity Group aquifers approximately equates to 4 percent of the mean or average annual rainfall. Using 4 percent as a conservative estimate, the mean annual apparent base flow of 369,100 acre-feet would equate to about 223,700 acre-feet for the gaged area and about349,100acre-feetfor the total Hill Country study area. On the other hand, by using the 2.00 inches per year (6.7 percent of mean annual rainfall) as a liberal consideration, the study area would have a mean annual apparent base flow of 577,200 acre-feet. Therefore, the mean annual ground-water discharge as base flow to area effi uen t streams pro ranges from about 249,100 acre-feet (4 percent of mean annual rainfall) to about 577,200 acre-feet (6.7 percent of mean annual rainfall). For this report, it is reasonable to assume that the mean annual ground-water discharge as base flow to area effluent streams equates to about 432,000 acre-feet per year (5 percent of mean annual rainfall). In addition to ground water discharged as base flow, ground water is discharged as subsurface underflow beneath the eastern, southeastern, and southern boundaries of the study area. Interpretation of data and information provided by Ashworth ( 1983) indicates that this underflow discharge may be about 18,000 acre-feet per year. This amount reasonably correlates with estimates of underflow from the Glen Rose Formation to the Edwards (Balcones Fault Zone) aquifer determined by Lowry (1955). Therefore, the mean annual amount of ground water being discharged from the study area is about 450,000 acre-feet per year with about 432,000 acre-feet per year as base flow to area effluent streams and 18,000 acre-feet per year as subsurface underflow. Without consideration to discharge by evapotranspiration, it is reasonable to assume that this is the total estimated amount of mean annual net recharge received by the main zones of saturation of the Paleozoic and Cretaceous aquifers. Suflicien t data and an accurate methodology are not available to reasonably determine the amount of ground water being discharged by evapotranspiration. However, this type of discharge is likely to be very high, probably hundreds of thousands of acre-feet per year. Ground water is discharged from the Paleozoic and Cretaceous aquifer by numerous wells used for public supply, rural domestic, manufacturing, irrigation, and livestock watering purposes. For these purposes, approximately 17,828 acre-feet was withdrawn by wells in 1980, and approximately 18,739 acre-feet was withdrawn by wells in 1985. Approximately 71 to 74 percent of the water withdrawn by wells has been used for public supply and rural domestic purposes for drinking, lawn watering, gardening, and other household uses. The largest ground-water withdrawals from the Paleozoic aquifers are by the City of Fredericksburg and the City of Johnson City. The City of Fredericksburg withdraws ground water from the Hickory, Ellen burger-San Saba, and Middle Trinity aquifers. The City of Johnson City withdraws ground water from the Ellenburger-San Saba aquifer. Significant amounts of ground water are withdrawn from the Paleozoic aquifers in Gillespie and BlancoCountiesforusebyruralresidentialsubdivisionsandunincorporated communities. The Trinity Group aquifers provide all or part of the water supply for such communi ties as Bandera, Dripping Springs, Boerne, Comfort, and Kerrville. The Trinity Group aquifers also supply significant amounts of ground water to many rural residential subdivisions and unincorporated communities located in Bandera, Kerr, Kendall, Comal, Hays, and Travis Counties.

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The quantity of water that an aquifercontainsand will yield to wells depends on its hydraulic characteristics. These important characteristics include porosity and the coefficients of storage (indudingspecificyield), permeability and transmissibility. Table 4 provides a reasonable perspective of available representative hydraulic characteristics estimated for geological units of the Paleozoic and Cretaceous aquifers in and adjacent to the study area. The laboratory porosity data was obtained from the Texas Water Development Board's laboratory files and are the result o:: core testing for various ground-water investigations. The hydraulic characteristics determined from pumping test were compiled from data and information given in Alexander and others ( 1964), Ashworth (1983), Brune and Duffin (1983), Follett (1973), Guyton (1973), Meyers (1969), Mount (1963), Mount and others (1967), Reeves ( 1967), Reeves (1969), Sieh (1975), and Walker (1979) .. All or most of the characteristics for the Hickory, Ellenburger-San Saba and Edwards (Balcones Fault Zone) aquifers given in Table 4 are from test wells in areas immediately adjacent to the study area. However, they are considered to be representative characteristics which are intended to provide a reasonable perspective of such hydraulic characteristics of the respective aquifers within the study area. Because most of the fresh to slightly saline ground water in carbonate aquifers occurs in solution-formed openings which are not uniform and which may be very erratic in size and distribution, the actual hydraulic characteristics c•f such aquifers are usual:ly extremely variable. Therefore, the hydraulic characteristics determined at any one well orwell field cannot be considered t3 accurately represent such characteristics for the aquifer throughout its extent. Because of this condition of non-uniformity of hydraulic chara::teristics, a quantitative determination of storage and yield of such carbonate, water-bearing geological units such as the Ellenburger Group, San Saba limestone, Sligo limestone, Cow Creek limestone, Glen Rose Formation and Edwards Formation (Table 1) should be used with caution, and only as approximations. As indicated in Table 4, the hydraulic characteristics of the Trinity Group aquifers are inherently deficient, having comparatively small to very small coefficients of and transmissibility. Because of these deficiencies, most Trinity Group aquifer wells experience unusually large drawdowns, serious reduction in well yields, and relatively poor water-level recovery after extended periods of pumping. These conditions are particularly evident within and near centers of concentrated ground-water withdrawals utilized for pub:.ic water supply purposes. The productivity of a well is determined by the measurement of its yield and specific capacity. Yield is the volume of water discharged from a well per unit of time, and is measured as a pumping rate in gallons per minute (gpm). Specific capacity of a well is its yield (gpm) per unit of drawdown in feet (ft), andisexpressedasgallonsperminuteperfoot(gpm/ft)ofdrawdownSpecific Evaluation of the Ground-Water Rc50urces of the Palco7.0ic and Cretaceous Aquifers in the Hill C',ountry ofc'.entr•l Texas July 1992 Aquifer Hydraulic Otaracteristics Productivity of Wells 35

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E\•.1luation of the Ground-Water Rcsourets of the Paleot.oic and Cretaceous Aquifers in the Hill Country of Central Tcxa\ July 1992 36 capacity of a well is most meaningfully measured after a specific duration of pumping time has elapsed. The drawdown and yield are measured simultaneously and the specific capacity is calculated by dividing the yield (gpm) by the drawdown (ft). Specific capacity of a well changes with changes in pumping time and well discharge, and decreases when pumping time, well discharge and drawdown increase (Driscoll, 1986). Within the study area, the yields of wells and springs (see previous section on spring flows) may be described according to the following classification: Range In Yields By Catagories (gpm) 5 or less 6 to 20 21 to 100 101 to 500 More than 500 Classification of Yield Catagories Very Small Small Moderate Large Very Large The well inventories, which were conducted during previous ground-water investigations and during a very limited supplemental investigation for this study, provided the yields of 2,152 wells completed in the Paleozoic and Cretaceous aquifers. Such inventoried yields consist of those measured during various investigations and those estimated and reported by water well drillers, well operators and well owners. Table 5 provides a perspective on the 2,1 yields inventoried by giving the distribution by yield catagories, by aquifer, and by county or groups of counties. Also provided by aquifer is the maximum yield reported, weighted average yield, the percent that. is weighted average or greater, and the percent. that is greater than 20 gpm. A general perspective on the chance or probability of the amount of well yield that may be expected from the Paleozoic and Cretaceous aquifers can be determined approximately by area from the data tabulated in Table 5. The "\Veigh ted Average Yields" calculated and shown for the Paleozoic and Cretaceous aquifers in Table 5 generally indicate the aquifers having the most and least productive wells. The Paleozoic aquifers in order of most to least productivity by weighted average well yield are the Ellenburger-San Saba (65 gpm), Hickory (40 gpm), Marble Falls (35 gpm) and the MidCambrian (20 gpm). The Cretaceous aquifers in order of most to least productivitybyweighted average well yield are the Lower Trinity (230gpm), Middle Trinity (55 gpm), Upper Trinity (25 gpm) and the Edwards Plateau (15 gpm). The well yields used in Table 5 for the Cretaceous aquifers include those well yields determined after acidizing. The following discussions which are provided by aquifer include the probability of well yields that can be expected. Such probability is expressed as a percentage of the total number of well yields that were inventoried for each aquifer historically as indicated in Table 5. Some of the percent probabilities in the following discussions have been rounded to the nearest percent from the percentages given for each aquifer in Table 5. If a yield or yield category has an 80 percent probability, then it should be assumed that 80 out of 100 wells to be completed in the future will have that yield or have a yield that will fall within the specified yield category.

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous in the Hill Country of .cntral Texas July 1992 Table 4. Approximate Range in Representative Hydraulic Characteristics of the Paleozoic and Creta(:eous Aquifers Laboratory Geological Porosity Approximate Results Detennined from Pumping Tests Aquifer Units of Core Coef. of Storage Penneability Transmissibility (%Vol.) (Dimensionless) (gpd/ft2) (gpd/ft) Hickory Hickory Sand3-42 0.0001-0.00004 38-1,038 5,000-44,000 stone Member Ellen burger-San Saba Lime1-8 126,000 San Saba stone Member Ellen burger do Group 1-17 0.0022 550-678 56,000-96,000 Hosston Sand Lower and Sligo 1-29 0.00002-0.00005 5-268 150-25,000 Trinity Limestone Members Cow Creek Middle Limestone 5-38 49 3,300 Trinity Member do Hensell Sand 11-34 0.0000008-0.00005 5-9 600-1,100 Member do Lower Unit9-28 0.000002 47-115 700-9,300 Glen Rose Fm. Upper Upper Unit 3-20 1,500 Trinity Glen Rose Fm. Edwards (Balcones Edwards 3-26 0.0004-0.020 4-877 1 '900-386, 000 Fault Zone) Formation 37

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Emluation of the Ground-Water Reso .trees of the Paleozoic and Cretaceous Aquifers in the Hill C"-ountry of Central Texas July 1992 38 Hickory Aquifer-Approximately 85 percent of the wells to be completed in the Hickory aquifer in Blanco and Gillespie Counties may be expected to have small to moderate yields. Only about 22 percent may be expected to yield 40 gpm or more, while about 41 percent may provide a yield greater than 20 gpm. Wells completed for rural domestic and/ or livestock watering purposes have been reported to yield about 1 to 170 gpm. Historically, Hickory wells used for public supply have yielded about 200 to 790 gpm, while irrigation wells have been reported to produce 25 to 327 gpm. Mid-Cambrian Aquifer -Approximately 50 percent of the wells to be completed in the Mid-Cambrian aquifer in Blanco and Gillespie Counties may be expected to have small yields. Approximately 53 percent may be expected to yield 20 gpm or more, while 32 percent may yield more than 20 gpm. Consequently, 21 percent of the wells may be expected to yield about 20 gpm. Wells completed for rural domestic and/or livestock watering purposes have been reported to yield about 1 to 50 gpm. The largest historical well yield was 60 gpm obtained in a public supply test well in southcentral Gillespie County. Ellenburger-San Saba Aquifer-Approximately 82 percent of the wells to be completed in the Ellenburger-San Saba aquifer in or near the Pedernales River Valley of Blanco and Gillespie Counties may be expected to have small to moderate yie Ids. Approximately 10 percent probably will yield more than 100 gpm, while 19 percent may yield 65 gpm or more, and 55 percent may yield mo:re than 20 gpm. Wells completed for rural domestic and/or livestock watering purposes have been reported to yield about 1 to 500 gpm. Historically, Ellenburger-San Saba wells tested and/ or used for public supply have yielded about 14 to 1,500 gpm, while irrigation wells have been reported to produce about 20 to 610 gpm. Marble Falls Aquifer-Approximately 63 percentofthewells to be completed in the Marble Falls aquifer in parts of eastern Gillespie County and eastern Blanco County may be expected to have very small to small yields. Approximately 25 percent may yield 35 gpm or more, while 37 percent may yield more than 20 gpm. Wells completed for rural domestic and/or livestock watering purposes have been reported to yield about 1 to 100 gpm. Historically, Marble Falls wells have not been used for public supply purposes .. Irrigation wells have been reported to produce about 100 to 200 gpm. Lower Trinity Aquifer -Approximately 60 percent of the wells to be completed in the Lower Trinity aquifer may be expected to have small to moderate yields. About 18 percent may yield 230 gpm or more, while 66 percent may yield more than 20 gpm. The most productive yields can be expected to occur in Bandera and Kerr Counties and portions of western Kendall County, where the weighted average yield was determined to be about 41.5 gpm. Wells completed for rural domestic and/or livestock watering purposes have been reported to yield about 3 to 275 gpm. Historically, Lower Trinity wells used for public supply have yielded about 10 to 1,400 gpm, while irrigation wells have been reported to produce about 25 to 1,100 gpm. Well yields have been significantly increased by acidizing. Middle Trinity Aquifer -Approximately 76 percent of the wells to be completed in the Middle Trinity aquifer may be expected to have small to moderate yields. About 17 percent may yield 55 gpm or more, while 42 percent may yield more than 20 gpm. The most productive yields can be expected to occur in Kerr, Bandera, northern Medina, and western Hays

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Table 5. Approximate Distribution of Well Yields by Aquifer Distribution By Yield Catagories (gpm) By Number (No.) and Percent (%) More Weighted Percent Number 5 or Less 6 to 20 21 to 100 101 to 500 Than Maximum Average That Is Percent Aquifer County(s) of Yields gpm gpm gpm gpm 500 gpm Yield Yaeld Weighted Greater (No./%) (Nc./%} (No./%} {No./%) {No./%) (No/%) (gpm) (gpm) Average or Than20gpm Greater Hickory Blanco and 343/100 42/12.2 159/46.4 132/38.5 9/2.6 l/0.3 790 40 22 41 Gillespie Mid-Cambrian Blanco and 34/100 6/17.6 17/50.0 11/32.4 0/0 0/0 60 20 53 32 Gillespie EllenburgerBlanco and 585/100 45/7.7 217/37.1 263/44.9 56/9.6 4/0.7 1,500 65 19 55 San Saba Gillespie Marble Falls Blanco and 32/100 10/31.3 10/31.3 9/28.0 3/9.4 0/0 200 35 25 37 Gillespie ----------------------------------------------------Lower Trinity Bandera, 41/100 1/2.4 6/14.6 10/24.4 10/24.4 14/34.2 1,400 415 34 93 Kendall and Kerr Lower Trinity Bexar, 52/100 2/3.9 23/44.2 17/32.7 10/19.2 0/0 205 55 27 52 Coma), Hays and Travis Total Study 93/100 3/3.2 29/31.2 27/29.0 20/21.5 14/15.1 1,400 230 18 66 Lower Area Trinity Middle Trinity Bandera 72/100 3/4.2 42/58.3 17/23.6 8/11.1 2/2.8 700 70 14 38 Middle Trinity Bexar 12/100 0/0 3/25.0 6/50.0 2/18.8 1/6.2 723 135 25 75 and Medina Middle Trinity Blanco 103/100 37/35.9 54/52.4 12/11.7 0.0 0/0 90 15 28 12 Middle Trinity Co mal 62/100 2/3.2 32/51.6 24/38.7 4/6.5 0/0 250 40 27 45 Middle Trinity Gillespie 139/100 18/13.0 48/34.5 67/48.2 6/4.3 0/0 350 45 14 53

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Table 5. Approximate Distribution of Well Yields by Aquifer(continued) Distribution By Yield Catagories (gpm) By Number (No.) and Percent(%) More Weighted Percent Number 5orLe. 6 to 20 21 to 100 101 to 500 Than Maximum Avenge n.at Ia Percent Aquifer County(s) of Yields gpm gpm gpm gpm 500gpm Y.eld Yaeld Weipted Greater (No./%) (No./%) (No./%) (No./%) (No./%) (No./%) (gpm) (gpm) Avenge or Than!Ogpm Greater Middle Trinity Hays 34/100 0/0 9/26.5 14/41.2 11/32.3 0/0 500 125 32 74 Middle Trinity Kendall 128/100 21/16.4 56/43.8 41/32.0 10/7.8 0/0 350 45 17 40 Middle Trinity Kerr 55/100 4/7.3 8/14.5 27/49.1 14/25.5 2/3.6 1,000 135 18 78 Middle Trinity Travis 61/100 14/23.0 37/60.6 10/16.4 o;o 0/0 100 20 30 16 Total Middle Study 666/100 99/14.9 289/43.4 218/32.7 55/8.2 5/0.8 1,000 55 17 42 Trinity Area Upper Trinity Bandera, 36/100 14/38.8 15/41.7 5/13.9 1/2.8 l/2.8 1,000 45 11 20 Kendall, Kerr and Medina Upper Trinity Blanco, 94/100 24/25.5 57/60.6 12/12.8 1/1.1 o;o 175 20 19 14 Comal, Hays and Travis Total Study 130/100 38/29.2 72/55.4 17/13.1 2/1.5 1/0.8 1,000 25 13 15 Upper Trinity Area ------------------------------------------------Edwards Bandera, 269/100 69/25.6 178/66.2 22/8.2 0/0 o;o 60 15 42 8 Plateau Gillespie, Kerr and Medina

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Counties. Wells completed for rural domestic and/or livestock watering purposes have been reported to yield about 1 to 320 gpm. Historically, Middle Trinity'-vells used for public supply have yielded about 3 to 500 gpm, while irrigation wells have been reported to produce about 14 to 1,000 gpm. Well yields have been significantly increased by acidizing. Upper Trinity Aquifer -Approximately 55 percent of the wells to be completed in the Upper Trinity aquifer may be expected to have small yields. Only about 13 percent may yield 25 gpm or more, while 15 percent may yield more than 20 gpm. The most producdve yields can be expected to occur in Bandera, Kendall, Kerr, and northern Medina counties. Wells completed for rural domestic and/ or livestock watering purposes have been reported to yield about 1 to 71 gprn. Historically, Upper Trinity wells used for public :mpply have produced up to 175 gpm, while irrigation wells have been reported to produce up to 1,000 gpm. Edwards Plateau Aquifer -Approximately 92 percent of the wells to be completed in the Edwards Plateau aquifer may be expected to have very small to small yit:lds. About42 percent may yield 15 gpm or more, while only about 8 percent may yield 20 gpm or more. Well yields have been reported to range from 1 to 60 gpm for wells used for rural domestic and/ or livestock watering purposes. Two irrigation wells are known to have been completed in the Edwards Plateau aquifer in north-central Gillespie County. The yields of these two welL are unknown at this time. An Edwards Plateau aquifer well is used as part of the public supply for a rural residential subdivision in western County. The yield of this well is unknown at this time. Historically the t: nhancement or increase of well yield by acidizing has been accomplished with apparent success in Lower and Middle Trinity aquifer wells in Bandera, Coma!, Kendall, Kerr, and Travis Counties. \\'here the aquifer is contained in carbonate rocks or in calcareous sandstone and conglomerate, the yields and specific capacities (discussed later) of wells tapping such rocks may be increased by the controlled injection of diluted hydrochloric acid into the well bore. The acid increases the permeability of the aquifer by er.larging the openings, joints and/or solution channels in the immediate vicinity of the well bore. This process increases the effective well diameter, th :?reby increasing the yield of the well per unit of drawdown (specific capacity) (Reeves, 1967 and Reeves, 1969). Before the acidizing of a well is undertaten, it is recommended that representative samples of the water-bearing rocks from the well bore be collected and submitted for laboratmy solubility tests to determine if acidizing will be effective. Data reported for nine Lower Trinity aquifer wells indicates that acidizing provided well yields that were about 1.5 to 4.8 times greater than the well yields before acidizing. The average or mean of the well yields after acidizing was about 2.0 times greater than the average or mean of the well yields before acidizing. The median from such data indicates that the acidized well yields were about 3.1 times greater. These operations for the LowerTrinityaquiferwere reported to have used 2,000 to 30,000gallons per well of dilute hydrochloric acid. Data reported for ten Middle Trinity aquifer wells indicates that acidizing provided well yields that were about 1.5 to 5.5 times greater than the well yields before acidizing. The average or mean of the well yields after acidizing was about 2.9 times greater than the average or mean of the well yields before acidizing. The median from such data indicates that the Evaluation of the Ground-Water Resources of the Paleozoic and Cretat:eous Aquifen in the Hill Country ofCentr.al Texas July 1992 41

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E\'aluation of the Ground-Water Rewurces of the Paleozoic and Cretaceom Aquifers in th•: Hill Country of Central Texas July 1992 42 acidized well yields were about 3.5 times greater. These operations for the Middle Trinity aquifer were reported to have used 1,000 to 15,000 gallons per well of dilute hydrochloric acid. Within the study area, 287 specific capacity measurements have been reported for the Paleozoic and Cretaceous aquifers. The known duration of these specific capacity measurements varies from five minutes to more than 24 hours. The duration of pumping for some of the measurements is unknown. However, all measurements were considered and included in the number and percent distribution evaluation by aquifer provided in Table 6. The "Weighted Average Specific Capacities" calculated and shown for the Paleozoic and Cretaceous aquifers in Table 6 indicate the aquifers having the most and least productive wells. The Paleozoic aquifers in order of most to least productivity by well specific capacity are the Ellenburger-San Saba (12.9 gpm/ft) and Hickory (7.7 gpm/ft). Mid-Cambrian and Marble Falls aquifer wells are not represented because a sufficient number of specific capacity measurements are not available for such wells. The Cretaceous aquifers in order of most to least productivity by well specific capacity are the Lower Trinity ( 4.4 gpm/ft), Middle Trinity ( 4.2 gpm/ft), Upper Trinity (2.2 gpm/ft), and Edwards Plateau (0.5 gpm/ft). Some of the specific capacity measurements used in the above tabulation for Lower Trinity and Middle Trinityaquiferwe lls are post-acidized specific capacity measurements. The longer the duration of pumping time used for specific capacity determination, the more accurate and meaningful the measurement will be to evaluate the long-term performance of a well or group ofwells. Table 7 provides the distribution ofl14 selected specific capacity measurements (by aquifer) made after two or more hours of pumping time. Some of the selected specific capacity measurements provided in Table 7 for Lower Trinity and Middle Trinity aquifer wells are post-acidized specific capacity measurements. The information presented in Table 7 generally indicates the most and least productive wells by aquifer in the study area. The specific capacities of wells when properly planned and accurately measured also may be used to determine the following: ( 1) The projected well specific capacity and drawdown for various assumed well discharge rates (gpm); (2) The operating efficiency and longevity of a well on a longterm basis; (3) The results of enhancement of well performance and productivity due to well reconstruction, deepening and/ or treatment (such as acidizing); ( 4) The number of wells needed to meet current and projected water supply needs under known aquifer conditions; and (5) Under certain known conditions, an estimate of the transmissibility of the aquifer. Historically, the enhancement or increase of well specific capacity by acidizing apparently has been accomplished successfully in Lower and Middle Trinity aquifer wells. Information on three public supply wells completed in the Lower Trinity aquifer in Kerr County showed that postacidized specific capacities of the wells were 3.1 to 8.9 times greater than the pre-acidized specific capacities. Approximately 2,000 to 15,000 gallons per well of dilute hydrochloric acid were used during these acidizing operations. Comparison of specific capacities for acidized and non-acidized Lower Trinity aquifer wells in Bandera County indicates that the acidized wells had specific capacities which may have been about 8.6 to 10.3 times greater than the specific capacities of the non-acidized wells. A similar comparison for Middle Trinity aquifer wells in Kerr County indicates that acidized specific capacities may have been about 4.6 to 5.6 times greater.

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E\'aluation of the Ground-Water Rewurces of the Paleozoic and Cretaceous A9uifers in the Hill Country ofCcntr.al Texas July 1992 Table 6. Approxim•ate Distribution of Well Specific Capacities Without Duration Time Considered Distribution by Specific Capacity Catagories (gpm/ft) By Number (No.) and Percent(%) Weighted Percent Number of 0.9or 20.0 or Maximum Average That Is Percent Specific Less 1.0 to •l.9 5.0 to 19.9 more Specific Specific Weighted Greater Aquifer Capacities gpm/ft gpm/ft gpm/ft gpm/ft Capacity Capacity Average Than (No./%) (No./%) (No./%) (No./%) (No./%) (gpm/ft) (gpm/ft) or Greater 0.9gpm/ft Hickory 6/LOO 1/17 4/66 0/0 1/17 35.9 7.7 17 83 Elenburger27;100 9/33 9/33 4/15 5/19 85.0 12.9 19 67 San Saba Lower Trinity 47;100 25/53 11/24 8/17 3/6 30.2 4.4 26 47 Middle Trinity 177/100 101/57 49/28 22/12 5/3 107.1 4.2 17 43 Upper Trinity 21!100 15/72 3/14 3/14 0/0 16.0 2.2 14 28 Edwards Plateau 9/lOO 7/78 2/22 0/0 0/0 3.0 0.5 33 22 Table 7. Approximate Distribution of Well Specific Capacities Having a Duration Time of Two Hours or More Distribution by Specific Capacity Catagories (gpm/ft) By Number (No.) and Percent(%) Weighted Percent Number of 0.9or 20.0 or Maximum Average That Is Percent Spedfic Less 1.0 to 4.9 5.0 to 19.9 more Specific Specific Weighted Greater Aquifer Capacities gpm/ft gpm/ft gpm/ft gpm/ft Capacity Capacity Average Than (No./%) (No./%) (No./%) (No./%) (No./%) (gpm/ft) (gpm/ft) or Greater 0.9gpm/ft Hickory 4/100 1/25 2/50 0/0 1/25 0.2-35.9 4.0 25 75 Ellenburger15/100 0/0 7/46 4/27 4/27 1.5-51.1 14.1 27 100 San Saba Lower Trinity 22;'100 ll/50 4/18 2/9 0.1-30.2 5.3 27 50 Middle Trinity 57;'100 28/49 18/32 9/16 2/3 <0.1-107.1 5.2 19 51 Upper Trinity 10;100 8/80 2/20 0/0 0/0 <0.1-2.5 0.4 30 20 Edwards Plateau 6/100 5/83 1/17 0/0 0/0 <0.1-3.0 0.4 17 17 43

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E\dluation of the Ground-Water Resou -ces of the Palemoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Construction of Wells 44 The increase of well yield and specific capacity by acidizing of Paleozoic aquifer wells has not been knowingly practiced in the study area. However, since the Ellenburger-San Saba and the Marble Falls aquifers are contained in carbonate rocks, it would seem feasible that under certain conditions acidizing of wells in these aquifers may increase well yields and specific capacities. Since the water-bearing rock of the Hickory sandstone is usually cemented with siliceous material, it is not possible to readily increase well yield and specific capacity by acidizing. However, some water-bearing Hickory sandstone having carbonate cement may be encountered locally, and may be effectively acidized with dilute hydrochloric acid. Significant portions of the water-bearing rocks of the Mid-Cambrian aquifer (Welge and Lion Mountain sandstones) have quartz and siliceous (glauconitic) sand grains cemented with calcium carbonate. Under these conditions Mid-Cambrian aquifer well yield and specific capacity may be increased effectively by acidizing with dilute hydrochloric acid. The enhancement ofHickory aquifer well yields and specific capacities by controlled downhole blasting may have been accomplished successfully in Mason and McCulloch Counties northwest of the study area. Such downhole blasting only should be done with extreme caul.ion and by qualified and experienced personnel. Apparent success has been achieved by using carbon dioxide as an injection fluid to enhance water well production. This method of well development has been used to increase oil and gas well production, and uses the three forms of carbon dioxide (vapor, liquid and solid) as the injection fluid which is injected under pressure into the well bore and water-bearing formation. After the well is pressurized for a period of time, the pressure is released and the carbon dioxide and water flows from the well. This process through agitation and chemical reaction removes drilling mud and other foreign material from the well bore and waterbearing formation, and thus increases well productivity. The enhancement and longevity of well yield and specific capacity can be achieved by proper gravel packingofwellsduringtheirconstruction. Only a very few large-capacity wells in the study area were reported to have been constructed using the gravel-pack method. Proper gravel packing along with the related proper means of well completion and development can prevent the production of excessive sand and other finer material which readily damages well pumps, and can prevent the plugging of the well by such sand and finer material. Proper gravel packing and related well completion and development should be used for the construction of future large-capacity wells to be completed in the incompetent unconsolidated or semi-consolidated water-bearing sands and sandstones expected or encountered in the Hickory, Mid-Cambrian, and Trinity Group aquifers. The methods used for the construction of water wells are very important in light of the demand for more efficiently productive wells and for the assurance and protection of acceptable ground-water quality provided by the wells on a long-term basis. The six basic types of well construction historically used in the study area are shown in Figure 10. These basic types

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of well construction were determined by the evaluation of the well records presented in Reeves and Lee (1962), Mount (1963), Reeves (1969), Follett (1973), Walker (1979), Ashworth (1983), and Brune and Duffin (1983), and by the evah.:cation of more recent well data in the files of the Texas Water Development Board. A few of the recorded, shallow wells completed in the outcrops of the Paleozoic aquifers used the type of well construction diagramed as Well I on Figure 10. Some of these shallow dug wells were reported to have only "open end" completion where the 'Total Depth" of the well was at the bottom of the sealed rock or brick lining. These dug wells have large diameters ranging from 3 6 feet, and are now rarely completed and used because of potential sanitary hazards. The most common types of basic well construction that have been used to drill and complete wells in the Paleozoic aquifers are Wells II and III in Figure 10. The diameters of the well casings in rural domestic and/or livestock watering wells range from 4 to 8 inches. Public supply and irrigation wells constructed like Well II commonly have casing diameters of 7 to 10 inches. Large-capacity wells constructed and used for public supply purposes, and having construction like Well III have used large casings with diameters of 10 to 16 inches and smaller casings with diameters of 7 to 12 inches. The open hole type of completion of Wells II and III can be effectively used in most Paleozoic aquifer wells because the aquifers are composed of very competent, consolidated carbonate rocks and sandstones. However tests conducted in Gillespie County on a large-capacity Hickory well with open hole completion similar to Well II indicated the production of an undesirable amount of sand during a desired high yield. To avoid this undesirable production of sand, the well could have been initially constructed, or re-constructed, like Wells IV or Vand properly gravel packed to obtain the desired higher yield. One Hickory well used for public supply purposes in Gillespie County was reported to have the type of construction similar to Well VI in Figure 10. The annulus portion ofthe well indicated by the asterisk(*) was reported to have been gravel packed. This is one of the very few wells in the entire study area reported to havt: been gravel packed during its construction. The similar annulus areas for Wells IV and V, which are marked with asterisks(*), could be considered for effective gravel packing, if such construction is determined to be needed to provide a desired higher well yield. As indicated previously, proper gravel packing oflarge-capacity Hickory and perhaps Mid-Cam brian wells constructed like Wells IV, V and VI can avoid the production of undesirable amounts of sand and provide much higher well yields and specific capacities on a long-term basis. The Cretaceous aquifer wells are constructed similar to Wells I through VI in Figure 10. A few shallow dug wells like Well I are found completed in the outcrop areas of 1:he Upper Trinity and Middle Trinity aquifers. These dug wells have of 2 to 5 feet. The most common type of well construction used for Cretaceous aquifer, rural domestic and/or livestock watering wells is 'Nell II. Usually these wells have casing diameters of 4 to 8 inches. If caving of shale and clay is expected, wells similar to Wells III, IV and V are drilled and completed. Ev.tluation of the Ground-Water Re10urce• of the Paleozoic and Cretaceou• Aquifers in the Hill Country ofC.cntral Texa• July 1992 45

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Evaluation of the Ground-Water Re ;ources of the Paleozoic and Cretaceom Aquifers in the Hill Country of Central Texas July 1992 46 Sealed Rock or 8 rick -in in g as Casing Cemented WELL JI (Drilled Well) Annulus -------= Seal-------------u > <' 0 pen Hole )) <' Open <_ ---........ 1--------Total Depth ______ ___..,.,.___ ____ ') WELL III (Drilled Well) WELL N (Drilled Well) --.... Land Surface ..,. Large Casing (> i:-::[[ \-(. . Smaller )-. Casing (•' --...-----Seal Cemented Annulus :> ---Open Hole Tot a I 0 e p t h WEL_ -:sL (Drillecl Well) Casing ---------,11--. Cemented Annulus _______ ..,. WELL ::szr (Drilled Well) Land Surface ______ _...,._ Casing Cemented Smaller Casing or with Selected Perforated, Slotted Screened Intervals Cos in g Cemented Annulus ------... Casing with Selecte Perforated, or Screened lnterv-=-..,...-Seal 0 pen HoI e --------i-T ot a I Depth -------'--------____J Figure 10 DIAGr::(AMS SHOWING TYPES OF WELL CONSTRUCTION

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About 95 percent of the existing wells that are completed in the Edwards Plateau aquifer in Bandera, Gillespie, and Kerr Counties are completed open hole in a n1anner similar to Well II in Figure 10. Most of these wells have casing diameters of6 or 7 inches. About 75 percent of these wells were completed before 1950, and about 65 percent have the casing set at a depth ofless than 10feet (Reeves and Lee, 1962; Reeves, 1969; and Walker, 1979). Most of these wells probably do not have the casing properly cemented to provide an adequate seal from potential surface and shallow subsurface sanitary hazards. Most of the completed in the Upper Trinity aquifer have construction similar to Well 11 in Figure 10, commonly have casing diameters of 6 to 8 inches, and are used for rural domestic and livestock watering purposes. The major well c:onstruction consideration for Upper Trinity aquifer wells is the amount (length) of casing that needs to be set and the proper cementing of st:.ch casing in the borehole. In most of the study area, the Upper Trinity aquifer has highly mineralized water commonly found in two evaporite zones. When completing wells, these zones need to be cased-off and the casing properly cemented. Wells similar to Wells II, III, IV and V in Figure 10 are usually constructed as Middle Trinity aquifer wells for municipal and industrial water supply purposes. These wells most commonly have minimum casing diameters of 4 inches and maximum casing diameters of 12 inches. It is very important that Middle Trinity aquifer wells have properly set and cemented casings to avoid production of any highly mineralized water that may be encountered in the overlying: evaporite zones of the Upper Trinity aquifer. Lower Trinity aquifer wells in Kerr, Kendall, and Bandera Counties are constructed with open hole completion like Wells II and III in Figure 10. The Sligo and Hosston mem hers of the Travis Peak Formation (Table 1) in these areas are sufficiently competent and consolidated so tbat high well yield with open hole completion can be achieved. The casings in these wells need to be set and cemented to a depth below the base of the Hammett membertoavoi:lcavingfrom the Hammettandotheroverlyingincompetent and unconsolidated strata, and to avoid production of water from the evaporite zones of the Upper Trinity aquifer. Those wells for public supply purposes usuary have large casing diameters of 16 to 20 inches and smaller casing diameters of8 to 12 inches. The Hosston member in Hays and Travis Counties is usually found to be incompetent and in part unconsolidated. In these areas, wells are constructed similar to Wells IV and Vwith large casing diameters of 10 to 12 inches and smaller casing diameters of 6 to 8 inches. Well VI in Figure 10 illustrates well construction commonly used to produce water from both the Middle Trinity aquifer and the Lower Trinity aquifer. The casing with selected perforated, slotted, or screened intervals is set opposite the Middle Trinity aquifer, while the open hole interval is positioned opposite the competent and consolidated water-bearing rocks of the Lower Trinity aquifer (Sligo and Hosston members). The lower seal is required to prevent filling of the open hole portion of the well by incompetent rock material from the Hammett member. The casing above the perforated, slotted or intervals opposite the Middle Trinity aquifer should be properly cemented to prevent production of water from the evaporite zones of the Upper Trinity aquifer. Evaluation of the Ground-Water Rel!Ources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 47

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in de Hill Country of Central Texas July 1992 Water-Level Changes 48 The dark shaded casing or liner shown on Wells IV, V, and VI in Figure 10 indicates that portion of the well open to the aquifer. These dark shaded portions of casing or liner may be selectively perforated, slotted or screened at two or more depth intervals within specific selected portions ofits entire length, or may be perforated, slotted, or screened within one continuous depth interval throughoutmostofitsentire length. Only a veryfewofthese type of wells which have been completed in the Cretaceous aquifers were reported to be gravel packed. Such gravel packing could be accomplished in these wells by placing gravel in the annulus areas marked with an asterisks (*). Since these types of well construction are used in those portions of the Trinity Group aquifers which are expected to have very fine grained, incompetent and unconsolidated deposits, a properly sized, sorted and installed gravel pack should be considered as a means to enhance well productivity and longevity. Wells II through VI shown in Figure 10 should be properly cemented using gravity and/ or pressure cementing methods and procedures. Proper cementing of a well provides reasonable assurance that undesirable waters from various adjacent surface and subsurface sources will not enter the well and contaminate the ground-water discharged by the well. The casings, liners and screens used in the construction of wells should be made of material that will be reasonably resistant to corrosion and avoid mechanical failures. Most wells in the study area use steel casings and liners or metal screens in wells constructed similar to Wells IV, V, and VI in Figure 10. The main advantage in the use of metal casings, liners and screens is that they provide great strength and durability; especially during the cementing phase of well construction in the deeper wells. Plastic casings, liners, and screens may be used to construct wells, but caution should be used during their installation. The use of plastic materials should be limited according to some specific well depth, because plastic well materials are not as strong as metal materials. Also certain plastic casings that are in tended to be cemented are known to become distorted and buckle during and soon after the cementing phase ofwell construction. It has been reported that certain plastic casings will develop such a problem due to the heat generated by certain types of cement during the placement and curing of the cement in the well bore annulus. Compatible plastic casing and cements should be used to avoid this problem. Well drillers, well operators, and well owners should use and practice the principles,,methods,andproceduresdescribedforwelldesign,construction, and operation provided in Driscoll (1986). Those persons or entities needing a well drilled should use a water well driller registered with the Texas Water Commission. Under natural conditions without withdrawals by wells, water-level changes in an aquifer are caused by the changes of the natural recharge-discharge conditions of the aquifer. When the amounts of natural recharge and natural discharge are the same and balanced, water-level changes in the aquifer are essentially negligeable. However, when natural recharge is reduced during dry periods, water is discharged naturally from transit storage and water levels decline accordingly. When the aquifer again is replenished by adequate rainfall, the volume of water drained from transit storage is replaced and water levels will rise accordingly. Withdrawals by

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wells disrupt this natural condition and artificially cause various water-level changes. Coupled with the natural changes of recharge-discharge conditions described above, the amount and extent of water-level changes depend on the frequency, amount, and distribution of the withdrawals by wells, and the amount and distribution of the aquifer's, coefficients of transmissibility and storage which control the flow and availability of water to replenish the withdrawals by wells. Mount ( 1963) appropriately describes these and other conditions which cause water-level changes. Very few water-level observation wells were available to this study to evaluate the net changes in water-levels in the Paleozoic aquifers. Those net water level changes detected or estimated for the Hickory, Ellenburger-San Saba and Marble Fa1ls aquifers for the 1977-1987 period are shown on Figure 11 which also provides the elevation of the water-level in 1987. Maximum net water-level declines detected or estimated for the 1977-1987 period were about 19 feet in the Hickory aquifer (north ofFredericksburg, north-central Gillespie County), about 32 feet in the Ellenburger-San Saba aquifer (southeast of johnson City, central Blanco County), and about 6 feet in the Marble Falls aquifer (near Cypress Mill, eastern Blanco County). Longterm net water-level declines detected in the Hickory and Ellenburger-San Saba aquifers are provided in Table 8. A significant amount of data is available to evaluate the net water-level changes from 1977 to 1987 in the Trinity Group aquifers within the study area. Those net water-level changes detected or estimated for the Lower Trinity aquifer for the 1977-1987 period are shown on Figure 11. Those 1977-1987 net water-level changes for the Middle and Upper Trinity aquifers are shown on Figure 12. Figures 11 and 12 provided the elevations of the water-levels of the Lower, Middle and Upper Trinity aquifers in 1987. Sufficient water-level data was available to approximately contour the elevation of the 1987 water-level of the Middle Trinity aquifer as shown on Figure 12. A summary of the approximate net water-level changes in the Trinity Group aquifers from 1977 to 1987 is provided in Table 9. The approximate statistical distribution of these 1977-1987 net water-level changes in the Trinity Group aquifers by rise and decline range catagories is given in Table 10. Maximum net water-level declines detected or estimated for the 1977-1987 period were about 155 feet in the Lower Trinity aquifer (at Bandera, Bandera County), about 59 feet in the Middle Trinity aquifer (near Comfort in eastern Kerr County), and about 16 feet in the Upper Trinity aquifer (southwest of Bandera, Bandera County). Although net water-level rises occurred in some parts of the study area during the 1977-1987 period, net water-level declines in the Trinity Group aquifers significantly out-weighted net water-level rises in both areal distribution (Figures 11 and 12) and statistical distribution (Table 1 0). The most significant, long-term, net water-level changes detected or estimated for the Trinity Group aquifers are provided in Table 11. Very few water-level measurements in observation wells completed in the Edwards Plateau aquifer were available to this study. The elevation of the 1987 water leveh and the net changes in the water levels of the aquifer from 1977 to 1987 are shown for four wells on Figure 12 in Bandera and Kerr Counties. Measurements and estimates ofwater levels in twowe1ls indicated net water-level rises, while measurements and estimates in two other wells indicated net water-level declines. Evaluation or the Ground-Water Resources or the P..deozoic and Cretaceous Aquifers in the Hill Country or Central Texas July 1992 49

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Evaluation of the Ground-Water Res->urces of the J>;deozoic and Cretaceous Aquifers in the Hill CountryofCcntr.otl Texas July 1992 50 To gain a visual perspective on the water-level changes detected and estimated in the Paleozoic and Cretaceous aquifers, the reader is referred to Figures 13 through 18. These illustrations show hydrographs for the water levels measured and estimated in selected water-level observation wells completed in the Paleozoic and Cretaceous aquifers. Water-level measurements from observation wells were not available for such illustrations for Comal and Medina Counties. The significant long-term water-level declines that have been detected in the Hickory and Ellenburger-San Saba aquifers were mainly caused by concentrated ground-water withdrawals coupled with deficient transmissibilities of the aquifers. Lack of saturated sand thickness and probably barriers due to faulting have caused water-level declines in the Hickory aquifer. Deficient transmissibility due to lack of extensive lateral and vertical development of solution openings have caused water-level declines in the Ellenburger-San Saba aquifer. Concentrated ground-water withdrawals coupled with deficient transmissibility are the cause of the greater long-term water-level declines that have been detected in the Trinity Group aquifers, particularly in the Lower and Middle Trinity aquifers. The amount and distribution of transmissibilities of the Lower Trinity aquifer especially are highly variable, ranging from as high as 15,000 to 25,000 gpd/ft in Kerr and Bandera Counties to as low as 140 to 1,900 gpd/ft in Travis County (Ashworth, 1983, Brune and Duffin, 1983, and Guyton, 1973). The moderate to extremely low transmissibilities of the Paleozoic and Cretaceous aquifers make it extremely difficult to economically develop and use the relatively large ground-water reserves without adverse long-term water-level declines in and near of concentrated pumpage.

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Table 8.-App•oximate Long-Term Net Water-Level Declines in the Hickory and FJienburger-San Saba Aquifers Aquifer Hickory Location and Explanation As Needed Northwestern Blanco County Well :57-37-402 west of Round Mountain Ellenburger-Central Blanco San Saba County Well !)7-45-903 just east of Johnson City Hickory North-Central Gillespie County 'Veil 57-41-301, City of F'redericksburg Well Hickory North-Central Gillespie County \Vell57-42-101 near City of Fredericksburg Vvell ElJenburgerS-outh-Central Gillespie San Saba County \Veils 57-50-102 and 104 in the City of Fredericksburg's Pedernales River \\'ell Field Period (Yean) 1968-1987 1938-1984 1962-1985 1953-1987 1939-1986 Approximate Net Water-Level Otange Decline Rate of Decline (Feet) (Feet/Year) 2.7 0.1 5.6 0.1 51 2.2 108 3.2 26 0.6 Evaluation or the Ground-Water Resource! or the Paleozoic and Cretaceou5 Aquiren in the Hill Country or C-entral Texa5 July 1992 51

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Evaluation of the Ground-Water Re!ources of the Paleozoic and Cretaceo.u Aquifers in the Hill Country of Central Texas July 1992 Table 9. Summary of Approximate Net water-Level Changes in theTrinity Group Aquifers, 1977-1987 1977-1987 1977-1987 Percent Range in Net Average Net Average Ratio of Nwnberof Change Observed Change or Rises to Aquifer Observations Rise ( +) Decline (-) Rise ( +) Decline (-) Greater Declines Lower Trinity 14 +155 to -155 -5.3 64 1 to 3.7 Middle Trinity 45 +30 to -59 -8.2 33 1 to 1.5 Upper Trinity 5 +8 to -16 -3.8 40 1 to 4.0 Trinity Group 64 +155 to -155 -7.2 42 1 to 1.9 Table 10. Approximate Distributions of Net Water-Level Changes in the Trinity Group Aquifers, 1977-1987 No Rise Catejiories in Feet Decline RanQ:e CateQ:ories in Feet >25.0 10-0-25.0 2.0-9.9 0.1-1.9 Zero 0.1-1.9 2.0-7.1 7.2-25.0 >25.0 Number of ObseiVations 4 5 9 4 0 4 11 16 11 Total-22 Total-42 Approximate Percent 6.2 7.8 14.1 6.2 0 6.2 17.2 25.1 17.2 Total-34.3% Total-65.7% 52

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Evaluation of the Ground-Water Re!IOurces o the Paleozoic and Cretaceous r'2cuifers in the Hill Country of :ntral Texas July 1992 Table 11.-Approxi:mate Long-Tenn Net Water-Level Changes in the Trinity Group Aquifers Approximate Net Water-Level Change Aquifer Location/Explanation Period Decline (-), Rise(+) Rate of Change As Needed (Years) (Feet) (Feet/Year) Lower Bandera County Well 1953-1987 -271 -8.0 Trinity 69-24-202 in City of Bandera Lower Bandera County Well 1967-1987 -157 -7.9 Trinity in City ofE.andera Middle Bandera County Well 1954-1984 -84 -2.8 Trinity in City of Bandera Middle Gillespie County Well 1962-1983 -105 -5.0 Trinity and 57-41-901 in City of Hickory Fredericksburg National Guard Well Field Middle Hays County Well 1975-1986 -108 -9.8 Trinity 57-56-702 near City of Dripping Middle Ho.ys County Well 1974-1987 -2.4 -0.2 Trinity 57-702 near City of Wimberly Middle Kendall County Wells 1947-1987 -98 -2.5 Trinity 68-01-301 and 68-01-303 in City of Comfort Middle Kendall County Wells 1947-1987 -84 -2.1 Trinity and 68-01-310 in City of Comfort Middle Kendall County Well 1957-1987 -53 -1.8 Trinity 68-01-303 in City of Comfort Middle Kendall County Wells 1940-19781 -102 -2.7 Trinity 68-11-701 and 68-11-708 in City of Boerne 1978-19872 +1 +0.1 1-Before surface water was used. 2-Mter surface 1940-1987 -101 -2.1 v.ater was used. Middle Kendall County Wells 1956-19791 "12 -0.5 Trinity 68-11-412 and 68-11-715 in City of Boerne 1979-19882 +26 +2.9 1-Before surface water was used. surface 1956-1988 +14 +0.4 water was used.

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E\'aluation o the Ground-Wat•!r Resources o the! Paleozoic and Cretaceous Aquifers in the Hill Country Texas July 1992 Table I I.-Approximate Long-Term Net Water-Level Changes in the Trinity Group Aquifers (cont'd.) Approximate Net Water-Level Change Aquifer Location/Explanation Period Decline (-), Rise(+) Rate of Change As Needed (Years) (Feet) (Feet/Year) Middle Central Kendall County 1965-1986 -7.9 -0.4 Trinity Well 68-11-103 noith of Boerne Lower Eastern Kendall County 1965-1987 -12.7 -.06 Trinity Well 68-04-909 south of Kendalia near Guadalupe River Lower Cit'! of Kerrville Wells 1923-19801 -319 -5.6 Trinity 56-63-601, 603, and 604 from City Water 1980-19872 +111 +15.9 Le\el Records 1Before large scale 1923-1987 -208 -3.3 sur:ace water use 2Mter large scale sunace water use Lower City of Kerrville Well Trinity 56-63-608 1952-19761 -60 -2.5 1 Be fore large scale surface water use 1976-19872 +26 +2.4 2After large scale surface water use 1952-1987 -34 -1.0 Middle Kerr County Well 1967-1987 -26.4 -1.3 Trinity northwest of Comfort Middle Eas:ern Kerr County Well 1974-1987 -52.0 -4.0 Trinity 68-01-505 southwest of Comfort Middle Southeastern Kerr County 1959-1987 -58.9 -2.1 Trinity Wel169-16-201 between Center Point and Bandera Lower tern Travis County Well 1967-1987 -49.6 -2.5 Trinity 58-2-403 southeast of Lago Vista Lower Western Travis County Well 1971-1988 -12.7 -0.7 Trinity 58-41-101 northwest of Bee Cave Lower Travis County Well 1949-1986 -154 -4.2 Trinity 58-42-502 at St. Stephens School northwest of Austin 54

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The chemical constituents in ground water are dissolved from the soils and rocks as water percolates from the land surface through the unsaturated zone and into the saturated zone of an aquifer. Rainfall is relatively free of minerals but is inherently slightly to moderately acidic (pH less than 7.0) which makes it a very effective salven t. As water !'lowly percolates downward under the influence of gravity to and through an aquifer, it dissolves some of the minerah. in the soil and rocks at a relatively consistent rate and in an accumulative manner. Also, as the water percolates to and through an aquifer, it may encounter pollutants introduced by the activities of man on and beneath the land surface. When pollutants are encountered, they become at various concentrations part of the water-quality regime of the aquifer, and alter the natural or ambient chemical character of the ground water. Otherimportantfactors that influence the mineralization of ground water are the length of time the water has been in contact with the rocks and any pol1utants, the solubility of the minerals and pollutants in the soils and rocks, the amount of carbon dioxide dissolved in the percolating water, the variances in the permeabilitiesofthe soils and rocks, any structural geological features (such as faults) which impede the flow of the percolating waters, and the subsurface temperature and pressure which inherently increase with the increa:;;e in depth below the land surface. The results of more than 5,800 ground-water chemical analyses for the eight aquifers within the study area were examined. Because of the very large amount of data available, only eleven important chemical constituents and characteristics were selected and considered for evaluation and description. They include nitrate, fluoride, chloride, sulfate, dissolved solids, sodium, hardness, iron, alpha radiation, and radium. In all, about 5,784 individual analysis were used, and included 876 for nitrate, 856 for fluoride, 774 for chloride, 991 for sulfate, 732 for dissolved solids, 724 for sodium, 759 for hardness as CaC03 , 41 for iron, 24 for alpha radiation, and 7 for radium. The abundance, sources, form of occurrence, concentration, significance and maximum constituent level(s) for each of these selected constituents and characteristics and other important constituents and properties of water are presented in Appendix A (Texas Water Development Board, 1989c). Figure 19 provides the concentrations of sulfate, chloride and total dissolved solids contents in the water from selected wells and springs producing from thewater-bearingunitsofthe Paleozoic and TrinityGroupaquifers (modified from Ashworth, 1983). Such information on water quality for the Edwards Plateau aquifer :is provided in Walker ( 1979). A water-quality summary for each aquifer addressing the concentrations of nitrate, fluoride, chloride, sulfate, dissolved solids, sodium and hardness as CaC03 is presented in Appendix B. These summaries do not include iron, alpha radiation, and radium because only a very limited number of analyses were available for these constituents. In addition, detailed evaluations were made: E'"dluation of the Ground-Water Re!IOurces of the Paleozoic and Cretaceous A9uifers in the Hill Countr)'ofCentral Texas July 1992 CHEMICAL QUALI1Y OF I GROUND WATER _ 71

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Ev-.tluation of the Ground-Water ReK urces of the Paleozoic and Cretaceou• Aquifers in the Hill Country of Central Texas July 1992 72 1) to determine the statistical and areal (by county) distribution of nitrate, fluoride and sulfate concentrations detected in each of the eight aquifers, using the most recent analyses made during the historical period from the late 1930's to the mid 1980's, and 2) to determine the changes in nitrate concentrations de tee ted in each aquifer during the historical period from the late 1930's to the mid-1980's. Information on the distribution in the concentrations of nitrate, fluoride and sulfate was compiled for each aquifer as provided respectively in Appendices C-1, C-2 and C-3. These specific constituents were addressed because of the abundance of analyses available for these constituents and because of their importance as significant indicators to determine if a ground-water source has water-quality problems and if it is capable of meeting primary and secondary drinking water standards (Texas Department ofHealth, 1988b). An unusually or excessively high concentration of nitrate, above the approximate ambient level concentration for a specific aquifer, is a significant and reasonably reliable indicator of pollution from human or animal wastes and/or ranching and farming activities. Unusually or excessively high concentrations of nitrate in ground water can be caused by the dissolution of nitrate minerals which may exist naturally in the rocks within or adjacent to the aquifer. Not any of the geological units are known to have high concentrations of such nitrate minerals within the study area. However, nitrate mineral have been found in faulted and fractured rocks of the Ellenburger Group in San Saba County north of the Llano uplift. Figures 20,21 and 22 provide visual distributions of these detected historical nitrate concentrations by range in concentration catagories for each of the eight aquifers. The nitrate range in concentration category sym bois used on these maps are intended to provide a visual perspective on where and to what degree each aquifer has nitrate pollution within the study area. Such pollution is readily indicated locally for certain urbanized areas for the Trinity Group aquifers and some of the Paleozoic aquifers (Figures 20, 21 and 22). Also, it is very apparent that the Edwards Plateau aquifer has widespread nitrate pollution in the rural portion of western Gillespie County and northwestern Bandera County (Figure 21). Similar, but more local, rural nitrate pollution of some of the Paleozoic aquifers in Blanco and Gillespie Counties is indicated on Figure 20. Table 12 which was prepared from information in Appendix C-1 is a summary of the percent distributions of nitrate concentrations by aquifer. A numerical rating of these nitrate concentration distributions by aquifer provides an approximate indicator of the apparent most and least nitrate pollution by aquifer. In the order of most to least nitrate pollution, the aquifers are rated as follows: Marble Falls AquiferHas very serious nitrate pollution in the Cypress Mill area of eastern Blanco County. Similar nitrate pollution is also apparent in the Honeycut Bend area east of Johnson City in eastern Blanco County (Figure 20).

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Table 12. Summary of Percent Distributions of Nitrate Concentrations by Aquifer Percent Distributions Aquifer ExceedMCL Exceed Regional Exceed Ambient of44.3 mg/1 Average of 10.6 mg/1 Level of 1.0 mg/1 Hickory 2.9% 14.3% 45.7% Mid-Cambrian 9.7% 41.9% 77.4% Ellen burger-San Saba 5.4% 37.8% 78.4% Marble Falls 27.3% 90.9% 100.0% Lower Trinity 2.3% 9.1% 34.1% Middle Trinity 2.8% 12.1% 42.6% Upper Trinity 2.2% 9.6% 53.3% Edwards Platt:au 9.5% 312.4% 73.3% Mid-Cambrian Aquifer-Serious nitrate pollution detected in rural area west-northwest of Round Mountain in northern Blanco County and in a rural area north of the Pedernales River and west of U.S. Highway 281 in west-central Blanco County (Figure 20). Ellenburger-San Saba AquiferHas moderate nitrate pollution detected along Pedernales River from U.S. Highway 290 bridge southeast of Fredericksburg in Gillespie County to Johnson City in Blanco County. Serious nitrate pollution is evident at Johnson City in Blanco County (Figure 20). Edwards Plateau Aquifer-Has serious nitrate pollution in widespread rural area ofwestern and central Gillespie County; particularly in area north of U.S. Highway 290. Similar nitrate pollution is indicated in a rural area of northwest Bandera County (Figure 21). Hickory Aquifer-Has serious nitrate pollution in a local area adjacent to FM Highway 1323 in northwest Blanco County. Moderate nitrate pollution is evident in local areas north ofFredericksburg between U.S. Highway 87 and State Highway 16 (Figure 20). Middle Trini1;y Aquifer -Has serious to moderate nitrate pollution in urbanized areas at and near Comfort (Kendall and Kerr Counties), Blanco (Blanco County), Kendalia (Kendall County), Berghiem (Kendall County), and Boerne (Kendall County). Also, has serious nitrate pollution in local rural areas of Gillespie and Blanco Counties (Figure 22). Upper Trinity AquiferMost serious nitrate pollution in local rural areas of northern Kendall and northern Hays Counties. Moderate pollution found in urbanized area at and near Blanco (Blanco County) and Dripping Springs (Hays County). Also, moderate pollution found in urbanized area just north of U.S. Highway 290 between State Highway 71 and Travis-Hays County line in southwest Travis (Figure 21). LowerTrinityAquifer-Serious nitrate pollution found in generally urbanized area along Pedernales River arm of Lake Travis in western Travis County (Figure 21). Ev-.lluation of the Ground Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 81

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EV'.1luation of the Ground-Water Resour•:es of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 82 Most of the nitrate pollution described above has occurred in those portions of the respective aquifers nearest to the land surface. The nitrate pollution in urbanized areas probably is attributed to septic tank discharges, while the nitrate pollution in rural areas probably is attributed to animal waste and/ or septic tank discharges. Uvestock and other animal wastes probably are the main cause for the widespread nitrate pollution of the Edwards Plateau aquifer detected in western Gillespie County and northwest Bandera County (Figure 21). Other animal wastes may include excrements produced by wildlife on the land surface by bats in caves which occur in the carbonate rocks above the zone of saturation of the Edwards Plateau aquifer. Changes in nitrate concentrations in the ground waters from one year to another for the historical period from the late 1930's to mid-1980's was evaluated for 162 wells. Available data indicate a general decrease in nitrate concentrations in the ground water analyses evaluated for the Paleozoic and Trinity Group aquifers. Of the 20 Paleozoic wells sampled during various time periods, three wells or 15 percent had significant increases in nitrate concentration, 16wells or 80 percent had significant decreases and one well or about 5 percent had no change. Of the 124 Trinity Group aquifer wells sampled during various time periods, 33 wells or 27 percent had significant increases in nitrate concentration, 79 wells or 64 percent had significant decreases and 12 wells or 9 percent had no change. The Edwards Plateau aquifer which has widespread nitrate pollution had very significant increases in nitrate concentrations during various periods from the late 1930's to the mid-1980's. Of the 18 Edwards Plateau aquifer wells sampled, 16 wells or 89 percent had significant increases in nitrate concentration and two wells or 11 percent had decreases. These results are somewhat suspect, because the accuracies of the methods and procedures used for sampling and analyzing waters for nitrate changed considerably during the 1930's to mid-1980's period. Information on the concentrations of fluoride in the ground waters of the eight aquifers in the study area is provided by aquifer in the water quality summaries in Appendix B. Appendix C-2 provides the distribution of fluoride concentrations by range in concentration catagories, averages and medians by county for each of the eight aquifers. The unusually high to excessive concentrations of fluoride detected in the ground waters of the Trinity Group aquifers (Appendix C-2) are present due to the dissolution of naturally occurring fluoride minerals within some of the sedimentary rocks of the Trinity Group. Such unusually high to excessive concentrations of fluoride are readily detected in the deeper portions of the Trinity Group aquifers; particularly in the Lower Trinity aquifer in Travis and Bandera Counties, the Middle Trinity aquifer in Travis, Hays, Bandera, Kendall and Kerr Counties, and the Upper Trinity aquifer in Travis, Hays and Bandera Counties. Such inherent concentrations of unusually high to excessive concentrations of fluoride were also detected in the Mid-Cambrian aquifer in Blanco and Gillespie Counties. The 77 4 analyses evaluated for chloride concentrations in the eight aquifers indicate that chloride does not pose significant problems in the use of ground waters for public supply, manufacturing and irrigation purposes. Information on the concentrations of chloride in the ground waters of the study area is provided in Appendix B. The concentrations of chloride detected in the ground waters from selected wells and springs producing from the various water-bearing rocks of the Paleozoic and Trinity Group

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aquifers are provided on Figure 19. Such information on chloride in the Edwards Plateau aquifer is provided in Figure 16 in Walker (1979). Information on the concentrations of sulfate in the ground waters of the eight aquifers is provided by aquifer in the water quality summaries in Appendix B. Appendix C-3 provides the distribution of sulfate by range in concentration catagories, averages and medians bycountyforeach of the eight aquifers in the study area. The concentrations of sulfate detected in the ground waters from selected wells and springs producing from the various water-bearing rocks of the Paleozoic and Trinity Group are provided on Figure 19. Such information on sulfate in the Edwards Plateau aquifer is provided on Figure 16 in Walker (1979). The predominant sulfate minerals found in the sedimentary rocks of the study area are anhydrite and gypsum. Large deposits of these minerals are found as prominent evaporite beds within the upper unit of the Glen Rose Formation (Table 1). Thin layers of gypsum and anhydrite are found in the Cow Creek member of the Travis Peak Formation (Table 1). Most of the other sedimentary rocks of the Trinity Group probably contain very small to moderate amounts of anhydrite and gypsum; particularly the marls, shales and clays of the Glen Rose Formation and the shales and clays of the Travis Peak Formation. The unusually high to excessive concentrations of sulfate detected in thegroundwatersofthe UpperTrinityaquifer (Appendix C-3) are due to the dissolution of the prominent evaporite beds within the upper unit of the Glen Rose Formation. The unusually high to excessive concentrations of sulfate detected in the Middle Trinity aquifer (Appendix C-3) is probably caused by the existence and dissolution of the thin beds of anhydrite and gvpsum found in the Cow Creek member of the Travis Peak Formation. Some of the unusually high to excessive concentrations of sulfate detected in theTrinityGroupaquiferscan be avoided by proper well construction. If the prominent anhydritte and gypsum beds of the upper unit of the Glen Rose Formation and in some cases the thin layers of anhydrite and gypsum of the Cow Creek member are not prevented from supplying ground waters to wells, waters pumped from such wells will contain unusually high to excessive concentrations of sulfate. Also, improperly sealed, cased, and cemented boreholes which pass through the upper unit of the Glen Rose Formation are conduits of high sulfate ground waters which leak downward and readily contaminate the relatively low sulfate waters produced from portions of the Middle Trinity aquifer and/ or from the Lower Trinity aquifer. Most of the concentrations of dissolved solids detected are due to the related high concentration of sulfate; particularly in the Trinity Group aquifers. Dissolvc::d solids is included in the water-quality summary for each aquifer in Appendix B. The concentrations of dissolved solids detected in the ground waters from selected wells and springs producing from the various water-bearing rocks of the Paleozoic and Trinity Group aquifers are provided on Figure 19. Such information on dissolved solids in the Edwards Plateau aquifer is provided on Figure 16 in Walker ( 1979). Sodium is included in the water-quality summary for each aquifer in Appendix B, because of its apparent effect on human blood pressure and irrigated soils. Excessive sodium concentrations are believed to cause high blood pressure; consequently, a maximum level concentration of20 mg/ I in drinking water is recommended for most persons having high blood pressure (Lappenbusch, 1988). All of the eight aquifers have ground Evaluation of the Ground-Water Resources of the Paleozoic July 1992 83

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E\'llluation of the Ground-\\'ater Re!IOurcc:s of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 84 pressure (Lappenbusch, 1988).Alloftheeightaquifershaveground waters with an average sodium concentration of 20 mg/1 or more. The greatest average concentrations above the 20 mg/1 were determined for the Lower Trinity (183 mg/1), the Hickory (60 mg/1), the Middle Trinity (49 mg/1) and the Mid-Cambrian (46 mg/1) aquifers. The highest concentrations of sodium were found generally in the deeper wells completed in these sandstone aquifers. Ground waters with lower average concentrations of sodium at or slightly greater than 20 mg/1 were determined to be in the carbonate rocks of the Edwards Plateau (20 mg/1), Marble Falls (21 mg/1), Ellenburger-San Saba (24 mg/1) and Upper Trinity (26 mg/1) aquifers. A high sodium content has been found to limit the use of water for irrigation because excessive concentrations are known to impair the tilth and permeability of the soil (See "Sodium", "Percent Sodium", "Sodium Adsorption Ratio" and "Residual Sodium Carbonate" in Appendix A). Calculations of the sodium hazard for the ground waters of the Paleozoic and Cretaceous aquifers indicate no significant problems with use of such waters for irrigation of the soils. Only ten deep wells produced waters having a significant sodium hazard. These wells consisted of three deep Hickory wells in Blanco County and seven deep Lower Trinity wells in Bandera (2 wells) and Kendall (5 wells) Counties. A majority ofthese wells had depths greater than 1,000 feet. Hardness as CaC03 is included in the water quality summary for each aquifer in Appendix B. All of the ground waters analyzed are inherently hard to very hard. For more information on the hardness of ground water, please refer to Appendix A. Only a limited number of historical iron analyses were available. The 41 available analyses had iron concentrations which ranged from 0.0 to 9.9 mg/1 with 41 percent exceeding the secondary drinking water standard MCL of 0.3 mg/1 for iron, and 24 percent exceeding the average iron concentration of 1.1 mg/1 for all ground waters analyzed for iron. The available data and the above evaluation for iron should be considered inconclusive as to whether ground waters in the study area have serious iron problems. Future analyses for iron should be made by using correct water sample collection, treatment and transport methods and procedures to assure that the water sampled will have iron concentrations representative of the waters in the aquifers. Other than natural iron content of the aquifer, high iron concentrations in water may be derived from well casings, pipes, pumps, storage tanks and other cast iron and steel water delivery facilities and equipment. Avery limited number of selected radioactive analyses of the ground waters in the study area were made. Those limited radioactive analyses made include 24 analyses for alpha radiation and 7 analyses for total radium which includes radium-226 plus radium-228. The results of the limited number of analyses for alpha radiation are as follows: ( 1) Six alpha analyses made of Hickory waters in Gillespie County had a range of about 8.4 to 44 picocurries per liter (pCi/1) with an average alpha of25 pCi/1. Approximately 50 percent of the analyses exceed the average concentration of 25 pCi/1 while about 67 percent of the analyses exceed the primary drinking water standard of 15 pCi/1 for alpha.

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(2) One alpha analysis made ofMid-Cambrian water in Gillespie County had a very high concentration of about 59 pCi/1. This concentration is almost 4 times greater than the MCL of 15 pCi/1 for alpha. (3) Six alpha analyses made of Ellenburger-San Saba waters in Blanco and Gillespie Counties had a range in alpha ofless than 2.0 pCi/1 to about pCi/1 with an average concentration of about 2.1 pCi/1. ( 4) One alpha analysis made of Marble Falls water in eastern Gillespie County had a concentration of about 4.4 pCi/1. (5) Three a1pha analyses made of Lower Trinity waters in Bandera, Kendall, and Kerr Counties had a range in alpha of less than 2.0 pCi/1 to about 5.3 pCi/1 with an average concentration of about 3.8 pCi/1. (6) Seven alpha analyses which were made for Middle Trinity waters in Gillespk (3), Kendall (3), and Kerr (1) Counties had a range in alpha of less than 2.0 pCi/1 to about 11 pCi/1 with an average concentration of about 4.4 pCi/1. The highest concentration of 11 pCi/1 was in water from a Gillespie County well at Fredericksburg which is believed to produce water from both the Middle Trinity aquifer sand) and the Hickory aquifer directly underlying the Hensell sand. The results of the very limited number of analyses for total radium (radium-226 plus radium-228) are as follows: (1) Two total radium analyses made of Hickory waters in Gillespie Countyhadarangeofl6.0to 18.4pCi/lwithanaverageconcentration of about 17.2 pCi/1. The two analyses were about 3.2 to 3. 7 times greater than the MCL of 5.0 pCi/1 for total radium. (2) Two total radium analyses made of Lower Trinity waters in Kendall and Kerr Counties had a range of approximately 4.4 to 6.0 pCi/1 with an average concentration of about 5.2 pCi/1. The 6.0 pCi/1 concen:ration was detected in 1the water from a well in Kendall County at Comfort and exceeds the MCL of 5.0 pCi/1 for total radium. (3) Three total radium analyses made of Middle Trinity waters in Gillespie, Kendall, and Kerr Counties had a range of 0.6 to 10.9 pCi/1 with an average concentration of about 5. 7 pCi/1. The 10.9 pCi/1 concentration was detected in the water from a well which is in Fredericksburg, and which is believed to be completed in the Middle Trinity and Hickory aquifers. Also, a 5.3 pCi/1 total radium concentration was detected in the water from a Middle Trinity well at Ingram in Kerr County. Both of these analyses have total radium concentrations that exceed the total radium MCL of 5.0 pCi/1. The results of these limited radioactive analyses indicates that waters of the Hickory aquifer within the study area are seriously contaminated with excessive leveboftotal radium. Excessively high total radium concentrations have been detected in Hickory waters in Mason and McCulloch Counties (Bluntzer, 1988). Also, other radioactive samples from wells in Llano, San Saba, and other parts of Mason and McCulloch Counties have detected excessively high radium concentrations in Hickory waters. Consequently, Evaluation of the Ground-Water Re!IOurces of the Paleozoic and Cretaceous Aquifers in the Hill Country off".entral Texas July 1992 85

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Ev .. luation of the Ground-Water Re!lOurce• of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas JuiJ' 1992 86 excessively high radium concentrations seem to be an inherent problem regionally with the use of Hickory waters for drinking purposes. The one alpha analyses (59 pCi/1) for the water from the Mid-Cambrian well in Gillespie County strongly indicates that the Mid-Cambrian aquifer may have a serious problem with radioactive waters. Additional analyses for total radium as well as alpha radiation are needed of the waters from this well and other Mid-Cambrian aquifer wells to confirm this apparent problem. The limited number of alpha analyses for Ellenburger-San Saba waters indicates that the aquifer has no apparent problem with radioactivity within the study area. Recent radioactive analyses of Ellenburger-San Saba waters from the San Saba member and the Gorman and Tanyard Formations (Table 1) in McCulloch and San Saba Counties north of the study area have provided similar results and the same conclusion. However, a recent analyses for alpha of the water from a well completed in the Honeycut Formation of the Ellenburger Group (Table 1) in southern Burnet County (just outside the study area) had an alpha concentration 10 pCi/1 greater than the MCL of 15 pCi/1. The one alpha analysis ( 4.4 pCi/1) for the water from the one Marble Falls well in Gillespie County indicates that the Marble Falls aquifer may not have a problem with radioactive waters. However, additional selected analyses for radioactivity of Marble Falls waters are needed to more accurately confirm this conclusion. The total radium analyses for Middle and Lower Trinity waters apparently indicate that these aquifers locally may have problems with excessive radiumconcentrations. TheonewellatFredericksburgwithwaterexcessively high in total radium (10.9 pCi/1) is understandable, since the well is completed in the hydrologically connected Middle Trinity and Hickory aquifers. The excessively high total radium concentrations detected in the Lower Trinity water at Comfort (6.0 pCi/l) and the Middle Trinity water at Ingram (5 .. 3 pCi/1) are not fully understood. Additional water samples for radioactive analyses are needed from these wells as well as other Lower and Middle Trinity aquifer wells to confirm if high radioactivity is a local and/ or regional problem with waters from the Trinity Group aquifers. Radon which is a strongly radioactive gas is a radioactive decay product of certain specific isotopes of radium. The radon-222 isotope is the radioactive decay product of radium-226. Cech and others, 1988 detected high concentrations ofradon-222 in ground waters from the Hickory aquifer in McCulloch County north of the study area. Water wells completed in aquifers having concentrations of radium are probably conveyors of radon gas to the land surface. Also, water pumped by such wells can deliver radon gas to dwellings and other enclosed structures where it can become concentrated and pose the greatest health risk. Radon at elevated levels poses greater health risks than any other constituent currently regulated by the Safe Drinking Water Act. However, a primary drinking water standard MCL for radon has not yet been determined. In the future when selected radioactive analyses are made in the study area, such analyses should attempt to :include the analyses for radon-222. Additional information on alpha radiation (gross alpha), radium, and radon as well as other radioactive constituents in water are provided in Appendix A.

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The most likely source for the excessive radium concentrations in Hickory waters may be from high concentrations of radioactive minerals which were derived from underlying Precambrian rocks and deposited in a specific bed or beds within the Hickory sandstone member of the Riley Formation (Table 1). These radioactive beds may be readily delineated in the boreholes of existing and future Hickory wells by the use of commercially available borehole geophysical logs. Mter the radioactive beds have been delineated, they can be sealed-off and prevented from supplying the radioactive water directly to the well bore. This method of controlling the production of radioactive ground water has been used in Gulf Coast aquifer of southeast Texas with some success. However, the use of this method on a large-capacity well for public supply may seriously reduce well specific capacity to such an extent that the well may not be capable of performing as a reliable, long-term water supply. Evaluation of the Ground-Watf'r Re!IOurces of the Paleozoic and Cretaceous Aquifen in the Hill Country of Central Texas July 1992 87

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Historically, ground-water pumpage from the various aquifers has been used mainly for public supply, rural domesti.::, irrigation and livestock watering purposes. As an example, in 1985 these combined uses amounted to about 18,613 acre-feet or about 99.3 percent of the 18,739 acre-feet of total estimated ground-water pumpage. Of the 18,613 acre-feet amount; 8,086 acre-feet was used for public supplies, 5,896 acre-feet was used for rural domestic water supplies, 2,390 acre-feet was used for irrigation, and 2,241 acre-feet was ust!d for livestock watering. The remaining 126 acre-feet which is less than one percent of the total pumpage was used for manufacturing and mining purposes. Of the 377 estimated large-capacitywellswhich were accounted for as having been used in 1985; 278 wells or 73.7 percent were used for public supply purposes, one well or about 0.3 percent was used for manufacturing purposes, and 98 wells or 26.0 percent were used for irrigation. The number of wells used for rural domestic water supplies, mining purposes and livestock watering are unknown. In 1985, about '7 ,203 acre-feet of ground water was pumped from the Trinity Group aquifers using about 321 large-capacity wells for public supply, manufacturing; and irrigation purposes. An unknown number of additional wells were used to pump about 6,760 acre-feet for rural domestic supplies (5,029 acre-feet), mining ( 105 acre-feet) and livestock watering ( 1,626 acre feet). The largest centers of ground-water pumpage for public supply from the Trinity Group aquifers in 1985 included Kerrville (872 acre-feet using 13 wells), Ingram (376 acre-feet using 4 wells), Wimberly (363 acre-feet using 5 wells), Boerne (336 acre-feet using 8 wells), Dripping Springs (294 acre-feet using 2 wells), Comfort (217 acre-feet using 5 wells) and Bandera (199 acre-feet using 3 wells). In 1985, Kerrville also used about 2,870 acrefeet of surface water from Quinlan Creek and the Guadalupe River, and Boerne also t;.sed about 451 acre-feet from a city lake on Cibolo Creek. Other centers of ground-water pumpage include the Canyon Lake area of Comal County where about 23 private water companies pumped about 1,068 acre-feet using about 60 wells, and the Wimberly area in Hays County where a private water company pumped about493 acre-feet using 3wells. In 1985, approximately 2,379 acre-feet of ground water from the Trinity Group aquifer was pumped for irrigation by approximately 68 wells in Bandera County (12 wells), Blanco County (6 wells), Gillespie County (24 wells), Kendall County (12 wells), and Kerr County (14 wells). The second most used aquifer is the Ellenburger-San Saba aquifer in Gillespie and Blanco Counties. In 1985, about 2,545 acre-feet of ground water was pumped using about 28largt!-capacitywells for public supply and irrigation An unknown number of additional wells were used to pump about 266 acre-feet for rural domestic supplies ( 141 acre-feet), mining ( 16 acre-feet) and livestock watering ( 109 acre-feet). The largest centers of ground-water pumpage f4:>r public supply in 1985 included Fredericksburg (1,828 acre-feet using 5 wells) and johnson City (152 acrefeet using 2 wells). In 1985,Johnson City supplemented their supply from the Ellenburger-San Saba aquifer with about 58 acre-feet of surface water from the Pedernales River. Approximately 526 acre-feet of ground water Evaluation of the Ground-Water Resources of the P..aleozoic and Cretaceous in the Hill Countr, of Central Texas July 1992 GROUND-WATER AV AII.ABILITY Utilization and Development of Gronnd Water 89

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of the Ground-Water ResCiurces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 90 was pumped in 1985 from the Ellenburger-San Saba aquifer for irrigation in Blanco County (6 wells) and Gillespie County (10 wells). The third most used aquifer is the Edwards Plateau aquifer in Bandera, Gillespie, and Kerr Counties. In 1985, only about 110 acre-feet of ground water was pumped using 4 large-capacity wells for public supply and irrigation purposes. An unknown number of additional wells were used to pump about 982 acre-feet for rural domestic supplies (586 acre-feet) and livestock watering ( 396 acre-feet). The only center of pumpage for public supply was one private water company well near Harper in Gillespie County which withdrew about 7 acre-feet of ground water in 1985. Approximately 103 acre-feet was pumped in 1985 from the Edwards Plateau aquifer by 3 irrigation wells in Gillespie County. The Hickory is the fourth most used aquifer in the study area. In 1985, about 614 acre-feet of ground water was pumped using 21 large-capacity wells fo:r public supply and irrigation purposes in Blanco and Gillespie Counties. An unknown number of additional Hickory wells were used to pump about 157 acre-feet for rural domestic supplies (93 acre-feet) and livestock watering ( 64 acre-feet). Approximately 203 acre-feet of Hickory water was pumped by Fredericksburg in 1985 using one well within the city and two wells north ofthe city in north-central Gillespie County. Part of the water from the well in the city is produced from the Middle Trinity aquifer (Hense II sand). Since waters from these wells have excessive concentrations of radium, the wells are used only to supplement the city's supply from the Ellen burger-San Saba aquifer during peak summertime demands. In 1985, about seven additional privately owned wells were used in the Fredericksburg area to pump about 29 acre-feet of Hickory water for public supply purposes. Approximately 382 acre-feet of Hickory water was pumped for irrigation purposes in Blanco County (2 wells) and Gillespie County (9 wells). Relatively small amounts of additional ground water are pumped from the Mid-Cambrian, Marble Falls and Precambrian aquifers in Blanco, Gillespie and Travis Counties. In 1985, approximately 51 acre-feet was pumped from the Mid-Cambrian aquifer for rural domestic supplies (25 acre-feet) and livestock watering (26 acre-feet). Approximately 29 acre-feet was pumped from the Marble Falls aquifer for public supply (6 acre-feet for a rural subdivision in Travis County), rural domestic supplies (12 acre-feet) and livestock watering ( 11 acre-feet). Approximately 22 acre-feet was pumped in 1985 from Precambrian aquifers for public supply (3 acre-feet in northern Gillespie County for Enchanted Rock State Park), rural domestic supplies ( 10 acre-feet) and livestock watering (9 acre-feet). The approximate ground-water pumpage (acre-feet) and the approximate number oflarge-capacitywells used in 1985 by use category, by aquifer are presented in Table 13. The estimated 1985 ground-water pumpage by county, by use category, by aquifer, and corresponding estimated number oflarg•e-capadtywells used in 1985 are provided in Appendix D. Figure 23 provides the locations of most of the large-capacity wells used in the study area, and graphs showing the annual amounts of ground-water and surfacewater used from 1955 through 1986 by 14 selected municipalities, water districlts and water supply corporations.

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Table 13.-Approximate Ground-Water Pumpage in Acre-Feet and Number of Wells Used in 1985 (A-F means acre-feet. U means number of wells uaed is unknown) Edwards Plateau Trinity Group Marble Falls Ellen burger-San Mid-Cam brian Hickory Precambrian Total Percent of I Aquifer Aquifers Aquifer Saba Aquifer Aquifer Aquifer Aquifer Totals I Pump-No. Pump-No. Pump-No. PumpNo. PumpNo. PumpNo. PumpNo. Pump-No. Pump-Used l l.atPgory agP Wt>lls agP Wt-lls agtWt>lls agtWt-lls agP agP WPllo; :tVP :tVP Wells a uP Wells I 0 --o-o(A-F) (A-F) (A-F) (A-F) (A-F) (A-F) (A-F) (A-F) (A-F) Major Public Supply --4,431 105 -1,980 7 203 3 -6,614 115 35.3 30.5 Other Public Supply 7 1 1,388 147 6 2 39 5 --29 7 3 1 1,472 163 7.8 43.2 Rural Domestic Suppiy 586 u 5,029 u 12 u 141 u 25 u 93 u iO u 5,896 u 31.5 -Manufacturing -5 1 ------5 1 <0.1 0.3 Power ---------Mining -105 u -16 u ---121 u 0.6 -Irrigation 103 3 1,379 68 --526 16 -382 11 -2,390 98 12.8 26.0 Livestock 396 u 1,626 u 11 u 109 u 26 u 64 u 9 u 2,241 u 12.0 -Total Pumpage 1,092 -! 15,963 321 29 2 2,811 28 51 u 771 21 22 1 18,739 377 100.0 100.0 and LargeCapacity Wells Used Percent of 5.8 1.1 74.5 85.1 0.2 0.5 15.0 7.4 0.3 -4.1 5.6 0.1 0.3 100.0 100.0 --Totals

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E1'aluation of the Ground-Water R :sources of the Palcowic and Cretaceous Aquifcn in the Hill Country of Central Texas July 1992 92 Estimated Ground Water Available for Future Development Based on evaluations of estimated historical base flow, estimated underflow of ground waters, and distribution of historical annual rainfall, the aquifers within the study area receive about 450,000 acre-feet of average annual natural recharge which equates to about 5 percent of the average annual rainfalJ of about 9.0 million acre-feet. Coupled with the relatively large but unknown amount of ground water in transit storage, it would seem apparent that this very large amount of ground water which is physically available on a perennial basis would be more than adequate to fulfill the expected watersupply needs for many decades without any problems. However, only a very small portion of this relatively large amount of ground water can be realistically recovered by wells on a sustained basis. This condition is due to the extremely low coefficients of transmissibility and storage of the aquifers; particularly those of the Trinity Group aquifers. This condition coupled with the inability or unwillingness of many of the ground-water users in the area to practice and use more prudent ground-water exploration and drilling techniques, proper well spacing, and proper well construction and/ or well development, causes extreme water-level declines within and near centers of ground-water withdrawals for public supply purposes. Throughout the study area, very significant, long-term net water-level declines have occurred historically within and near centers ofpumpage for public supply purposes. Evaluations of historical water-level declines, historical ground-water pumpage trends, and historical available drawdowns (amounts of artesian heads above the topoftheaquifer) indicate that future available drawdowns would be depleted by the year 2000 at Fredericksburg's Hickory Well No. 18, Bandera's Lower Trinity Well No. 4 and Kerrville's ' Lower Trinity Well No.4 (using the historical water-level decline trend and the historical pumpage trend before surface water was used at Kerrville). Similar depletion of available drawdown was determined for the St. Stephens School Lower Trinity Well in Travis County where a very small amount of pumpage has depleted available drawdown at a net rate of about 4 feet per year. Examinations oflong-term, historical, net water-level declines at and near Bandera, Dripping Springs, Comfort, and Boerne indicate much less rates of historical, net water-level declines, but a more widespread gradual depletion of water from storage in the Middle Trinity aquifer; particularly in eastern Kerr, western Kendall, and eastern Bandera Counties. If continued, this gradual depletion or mining ofMiddle Trinity aquifer storage will cause a decrease of aquifer transmissibility which in turn will cause well yields to severely decrease. As well yields decrease, more and more wells will be required to meet expected water needs. If such additional wells are not properly located and constructed, water levels and well yields will continue to decline at even more alarming rates. In addition, as storage is depleted in the Middle Trinity aquifer, waters with excessive sulfate contents in the evaporite beds of the overlying Upper Trinity aquifer may be induced to leak downward into the Middle Trinity aquifer and deteriorate groundwater quality.

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Considering water-level declines in and near areas of concentrated public supply and the potential downward leakage of poor quality water, a method was developed to estimate the sustained yield of the Trinity Group aquifers. Using hydrographs of historical water levels from observation wells in and near centers ofpumpage and the historical records of annual pumpage, an annual sustained yield "duty" was determined for an approximate specific area which was estimated to be influenced by pumpage from the Trinity Group aquifers. The duty (expressed in acre-feet per year per square mileaf/yr/mi2 ) was determined using an estimated average annual pumpage within an estimated specific area influenced by such pumpage during a selected period of years when hydrographs indicated an apparent stabilization of water levels. This method is not highly accurate 1) because the area of pumpage influence (mi2 ) had to be selected based on limited available data on distribution of pumpage and aquifer characteristics, and 2) because of the very limited of observation wells and limited water-level data available to provide meaningful hydrographs for determination of periods of apparent water-level stabilization within and near the area influenced by the pumpage. However, the available data (water-levels and pumpage) was considered to be sufficient to provide a reasonably accurate perspective on the annual sustained yield ofthe Trinity Group aquifers to prevent adverse long-term water-level declines and related adverse encroachment of poor quality water. Sufficient data was available to estimate sustained yield "duties" for the Trinity Group aquifers at and near Kenville, Bandera, Boerne, Comfort, and the St. Stephens School area ofTravis County. Using these results and other hydrogeological knowledge of the Trinity Group aquifers, estimated duties were distributed on an areal basis by county. The annual sustained ground-water yield (af/yr) of the Trinity Group was then calculated by multiplying the distributed estimated duties (af/yr /mi2 ) and the relevant areas (mF) where the aquifers were determined to occur within each county. The annual sustained yield "duties" determined for the Trinity Group aquifers were used to estimate annual sustained yield "duties" for the Edwards Plateau aquifer. Sufficient water-level and pumpage data were not available to use the "duty" method to estimate the annual sustained yields of the various Paleozoic aquifers. Instead, the average annual amounts of natural recharge previously determined for the various Paleozoic aquifers are accepted as reasonably accurate estimates of average annual sustained yields. The approximate annual sustained yields (acre-feet peryear-af/yr) for the Cretaceous and Paleozoic aquifers are provided in Table 14. The estimated total annual ground-water sustained yield of 46,000 acre-feet for the study area only amounts to about 10 percent of the area's estimated average annual natural recharge of 450,000 acre-feet. The 46,000 acre-feet annual sustained yields of the Cretaceous and Paleozoic aquifers is the approximate amount of ground water that can be recovered by wells without adversely effecting baseflow (ground-water discharge) to area eilluent streams, and without causing adverse water-level decllines and related encroachment of poor quality water; particularly in the Trinity Group aquifers. Evaluation of the Ground-Water Rc50urces of the Paleozoic and Cretaceous in the Hill Country of Central Texas July 1992 95

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t:"aluation of the Ground-Water Resources of the l'alcozoic and Cretaceous Aquifen in the II• II Country of Centra: Texas July 1992 96 Table 14.Approximate Annual Sustained Yields in Acre-Feet Per Year for the Paleozoic and Cretaceous Aquifen I!AIWai'CIS 1 nmty Marole u.enourger MJO 1 ouu IUlnuaa Plateau Group Falls -San Saba Cambrian Hickory Sustained County Aquifer Aquifen Aquifer Aquifer Aquifer Aquifer Yield (af/yr) (af/yr) (af/yr) (af/yr) (af/yr) (af/yr) (af/yr) Bandera Blanco Co mal Gillespie Hays Kendall Kerr Medina Travis Totals For Study Area 700 100 1,400 400 2,600 5,200 6,500 1,600 300 4,600 300 800 1,800 3,400 4,000 300 2,000 1,800 4,400 7,200 900 28,500 300 8,600 600 2,800 The results obtained from the use of the "duty" method to estimate the sustained yield of the Trinity Group aquifers admittedly could be somewhat inaccurate because of the limited amoun tofwater-level and pumpage data and information available for application of the method. At best, the resulting sustained yield of 28,500 acre-feet per year for the Trinity Group aquifers should be considered to be a gross approximation. Even if the annual sustained yield of the Trinity Group aquifers is 50 to 100 percent greater (which is very doubtful) additional water supplies need to be developed to meet long-term projected water demands expected in and adjacent to current centers of pumpage for public water supply purposes. Additional ground water for public supply purposes is available in the Trinity Group aquifers in remote areas which are considerable distances from the current centers of pumpage. In 1985, approximately 13,963 acre-feet of ground water was withdrawn by wells from the Trinity Group aquifers. This amount probably represents the average annual withdrawal by wells from the aquifers during the middle and late 1980s. If the average annual withdrawal from the aquifers was approximately 14,000 acre-feet, then approximately 14,500 acre-feet per year of additional ground water would be available in the remote areas away from current centers of pumpage. However, development of this remote additional available ground water for public supply purposes would entail great costs for additional lands, properly located, constructed and operated wells, additional water delivery facilities, and in some cases additional water storage facilities. Significantly large amounts of additional water for public supply purposes is physically available from the base flow and storm runoff of the area's streams; particularly the Pedernales, Guadalupe, Blanco 7,200 7,700 1,800 11,100 1,800 4,800 9,800 900 46,000

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and Medina Fivers. However, acquisition and development of such waters also will entail great costs, and in most cases contractual arrangements between water users and water suppliers (holders of surface-water rights). It is very apparent that conjunctive use of ground water and surface water on a regional scale is the proper means of meeting future public water supply needs. Such a regional program needs to be implemented in a timely manner through careful planning, appropriate coordination and arrangements between water users and water suppliers and the willingness of water users to pay the high costs for future adequate and safe public water supplies. Within the last 10 years conjunctive use of ground water and surface water has been practiced successfully by the public water supply systems at Kerrville, Boerne, and Johnson City. Similar conjunctive use programs need to be implemented at Bandera, Fredericksburg, Blanco, Comfort, Ingram, and urban areas acUacent to all of the above major communities, and in other portions of eastern Bandera County, northwestern Co mal County, northwestern Hays County, and southwestern Travis County. The best method or methods for artificial recharge of an aquifer should use proper amounts of water with appropriate quality, and recharge facilities that are capable of delivering waters in to the saturated thickness in a timely and efficient manner. Artificial recharge operations should be strategically located in an area or areas where the recharged waters can be effectively stored and subsequently recovered for beneficial uses (modified from Bluntzer, 1988). Artificial recharge by direct methods include injection by wells into and/or just above the zone of saturation or by spreading of water at the land surface above the zone of saturation with the use of special surface facilities and means such as pits, trenches, basins, stream channel modifications, flooding, irrigation and ditch and furrow (O'Hare and others, 1986). The spreading method at the land surface assumes that waters being applied will infiltrate through the unsaturated zone above the aquifer and move downward and replenish the zone of saturation. Therefore, the spreading method can only be effectively used in areas where the aquifer is unde1 water-table (unconfined) conditions. Artificial recharge by wells can be used in areas where aquifers are under water-table (unconfined) conditions or under artesian (confined) conditions. If artificial recharge of the Cretaceous and Paleozoic aquifers is considered, a detailed data collection program and a detailed hydrogeological study of the aquifer and the area to be recharged should be completed to determine: 1) the geological conditions (stratigraphy and structure) related to the occurrence of all water-bearing and non-water-bearing units; 2) the amount, distribution and extent of saturated thickness and the hydraulic properties of the aquifer; 3) the amount, distribution and extent of any measurable dewatered portion of the aquifer, if all orpartofsuch aquifer is underwatertable (unconfined) conditions; 4) the natural ground-water recharge, movement and discharge of the aquifer, and the ground-water and surfacewater relationships in and adjacent to the area; 5) the amounts of ground water historically and currently withdrawn from alllarge-capacitywells and the location and aquifer designation of each well; 6) the water quality characteristics of all ground waters, and the identification of existing and potential water-quality problems; 7) the approximate amount, water quality Evaluation of the Ground-Water Resources of the P-aleozoic and Cretaceous Aquifers in the Hill ('.ountry of Central Texas July 1992 Artificial Recharge of Growtd Water 97

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E\"dluation of the Ground-Water R( !Duree! of the l'aleozoic and Cretaceou! Aquifen in the Hill Country of Central Texa! July 1992 98 characteristics and existing and potential water-quality problems of available source water or waters intended for artificial recharge of the aquifer; 8) if the quality of the source water or waters is compatible with the water quality of the aquifer, and is suitable for recharge operations, aquifer storage and later recovery for beneficial uses; 9) the most suitable method for artificial recharge of the aquifer; and 1 0) if water rechargers and/ or users will physically and economically benefit from artificial recharge operations. In Texas, ground-water use is an inherent property right and landowner's may withdraw as much ground water as physically possible as long as the water is used for beneficial purposes and is not wasted. "'When water is artificially recharged into an aquifer, such water physically becomes ground water, and consequently becomes the property of all landowners who physically have access to such water and are capable and willing to recover such water for beneficial uses. Therefore, the lateral extent of the aquifer that artificial recharge will enhance needs to be determined, so that the landowner conducting the recharge-recovery operations will be the sole or at least the primary beneficiary on some economical basis. Otherwise, special arrangements between all landowners who would physically and economically benefit from such recharge-recovery operations would need to be made on a reasonably equitable basis. An artificial recharge study for the Hickory Underground Water Conservation District No. 1 in the Katemcy Creek basin of northern Mason and southern McCulloch Counties (Bluntzer, 1988) recommended that surface-water runoff be retained in small reservoirs and artificially recharged to the Hickory aquifer by wells; either through dual purpose recharge-recovery wells or through wells specifically constructed for recharge. The use of wells as the recharge method would assure that artificial recharge operations could be more readily controlled, and would allow the recharged water to be more efficiently placed into aquifer storage for beneficial recovery and use without significant loss or escape. The use of spreading methods for artificial recharge of the Hickory aquifer were determined to be undesirable, because there were no reasonable assurances that most of the recharged waters would not be lost or not escape from the area where the waters could be later recovered from aquifer storage for beneficial use. However, the study recommended that artificial recharge by wells be tested before funds were expended for the construction of an expensive surface-water retention structure. Even though the study concluded that artificial recharge could be accomplished physically, the District wisely decided that artificial recharge would not be economically feasible, because one very costly retention structure only would provide enough artificially recharged water for a very limited number of water users (irrigators) within a relatively small. portion of the total area that needed to be benefited by artificial recharge. A test to demonstrate the physical feasibility of artificial recharge was made in March 1955 by the U.S. Geological Survey at Kerrville by using City \Vell No.5 as the injection (recharge) well and City Well Nos. 4 and 7 as water level monitoringwells. According to Reeves ( 1969), the following information and conclusions resulted from this artificial recharge test of the Lower Trinity aquifer. 1) Water-level measurements in the injection well (City \Vell No.5) indicated a rise in water level of about 25 feet due to the injection of 400 gpm for 24 hours. 2) The theoretical rise in water level at the injection well using an injection rate of 1,000 gpm would be about 62.5 feet for one day or 8'7 .5 feet for 100 days. The actual rise may be somewhat more because of turbulence and frictional losses in and around the well. 3) It was

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concluded that water could be injected at a rate of at least I ,000 gpm. 4) The recharge water would probably require treatment to prevent clogging of recharge wells and the aquifer. 5) The Guadalupe River is the obvious source of water for artificial recharge purposes. 6) Additional studies should be made to determine the economic feasibility of using treated Guadalupe River water for artificial recharge of the Lower Trinity aquifer at Kerrville. Guyton ( 1973) addressed artificial recharge at Kerrville and indicated the following very important points and 1) Sinceitis usually much more difficult to inject (recharge) water into a well than it is to produce the water from the well by pumping, each specific artificial recharge project is a new experiment in itself. 2) Theoretical mathematical computations are available that :readily show that artificial recharge is simply the reverse of pumping. However, such things as bacteria, suspended matter, corrosion products, and entrained air introduced with recharge waters can readily clog recharge wells. Such things do not adversely affect producing wells. 3) The chemical quality ofthe recharge water and the chemical quality of the water in the aquifer should be compatible, so that the recharge well and the aquifer are not: clogged with undesirable chemical deposits. Also clogging of the aquifer is possible due to the swelling of clays in the aquifer caused by the chemical character of the recharge water. 4) Even though the U.S. Geological Survey's artificial recharge test of relatively short duration at Kerrville in 19fl5 was reported to be successful, a much longer test of several months using surplus water from the Guadalupe River would be more appropriate to determine the practicality of artificial recharge. Such a longer test would determine if the potential problems described in items 2 and 3 above would cause artificial recharge to be unfeasible. 5) Because of the confined conditions of the Lower Trinity aquifer and the variable seasonal demands for a reliable water supply, it would not be advantageous to practice artificial recharge at Kerrville, unless sufficient amounts of acceptable quality recharge water are available during reasonable and timely parts of every year. The Upper Guadalupe River Authority which provides a large part of the City of Kerrville's water supply currently is conducting an artificial recharge study in the Kerrville area. The study will be conducted in three phases to determine the physical and economical feasibility for artificial recharge of the Lower Trinity aquifer with surplus treated water from the Guadalupe River during ''wet" months and then recovering the recharged waters during "dry" months to meet Kerrville's peak water demands. This concept is intended to allow the Authority to use dual purpose wells to meet increasing pea.k water demands without immediate expansion of the Authority's water-treatment facilities. If successful, this aquifer storage and recovery (ASR) projectwouldallowmoreeconomical useoftheAuthority's current and futurewater-treatmentfacilities and at the same time physically enhance the public water supply for Kerrville (CH2M Hill, 1988). To date, phase one and a portion of phase two of the project have been completed. This part of the project determined the hydrogeology of the Lower Trinity aquifer at the proposed ASR site. The remaining part of the second phase of the project began in 1990 and consists of a long-term testing program on a prototype ASR well. If ASR is determined to be physically and economically feasible at the proposed ASR site, phase three of the project will establish, operate, and maintain an ASR well field. Five such ASR facilities have been successfully established and operated in Florida since 1983, New Jersey since 1968, and California since 1978 (CH2M Hill, 1988 and 1989). Evaluation of the Ground-Water Rewurces of the Paleozoic and Cretaceous Aquifers in the Hill Country ofC"..cntral Texas July 1992 99

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b.tluation of the GrmmdWater Resources of the Palco1.oic and Cretaceous Aquifer; in the Hill Country of Central Texas July 1992 100 If the ASR project at Kerrville proves to be successful, similar projects should be considered for the enhancement of public water supplies at Bandera, Comfort, Boerne and perhaps other public water supply systems in the study area and other parts of the State. However, such artificial recha1 ge projects will not be physically and economically feasible unless a sufficient supply of suitable quality surface water is available on a timely basis for treatment, recharge and recovery for beneficial use, and unless the entity conducting the recharge-recovery operations will be the sole or at least the primary beneficiary.

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In 1985, the population of the study area was concentrated mostly in and adjacent to the incorporated cities and towns; namely Kerrville, Fredericksburg, Boerne, West Lake Hills, Ingram, Lakeway, Dripping Springs, Blanco, Bandera,Johnson City, Wood creek, Bee Cave and Briarcliff. In addition, significant, unincorporated population centers included the communities of Wimberley, Comfort, Hunt, Center Point, Harper, and Stonewall. In 1985, approximately 38 percent of the population of 125,924 resided in incorporated and unincorporated communities. Also, significant concentrations of urban type population reside in rural residential subdivisions adjacent to these incorporated and unincorporated communities and in and adjacent to the Interstate Highway 10 corridor in Kerr and Kendall Counties and northwest of the Interstate Highway 35 corridor in Comal County (near Canyon Lake), Hays County (near WimberleyandDrippingSprings) andTravisCounty (nearLakeTravisand the U.S. Highway 290 West and State Highway 71 West corridors). From 1980 to 1985 the historical population increased from 98,204 to 125,924 which is a 28 percent increase in population for the five year period or an increase of about 5.6 percent per year (%/yr.). During the same period, population increases occurred within the study area with a 48 percent (9.6%/yr.) increase in Travis County; a 42 percent (8.4%/yr.) increase in Comal County, a 40 percent (8.0%/yr.) increase in Hays County, a 32 percent (6.4%/yr.) increase in Kendall County, a 26 percent (5.2 %/yr.) increase in Bandera County, a 17 percent (3.4 %/yr.) increase in Kerr County, a 14 percent (2.8%/yr.) increase in Gillespie County, and a 14 percent (2.8%/yr.) increase in Blanco County. The only area which had a decease in population from 1980 to 1985 was northern Medina County where there was a slight decrease of less than one (1) percent. Similar population growth is expected to continue through the year 201 0; especially in those portions of Hays, Comal and Travis Counties within the study area and Blanco, Bandera, Kendall and Kerr Counties, all of which are within the study area. From 1985 through 2010, the population is expected to increase from 125,924 to 219,874 which is a 75 percent increase for the 25year period or an increase of3.0 percent per year. For the 25yearperiod, population increases are expected to occur with the following projected increases: 134 percent (5.4%/yr) in Hays County, 108 percent (4.3%/yr.) in Comal County, 97 percent (3.9%/yr.) in Blanco County, 87 percent (2.5%/yr.) in Travis County, 63 percent (2.5%/yr.) in Bandera County, 62 percent (2.5%/vr.) in Kendall and Kerr Counties, 47 percent ( 1.9%/yr.) in Gillespie County and 24 percent (1.0%/yr.) in Medina County. Such population growth is expected to be concentrated in and adjacent to such communities as Kerrville, Fredericksburg, Boerne, West Lake Hills, Ingram, Ev-.lluation of the Ground-Water Resources of the Paleozoic and Cretaceous in the Hill Country of Central Texas July 1992 IDSTORICAL AND PROJECTED POPUlATION, IDSTORICAL WATER USE AND PROJECTED WATER DEMANDS Historical and Projected Population 101

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Ev.1luation of the Ground-Water Rescurces of the Paleozoic and CretaceouJ Aquifers in the Hill Country of Central Texas July 1992 Historical Water Use 102 Lakeway, Dripping Springs, Blanco, Bandera, Johnson City, Woodcreek, Bee Cave, Briarcliff, Wimberley, Comfort, Hunt, Center Point, Harper and Stonewall. Table 15 presents the 1980 and 1985 historical population and the 1990, 2000, and 2010 projected population by county and selected major cities. The 1980 and 1985 population figures were determined from U. S. Bureau of Census statistics and information. Population projections ( 1990-201 0) were estimated by extending U. S. Bureau of Census statistics according to growth rates used in the 1988 Texas Water Development Board Revised Data Series population projection methodology. The "County Other" population as indicated in Table 15 includes specified incorporated and unincorporated communities and all rural population. The population figures given are for the entire counties of Bandera, Blanco, Gillespie, Kendall and Kerr, and only those parts of Comal, Hays, Medina and Travis Counties within the study area (Figure 1). The total amount of water used in 1985 was about 30,430 acre-feet with 18,739 acre-feet or 61.6 percent from ground-water sources and 11,961 acrefeet or 38.4 percent from surface-water sources. In 1980, the total amount of water used was about 25,035 acre-feet with 1 7,828 acre-feet or 71.2 percent from ground-water sources and 7,207 acre-feet or 28.8 percent from surfacewater sources. The 1985 total water use of30,430 acre-feet was 21.5 percent greater than the 1980 water use, and was the result of increases in water used for public supply and rural domestic supply purposes. From 1980 to 1985, water used for public and rural domestic water supplies increased from 15,964 acre-feet to 22,872 acre-feet which was a 43.3 percent increase. Table 16 provides the estimated amounts of water used in 1980 and 1985 by water use categories and by sources (ground water and surface water). The estimated water used in 1980 and 1985 by county is provided in Appendix E. The approximate 1980 and 1985waterusewhich is provided in Table 16 and Appendix E was compiled as documented in Texas \Vater Development Board, 1988. Much of the public supply water use was obtained from the amounts reported to the Board by public water systems (cities, towns, water supply corporations, water districts, private water companies, etc.). Public water use not reported to the Board and rural domestic water use was computed using appropriate population and average per capita water use. Livestoclk water use was computed based on the rural geographical area (square miles) apportioned to county total livestock use. All other water uses were compiled based on site-specific computed use. Figure 2.3 provides graphs showing the historical annual water use through 1986 for 14 public water supply systems. As indicated, 10 of these systems historically have used ground water only, and include Bandera, Bandera Fresh \Vater Supply District No. 1, Medina Water Supply Corporation, Ingram, Kendall County Water Control and Improvement District No. 1 (Comfort), Fredericksburg, Dripping Springs Water Supply Corporation, Wimberley Water Supply Corporation, Haskin Water Supply, Inc., and Bulverde Hills Water System. The public water systems at Kerrville,Johnson City and Boerne historically have used ground water and surface water. Blanco which has not developed a reliable ground-water supply uses only surface water from the Blanco River.

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Evaluation of the Ground-Water Resources of the Paleo7oic and Cretaceous in the Hill Country of(.
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!.valuation of the Ground-Water l<.e10urces of the Paleozoic and Cretaceous Aquifers in the Hill CountryofCentral Texas July 1992 Table 15.-HistoricaJ Population in 1980 and 1985 and Projected Population in the Years 1990, 2000 and 2010 (cont'dJ County /City /Other 1980 1985 1990 2000 2010 Kendall County Boerne 3,229 4,685 4,434 5,139 5,910 Comfort 1,226 1,533 1,636 1,965 2,167 County Other 6.180 7.812 10.015 12.701 14.699 County Totals 10,635 14,030 16,085 19,805 22,776 Note: The histor.ical and projected population given for the unincorporated community of Comfort inclucks all persons estimated to be within the service area of the Kendall County Water Control and Improvement District No. 1. "C.ounty Other" inclucks population in the incorporated portion of Fair Oaks &nch in the county, the unincorporated communities of Bergheim, Kendalia, Lindendale, Sisterdale, Waring and Welfare, numerous rural residential subdivisions and the remaining rural area of the County. Kerr County KeriVille 15,276 18,024 21,619 26,966 31,147 Ingram 1,820 2,465 2,630 3,159 3,560 CountyOther 11.684 13.097 13.571 17.030 19.760 County Totals 28,780 33,586 37,820 47,155 54,467 Note: The historical and projected population given for the incorporated community of Ingram includes all persons estimated to be within the service area of the Ingram Water Supply system. "County Other" inclucks population in the unincorporated communities of C-amp Verde, Center Point, Hunt and Mountain Home, numerous rural resickntial and the remaining rural area of the county. Medina County County Other 627 625 624 685 773 Note: "County Other" includes population in the unincorporated community of Mico, rural residential subdivisions and the remaining rural area of the county. Travis County Lakeway 2,758 5,566 7,414 9,875 10,892 West Lake Hills 2,166 3,492 4,650 6,564 8,079 County Other 25.787 25.884 36.476 46.162 County Totals 23,544 34,845 37,948 52,915 65,133 Note: The historica,l and projected population given for Lakeway includes all persons estimated to be within the service area of the Lakeway Municipal Utility District. "County Other" includes population in the incorporated communitie;; of Bee Cave and Briarcliff, numerous rural residential subdivision and the remaining rural area of the county. Total Population of Study Area 104 98,204 125,924 140,970 183,990 219,874

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Ev-.aluation of the Ground-Water Resources of the P..aleozoic and Cretaceous in the Hill Country of .cntral Texas July 1992 Table 16.-Approximate Water Used in 1980 and 1985 Approximate Approximate 1980 Water Use in Acre-Fee 1985 Water use in Acre-Feet Ground Surface Total Ground Surface Total Water Use Category Water Water Use Water Water Use Major Public Supply 5,794 2,346 8,140 4,375 5,555 9,930 Other Public Supply 1,874 943 2,817 3,246 3,440 6,686 Subtotal Public Supply 7,668 3,289 10,957 7,621 8,995 16,616 Rural Domestic Supply 5,007 -0-5,077 6,203 53 6,256 Subtotal Drinking Water Use 12,675 3,289 15,964 13,824 9,048 22,872 Manufacturing 536 84 620 163 123 286 Power -0--0-0--0-0--0Mining -0--0--0121 -0121 Subtotal Industrial Water Use 536 84 620 284 123 407 Irrigation 1,778 2,613 4,391 2,390 1,421 3,811 Livestock 2,839 1,221 4,060 2,241 1,099 3,340 Subtotal Agricultul'al Water Use 4,617 3,834 8,451 4,631 2,520 7,151 Total Water Use 17,828 7,207 25,035 18,739 11,691 30,430 105

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Ev-.1luation of the Ground-Wat< r of the Palcowic and Crelaceom Aquifers in the Hill Country of Central Texas July 1992 Table 17. Approxitmate Water Used in 1980 and 1985 by Selected Major Public Water Systems County, Water System & Supply Bandera, City of Bandera From Ground-Water Supply From Surface-Water Supply Total Water Used Blanco, City of Blanco Approximate Water Use in Acre-Feet 1980 1985 190 -0190 170 -0170 Source of Supply Trinity Group Aquifer None From Ground-Water Supply -0--0None From Surface-Water Supply 239 226 Blanco River Total Water Used 239 226 Note: The Cil) of Blanco currently has a surface-water permit for diversion of 600 acrefeet per year from the Blanco River. Blanco, City of Johnson City From Ground-Water Supply From Surface-Water Supply Total Water Used 41 147 188 131 51 182 (See Note Below) Pedernales River Note: The Cil) of johnson City has a well Jield which produces ground water from the Ellenburger-San Saba aquifer. Also, tht city currently has a surface-water permit for diversion of 200 ncrefeet per year from the Pedernales River. Gillespie, City of From Supply From Surface-Water Supply Total Water Used 1,325 -01,325 1,606 -01,606 (See Note Below) None Note: The Cit) of Fredericksburg has well fields which produce ground water from the Ellenburger-San Saba aquifer, Hickory aquifer and Middle Trinity aquifer (llensell sand). Hays, Dripping Springs WSC From Ground-Water Supply 125 294 From Surface-Water Supply -0--0Total Water Used 125 294 Trinity Group Aquifer None Note: The water use for the Dripping Springs Water Supply Corporation (WSC) includes water used by residence within the inc01porated community of Dripping Springs and by residence adjacent to the community within the service area of the WSC. Hays, Wimberley VISC From Ground-Water Supply 263 363 From Surface-Water Supply -2:. -0Total Water Used 263 363 Trinity Group Aquifer None Note: The water use for the Wimberley Water Supply Corporation (WSC) includes water used by residence area of the WSC. Kendall, City of Boerne From Ground-Water Supply From Surface-Water Supply Total Water Used 233 381 614 326 451 777 Trinity Group Aquifer Cibolo Creek Note: The City of Boerne currently has a permit for diversion of 833 acrefeet per year from a city lake on Cibolo Creek. --------------------------------contmue 106

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Evaluation of the Ground-Water Resources of the P.olleozoic and Cretaceous A9uifen in the Hill Country of Central Texas July 1992 Table 17 .Approximate Water Used in 1980 and 1985 by Selected Major Public Water Systems (cont'd.) County, Water System & Supply Kendall, Kendall Co. WCID No. I From Ground-,Vater Supply From Surface-Water Supply Total Water Approximate Water Use in Acre-Feet 1980 1985 146 _.::Q: 146 217 ...=!t: 217 Source of Supply Trinity Group Aquifer None Note:The water use for the Kendall County Water Control and Improvement District (WCJD) No. 1 includes water used by residnce within and adjacent to the unincorporated community of Comfort. Kerr, City of Kerrville From Ground-,Vater Supply 3,178 850 From Surface-Vvater Supply 96 2.844 Total Water Used 3,274 3,694 Trinity Group Aquifer Guadalupe River Note: The City of Kerrville currently has a for diversion of 15 5acrefeet per year from the Guadalupe River and Qy,inlan Cre.'!k. Kerrville's major surface--water supply is treated Guadalupe River water obtained from the Upper Guadalupe River Authority. Such supp(y currently is limited by contract to 3, 603 acre-feet per year. Kerr, City of Ingram From Ground-'Nater Supply From Surface-,Nater Supply Total Water Used 293 -0293 376 -0376 Trinity Group Aquifer None Note: The water use for the City of Ingram includes water used by residence within and adjacent to the city within the service area cfthe Ingram Water Supply which is a private water company. Travis, Lakeway MUD From Ground-'Nater Supply -0--0None From Surface-\Vater Supply 767 L22l. Lake Travis Total Water Used 767 1,251 Note: The City Lakeway and some adjacent water users are supplied surface water by the Lakeway Municipal Utility Disi'rict (MUD) which purchases the water from the Lower Colorado River Authority. Such supply currently i.s limited by contract to 1,228 acrefeet per year. Travis, City of'Nest Lake Hills From Ground-'Water Supply -042 From Surface-,Vater Supply 716 732 Total \Vater 716 774 Trinity Group Aquifer Lake Austin Note:The City c{West Lake Hills obtains its main water supply from Lake Austin through the Travis County M1ater Control and Improvement District No. 10 which purchases treated water from the City of Austin. Ground water from the Trinity Croup aquifers is supplied to small portions of the city by wells at Ridgewood Village, the G & J Water District and the Eanes Independent School District. 107

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halualion of the Ground-Water Rewurces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Table 18. Water Demands in the Years 1990, 2000, and 2010 Water Demand Category Major Public Supply Other Public Supply Subtotal Public Supply Rural Supply Subtotal Drinking Water Demand Manufacturing Power Mining Subtotal Industrial Water Demand Irrigation Livestock Subtotal Agricultural Water Demand Total Water Demand Projected Water Demand in Acre-Feet (Texas Water Development Board, 1988) 1990 2000 2010 I5,366 I9,580 22,404 8,I44 II,076 I3,734 23,5IO 30,656 36,I38 6,859 9,328 11,242 30,369 39,984 47,380 828 I ,II2 1,416 -0--0--024 48 36 852 I,I60 I,452 3,4I3 3,466 3,509 4,700 5,349 5,349 8,113 8,815 8,858 39,334 49,959 57,690 Table 19. Projected Water Demands in the Years 1990, 2000, and 2010 for the Selected Major Public Water Systems County, Water System Public Supply Bandera, City of Bandera Blanco, City of Blanco Blanco, City ofjohnson City Gillespie, Cit1 of Fredericksburg Hays, Dripping Springs WSC Hays, Wimberly WSC Kendall, City of Boerne Kendall County WCID #I (Comfort) Kerr, City of Kerrville Kerr, City of 1 ngram Travis, Lake\\ ay MUD Travis, City West Lake Hills Total 108 Projected Water Demand in Acre-Feet (Texas Water Development Board, 1988) 1990 2000 2010 15,366 19,580 22,404 573 848 981 455 623 784 348 475 597 2,234 2,731 3,044 363 514 666 470 622 774 I,227 1,445 1,662 227 259 270 5,8I2 7,400 8,548 411 468 499 2,008 2,537 2,648 I,238 I,658 1,931 15,366 19,580 22,404

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Table 17 provides the approximate amounts and the sources of water used in 1980 and 1985 by 12 selected maJor public water supply systems. In 1980, numerous smaller public water supply systems which mainly consist of private water <:ompanies, water districts, and water supply corporations used about 2,817 acre-feet of which 1,874 acre-feet was ground water and 943 acre-feet was surface water. Approximately 92 of these smaller public water systems supplied the 1,874 acre-feet of ground water. In 1980, most of these smaller systems using ground water were located in Comal County (41), Kerr County (25), and Kendall County (8). The 943 acre-feet of surface water used in 1980 was supplied by the Cir; of Austin and the Lower Colorado River Authority to such smaller systems in Travis County. In 1985, such numerous, smaller public water supply systems used about 6,686 acre-feet of which 3,246 acre-feet was ground water and 3,440 acrefeet was surface water. Approximately 120 of these smaller systems supplied the 3,246 acre-feet of ground water. In 1985, most of these smaller systems using ground water were located in Comal County (40), Kerr County (34), Kendall County (10) and Travis County (14). The 3,440 acre-feet of surface water used in 1985 was supplied by the Bexar-Medina-Atascosa Counties WCID Ko. 1 to a rural residential subdivision in Bandera County (18 acrefeet), and the City of Austin and the Lower Colorado River Authority through local water districts in Travis County (3,422 acre-feet). In 1980 and 1985, most of the water used for rural domestic supply purposes was estimated to::> have been provided by numerous small-capacity wells completed in the Cretaceous and Paleozoic aquifers. Some of the water used for rural domestic supplies was provided by some of the public water systems. From 1980 to 1985, water used for rural domestic supplies increased from about 5,007 acre-feet to about 6,256 acre-feet; particularly in Travis, Kenda.ll, Gillespie, Bandera and Hays Counties. All of the water used in 1980 ;:Or rural domestic supplies was from ground water. Approximately acre-feet was supplied by wells, while 110 acre-feet was ground water supplied by the City of Fredericksburg to rural residences adjacent to the city. Of the 6,256 acre-feet used in 1985 for rural domestic supplies, 6,203 acrefeet was from ground water and 53 acre-feet was from surface water. Of the 6,203 acre-feet of ground water used, approximately 5,854 acre-feet was supplied by rural domestic wells and approximately 349 acre-feet was supplied to rural residence adjacent to the City of Bandera (29 acre-feet), the City ofjohnson City (21 acre-feet), the City ofFredericksburg (269 acrefeet), the City of Boerne ( 10 acre-feet), and the City of Kerrville (20 acre feet). The 53 acre-feet of surface water used for rural domestic supplies in 1985 was estimated to have been supplied by the City of johnson City (22 acre-feet), the City of Blanco (11 acre-feet), and the City of Kerrville (20 acre-feet). Water use for manufacturing purposes was estimated to be about 620 acrefeet in 1980 and about 286 acre-feet in 1985. In 1980, about 536 acre-feet was supplied from ground water, while 84 acre-feet was supplied from surface water. Of the 536 acre-feet of ground water, 505 acre-feet were supplied by the City of Kerrville and 12 acre-feet were self-supplied by two manufacturing firms; one using 8 acre-feet in Bandera County and one using 4 acre-feet in Kendall County. Of the 84 acre-feet of surface water used in 1980 for manufacturing purposes, one acre-foot was supplied by the City of Johnson City and 83 acre-feet were supplied from local sources (river, creek, pit, etc.) in Gillespie and Kendall Counties. Evaluation of the Ground-Water Rc!IOurces of the Paleozoic and Cretaceous Aquifers in the Hill C.ountryofC.cntral Texas July 1992 109

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Evaluation of the Ground-\\'atcr Resourc•!S of the Paleozoic and Cretaceous Aquifen in the Hill Country of Central Texas July 1992 110 In 1985, for manufacturing purposes, about 163 acre-feet were supplied from ground water, while 123 acre-feet were supplied from surface water. Of the 163 acre-feet of ground water, 156 acre-feet were supplied by the City of Fredericksburg, 2 acre-feet were supplied by the City of Kerrville and 5 aae-feet were self-supplied by a manufacturing firm in Kendall County. Of the 123 acre-feet of surface water used in 1985, one acre-foot was supplied by the City of johnson City, 5 acre-feet were supplied by the City Kerrville and 117 acre-feet were supplied from local sources in Gillespie County. Approximately 121 acre-feet of ground water was used in 1985 for mining purposes in Bandera County (24 acre-feet), Gillespie County ( 16 acre-feet), and Kerr County (81 acre-feet). There was no water use for mining purposes in 1980, and none used in 1980 and 1985 for steam-electric power generation purposes. In 1984, approximately 2,650 acres were irrigated (Texas Water Development Board, 1989d). The approximate acreage irrigated by county was as tollows: 213 acres in Bandera County, 233 acres in Blanco County, 1,201 acres in Gillespie County, 63 acres in Hays County, 114 acres in Kendall County and 826 acres in Kerr County. The portions ofComal, Medina and Travis counties within the study area were determined not to have any irrigated acreage in 1984. The types of crops irrigated in 1984 included crops for raising of livestock ( 1,680 acres of grasses, hay, and forage); orchards ( 517 acres); pecans (20 1 acres); grains ( 130 acres); vineyards ( 80 acres); and vegetables ( 42 acres). Irrigated acreage in 1984 was somewhat scattered and occurred mostly where there are developed soils in the bottom lands of the Pedernales, Blanco, Guadalupe and Medina Rivers and their tributaries. However, some irrigated lands are found in upland portions of Gillespie and Blanco Counties where soils have developed on the outcrops of the Hickory sandstone and Hensell sand. [n 1980, irrigationwaterusewasabout4,391 acre-feetwith about 1,778acrefeet from ground water and 2,613 acre-feet from surface water. Ninety-two percent of the irrigation water was used in Gillespie County (1,680 acre feet), Kerr County (1,284 acre-feet), Bandera County (538 acre-feet) and, Kendall County (536 acre-feet). In 1985, irrigation water use was about 3,811 acre-feet with about 2,390 acre-feet from ground water and 1,421 acre-feet from surface water. In 1985, about 80 percent of the irrigation water was used in Gillespie County ( 1,859 acre-feet) and Kerr County ( 1 ,200 acre-feet). Since the study area has large amounts ofland used for grazing, there is a very significant water need for raising livestock. Water used for raising livestock is supplied by numerous wells and local sources of surface water in stock tanks and streams. In 1980, approximately 4,060 acre-feet of water was used for livestock watering. Approximately 2,839 acre-feet of this water was provided by wells and 1,221 acre-feet was provided by local surfacewater sources. In 1985, water used for raising livestock was about 3,340 acrefeet with 2,241 acre-feet from ground water and 1,099 acre-feet from surface water. Approximately 84 percent of the water used for livestock watering purposes is used in Gillespie, Blanco, Kendall, Kerr, Hays and Bandera Counties.

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The total annual water requirement for the study area is expected to increase by about 90 percent from 1985 through the year 2010. The expected increase is about 130 percent from 1980 through the year 2010. These very large expected increases primarily are due to the large projected population increases previously described. Such population growth will need adequate supplies of suitable quality water for drinking and other household purposes. Water needed for such purposes is expected to increase about 107 percent from 1985 through 2010and about 196percent from 1980 through 2010. Water needed for public water supply systems is expected to increase about 117 percent from 1985 through 2010 and about 230 percent from 1980 through 2010. Water needed for rural domestic supply purposes is expected to increase about 80 percent from 1985 through 2010 and about 125 percent from 1980 through 2010. Slightly larger i r1creases in water uses for manufacturing needs is expected to occur through the year 2010 from about 828 acre-feet in 1990 to about 1,416 acre-feet in 2010. Annual amounts of water needed for mining are expected to be about 24 to 48 acre-feet per year through the year 2010. Future irrigation water needs are expected to be about 3,413 to 3,509 acrefeet per year during the 1990 through 2010 period. Water for livestock raising is expected to increase about 60 percent from 1985 through the year 2000 and about14 percent from 1980 through 2000, then level-off at about 5,349 acre-feet per year from 2000 through 2010. Table 18 provides the projected water demands for the years 1990,2000, and 2010 by water demand category. The projected water demands for 1990, 2000 and 2010 by county are provided in Appendix F. The expected water demands for public supply and rural domestic supply are based on population projections and projected high per capita water use with conservation used in the 1988 Texas Water Development Board Revised Data Series. All other projected water demands are based on high series (preliminary draft) projected demands and the apportioned share of total county demands. High series projected water demands are the demands which are likely to occur under a "dry year" condition. Almost 40 percent of the total high series projected water needs is expected to be required by the 12 major public water supply systems provided in Table 17. Table 19 provides the expected water needs for each of these 12 systems for the years 1990, 2000, and 2010. The large historical population growth and related historical increases in water used for public supply purposes experienced from 1980 to 1985 and the large projected population growth and related projected public water supply demands expected through the year 2010, strongly indicate a very substantial need for additional and safe drinking water supplies. On a practical basis, sufficient amounts of acceptable quality ground water are not expected to be physically and/ or economically available for development to fulfill all or in some cases even part of these large expected additional drinking water demands through the year 2010. This deficiency of acceptable quality ground-water supplies for drinking purposes is expected to be most acute for public water supply systems where the Trinity Group aquifers are Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Projected Water Demands 111

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Evaluation of the Ground-Water ReS<)IIrces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 112 the only available source of ground water. Such deficiency of ground water from the Trinity Group aquifers is expected to occur in urbanized areas in parts of Bandera, Blanco, Comal, Hays, Kendall, Kerr, and Travis Counties. Such areas of water supply deficiency will need to acquire additional ground water in remote areas away from current centers of pumpage or surfacewater supplies either through permit or purchase to help meet the large expected water needs through the year 2010.

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Before 1956, apparently all of the existing major public water systems depended entirely on ground water for their water supply. This condition is illustrated by examination of the water use graphs shown in Figure 23. The graph for Blanco indicates that it was the first major public water system to practice conjunctive use of ground water and surface water in 1956. Other major public water systems which initiated such conjunctive use since 1956 are indicated in Figure 23 and include Johnson City in 1967, Boerne in 1979, and Kerrville in 1981. The development and use of ground water has significant advantages over the development and use of surface water. Ground water can be developed in relatively simple stages by drilling new wells as demand for water increases. Such staged development can be financed in a timely and more cost efficient manner through water user fees rather than large capital investments and loans with interest which are characteristically associated with the development and use of surface water. Ground-water development and use requires only small amounts ofland which may be readily retained for other meaningful uses, and requires less maintenance cost because aquifers are natural, in place, relatively permanent sources of water. Also, aquifers have great longevity, are protected by natural overburden from adverse changes :aused by the activities of man at the surface, and are not effected by sedimentation which decreases the dependable yield of surfacewater resetvoirs. Ground water has negligible losses due to evaporation and requires very little treatment. Since aquifers have extensive occurrence and availabilityofwaterthatisin transit storage, they provide a natural distribution system that minimizes the size of the water distribution system at the land surface (modififd from Lehr, 1989). In Texas, ground-water use is an inherent property right and landowners may withdraw as much ground water as physically possible as long as the water is used for beneficial purposes and is not wasted. Such advantages and benefits from ground-water development and use has been realized by public water systems in the study area for many decades. However, because of the relatively poor hydraulic characteristics of the aquifers, the significantly large expected increases in the demands for water, and the inability or unwillingness or most of the public water systems to adjust to these conditions by obtaining additional lands for the proper spacing of additional wells, only a portion of the ground water available on a sustained bash• has been utilized for public water needs. Fredericksburg :lS the only major public water system which historically has explored for and successfully developed and used available ground water from the Paleozoic aquifers in areas several miles from the city. This has not been practiced by other major public water systems in the study area. Such public water systems as Kerrville and Boerne have chosen to supplement their ground-water supply from the Trinity Group aquifers with surface water from the Guadalupe River (Kerrville) and Cibolo Creek (Boerne). The City of Blanco used ground water from a local shallow alluvial aquifer until1956 when it started using surface water from the Blanco River as its main water supply until about 1970. Since 1970, Blanco has used only Evaluation of the Ground-Water Re>Ources of the Paleozoic and Cretaceous Aquifer! in the Hill Country of Texas July 1992 EXPECTED WATER DEVELOPMENT AND GROUND-WATER QUALITY PROBLEMS 113

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Evaluation of the: Ground-Water Rc:!IOllrcc:s of the: Paleozoic and Crc:tacc:oui Aquifers in rhc: Hill Country of Central Texas July 1992 114 smface water from the river and has apparently not been able or willing to explore for and develop a supplemental supply from ground water. Johnson City used ground water only up to about 1967when a supplemental supply was used from the Pedernales River up to 1970. In 1970,Johnson City only used its ground-water supply but then for the next 9 years ( 1971-1979) only used surface water from the river. In 1980, Johnson City started using ground water again to supplement its surface-water supply, and by 1987 used only ground water from an expanded well field within the city. Such histories of water development and use along with the limited productivity and performance of the aquifers within limited local areas of concentrated pumpage and the expected public water needs previously presented, indicate the public water supply development problems that can be expected to occur through the year 2010. Additional sustainable amounts of sui table quality ground water will be available for public supply purposes from the Paleozoic and Cretaceous aquifers in remote areas appropriate distances from the current centers of pumpage for public supply us
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Lake Travis (22,403 acre-feet per year permitted) and Town Lake (36,456 acre-feet per year permitted). These waters are used mainly for municipal and industrial purposes within the Austin water system. A small amount of this water is used for public supply purposes within the Travis County portion of the study area. In 1985, the LCRAand the City of Austin supplied only about 5,40fl acre-feet to the Lakeway MUD ( 1,281 acre-feet) the City of West Lake Hills (732 acre-feet) and other smaller public water systems (3,392 acre-feet) in the Travis County portion of the study area. One other major surface-water purveyor provic!es significant amounts of water for public water supply in the study area. The Upper Guadalupe River Authority (UGRA), which serves Kerr County only, holds a 3,603 acre-feet per year permit for water from the Guadalupe River. In 1985, the UGRA supplied about acre-feet of treated Guadalupe River water to the City of Kerrville. Consequently, in 1985 the BMAC WCID No. 1, the GBRA, the LCRA, the City of Austin and the UGRA which have almost 2.5 million acre-feet of annual surface-water rights from the five major reservoirs and the Guadalupe River, only supplied about 8,300 acre-feet of surface water for public water supply purposes in the study area. An explanation of this discrepancy between permitted water rights and actual water supplied to the study area is beyond the scope of this report. However, HDR Engineers, Inc. (1989), addressed the existing and potential surface-water supply problems in their Hays County regional water and wastewater study for the Hays County Water Development Board. HDR's study report addresses in detail the potential al temative water users and suppliers for Hays County and the legal institutional alternatives for delivery of surface waters for future public water use in the county. This report adequately exemplifies the problems related to the future development and use of surface water for public supplies and the conditions and arrangements needed to solve such problems for the remaining portions of the study area; particularly that portion of the study area where the Trinity Group aquifers are the only sources of ground water for public water supply purposes. If feasible, the existing surface-water supplies develo::>ed and controlled by the Cities ofKerrville,Johnson City, Blanco and Boerne may be used effectively in an expanded manner for conjunctive use in unincorporated areas within or immediately acljacent to their sen-ice in Kerr, Blanco and Kendall Counties. The Cloptin Crossing reservoir, which is proposed in the 1984 Texas Water Plan and is an authorized Corps of Engineers project for construction in Hays and Comal Counties on the Blanco River, would have been a useful water supply for the southeast portion of the study area. However, plans for this reservoir have been dropped (Cross and Bluntzer, 1990). Other potential reservoirs which are included in the 1984 Texas Water Plan and which have been considered as future water supplies include Pedernales reservoir, a proposed Corps of Engineers project on the Pedernales River northwest of Johnson City in Blanco County, and Ingram reservoir, a proposed Upper Guadalupe River Authority project on Johnson Creek northwestofKe:rrville in Kerr County. The Dripping Springs reservoir which is a proposed wc:.ter supply from Onion Creek has been considered in a Hays County water and wastewater study for the Hays County Water Development Board (HDREngineering, Inc., 1989) as a potential surface-water supply for the Dripping Springs area. If feasible, perhaps these and other proposed reservoirs and surface-water diversions could be used to provide adequate surface-water mpplies for future meaningful conjunctive use with appropriately developed ground water in the study area. Evaluation of the Ground-Water Re!IOurces of the Paleozoic July 1992 115

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifen in the Hill Country of Central Texas July 1992 116 Since the Paleozoic and Cretaceous aquifers have very limited amounts of ground-water that can be recovered on a practical basis to meet the large public water supply needs expected to occur through the year 2010, it is imperativethatadditionalamountsofacceptablequalitywaterbedeveloped and utilized. Such additional waters may be made available from the large amounts of surface water known to exist within and immediately adjacent to the study area. The development and use of such surface waters for public water supplies will only be achieved through well planned cooperative arrangements and actions by the existing and potential water purveyors and users within and adjacent to the study area. The area's future public water supply development problems can be and should be appropriately solved through well planned and implemented corUunctive use of ground water and surface water. However, such a solution which involves the development and use of surface water will be very costly and public water users will need to be prepared to make arrangements to adequately address and meet such costs. For this reason, public water systems which currently use ground water should retain this established source of water supply because such supply is in place and can continue to be utilized at some specific sustained level of development at a minimum of cost to water users. On a long-term basis, if sufficient surface-water supplies can not be made available to adequately meet the area's public water supply needs, then additional ground water will have to be developed in remote areas some appropriate distances from existing centers of concentrated pumpage. This additional development of ground waters in remote areas also will be costly. The ground-water resources have been identified as having moderate to serious water-quality problems related to unusually high to excessive concentrations of nitrate, fluoride, sulfate, alpha radiation and radium. Since public water supply systems are being required to meet EPA primary and secondary drinking water standards, future public water supply wells should be carefully and selectively tested, sampled, and analyzed for various chemical constituents before being developed into production wells. Such water quality testing should definitely include analyses for nitrate, fluoride, sulfate, alpha radiation, and total radium. If unusually high to excessive concentrations of these constituents and radiation are detected, production wells may be properly constructed to avoid them or another safer drinking water supply may have to be developed.

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The Hill Country area addressed in this report covers about 5,539 square miles in all or parts of Bandera, Blanco, Co mal, Gillespie, Hays, Kendall, Kerr, Medina, and Travis Counties of c:entral Texas. Within this area, ground-water supplies are obtained from eight aquifers of Paleozoic and Cretaceous ages. The older Paleozoic aquifers include from oldest to youngest the Hickory, the Mid-Cambrian, the Ellenburger-San Saba, and the Marble Falls. The younger Cretaceous aquifers include from oldest to youngest the Lower Trinity, the Middle Trinity, the Upper Trinity, and the Edwards Plateau. Due to stratigrahpic positioning and faulting, these aquifers are hydrologically connected and form leaky aquifer systems in much of the study area. Also, these eight aquifers naturally discharge a significant amount of spring flow, are known to to be hydrologically connected to area streams, and consequently, contribute base flow to effiuent reaches of the major rivers and creeks within the study area. During the 1980's, about 60 percent of the water used in the area was supplied by the eight aquifers. Of the 18,739 acre-feet of ground water used in 1985, about 74 percent was used for drinking and household purposes (public supply and domestic uses). On an average annual basis the Paleozoic and Cretaceous aquifers are replenished with about 450,000 acre-feet of natural recharge. However, due to the erratic occurrence of ground water and the low coefficients of transmissibility and storage of these aquifers only about 46,000 acre-feet per year can be considered as the sustained yield. Consequently, undesirable water-level declines occur in areas of concentrated withdrawals for public supply where storage has been seriously depleted, pumping lifts increased and well yields greatly reduced. Unusually high to excessive concentrations of nitrate have been detected in the waters produced from the shallow portions of the aquifers. Nitrate pollution is most evident in the Edwards Plateau aquifer in the western portion of the study area, and appears to be increasing. Such pollution which is believed to be caused by livestock and wildlife excrements (animal wastes) threatens the safe use of the ground water for drinking purposes and the water quality of the base flow to area effluent streams. Inherently high to excessive concentrations of fluoride are found in the water in the deeper portions of the Lower Trinity aquifer. The anhydrite and gypsum beds in the Glen Rose Formation and in some parts of the Travis Peak Formation are the sources of the unusually high to excessive concentrations of sulfate in the waters produced from the Upper and Middle Trinity aquifers. The fluoride and sulfate problems in many cases can be avoided byproperwell construction, completion, and development. The solutions to these ground-water availability and guality problems can be attained by the conjunctive use of ground and surface waters and by the management and protection of the ground-water resources. Such conjunctive use has been and is currently being practiced successfully at Kerrville, Evaluation of the Ground-Water Resources of the P..Aleozoic and Cretaceous A9uifers in the Hill Country of Central Texa• July 1992 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 117

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Evaluation or the Ground-Water Resources or the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Tens July 1992 118 Boerne, and Johnson City. Public water systems which should initiate conjunctive use are Bandera, Comfort, Fredericksburg, Ingram, Blanco, Woodcreek, and Wimberly. If conjunctive use is not possible, such public water systems should make earnest attempts to seek additional groundwater supplies in remote areas away from their current wells to avoid undesirable water-level declines and associated depletion of storage, excessive pumping lifts, and reductions in well yields and specific capacities. Ground-water management and protection could be accomplished by each individual public water system or through a larger govern men tal entity such as a local or a regional underground water conservation district. In either case, each management and protection entity should establish and maintain: 1) a comprehensive data collection program concerned with the monitoring of water levels, water quality, and pumpage;; 2) a program that monitors the effects of ground-water development on the base flow to area streams; 3) a strategic management plan; 4) a well c:onstruction, completion, and development program; 5) a pumpage control program; 6) where practical, an artificial recharge program; 7) a water conservation program; 8) a water education program; and 9) where practical, a surface-water acquisition program. Currently, the Hill Country area covered by this report has two local water management and protection entities, namely the Hill Country Underground Water Conservation District which serves Gillespie County and the Spring hills Water Management District (a combined surface-water and ground-water conservation district) which serves Bandera County.

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 SELECTED REFERENCES Advisory Committee for Hill Country Study Area, 1988, Advisory committee member responses to questionnaire on ground-water critical area two, 23 p. Alexander, W. H., Jr., Meyers, B. N., and Dale, 0. C., 1964, Reconnaissance investigation of the ground-water resources of the Guadalupe, San Antonio, and Nueces River basins, Texas: Texas Water Commission Bulletin 6409, 105 p. Allison,]. E., Dittmar, G. W., and Hensell,J. L., 1975, Soil survey of Gillespie County, Texas: U.S. Department of Agriculture, Soil Conservation Service, 80 p. Arnow, Ted, 1957, Records ofwells in Travis County, Texas: Texas Board ofWater Engineers Bulletin 5708, 129 p. Ashworth, J. B., 1983, Ground-water availability of the Lower Cretaceous formations in the hill country of southcentral Texas: Texas Department of Water Resources Report 273, 182 p. Barnes, B. A., 1938, Records of wells and springs in Hays County, Texas: Texas Board ofWater Engineers duplicate report, 30 p. Barnes, B. A., and Cumley,J. C., 1942, Records ofwells and springs in Blanco County, Texas: Texas Board ofWater Engineers duplicate report, 55 p. Barnes, V. E., 1948, Ouachita facies in central Texas: University ofTexas, Bureau of Economic Geology Report Inv. no. 2, 12 p. _, 1952-1956, Geologic maps, scale 1:31,680, of7.5-minute quadrangles, Gillespie and adjoining counties: Univ. Texas, Bureau of Economic Geology Geol. Quad. Maps 1-20. __ , 1963, Correlation of Cambrian rocks in central Texas: University of Texas, Bureau of Economic Geology, Miscdlaneous chart (preliminary edition). _, 1963-1982, Geologic maps, scale 1:24,000, of 7.5-minute quadrangles, Blanco and adjoining counties: University of Texas, Bureau of Geology Geol. Quad. Maps 25, 27, 29, 31-34, 43, 44, 46, 47, and 49-51. Barnes, V. E., Cloud, P. E., Dixon, L. P., Folk, R. L.,Jonas, E. C., Palmer, A. R., and Tynan, E.J., 1959, Stratigraphy of the pre-Simpson Paleozoic subsurface rocks of Texas and southeast New Mexico: University of Texas, Bureau of Economic Geology Publication 5924, v. 1, 294 p., v. 2, 836 p. Barnes, V. E., and Bell, W. C., 1977, The Moore Hollow Group of central Texas: University of Texas, Bureau of Economic Geology Report, Inv. no. 88, 169 p. Barnes, V. E., Bell, W. C., Clabaugh, S. E., Cloud, P. E.,Jr., McGehee, R. V., Rodda, P. U., and Young, K P., 1972, Geology of the Llano region and Austin area: Univ.ersity ofTexas, Bureau of Economic Geology Guidebook no. 1:3, 77 p. Barnes, V. E., Romberg, F. E., and Anderson, W. A., 1954, Correlation of gravity and magnetic observations with the geology ofBlanco and Gillespie Counties, Texas in San Angelo Geological Society (Guidebook) Cambrian Field trip-Llano area, March 1954, pp. 78-90. __ , 1955, Map showing correlation of geologic, gravity and magnetic observations, Blanco and Gillespie counties, Texas: University of Texas, Bureau of Economic Geology map. Batte, C. D., 1984, Soil survey ofComal County, Texas: U.S. Department of Agriculture, Soil Conservation Service, 136 p. 119

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Evaluation or the Ground-Water Resources or the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Bebout, D. G., Budd, D. A., and Schatzinger, R. A., 1981, Depositional and digenetic history of the Sligo and Hosston Formations (Lower Cretaceous) in south Texas: University of Texas, Bureau of Economic Geology, Report Inv. no. 109, 69 p. Bebout, D. G., and Loucks, R. G., 1974, Stuart City trend, lower Cretaceous, south Texas, a carbonate shelf-margin model for hydrocarbon exploration: University ofTexas, Bureau Economic Geology Report lnv. no. 78, 80 P Bluntzer, R. L., 1988, Evaluation of the Hickory aquifer and its relationship to Katemcy Creek and its major tributaries for beneficial artificial recharge, McCulloch and Mason Counties, Texas: Texas Water Development Board memorandum rept. for the Hickory Underground Water Conservation District No 1. Boone, P. A., 1968, Stratigraphy of the basal Trinity (Lower Cretaceous) sands of central Texas: Baylor University, Baylor Geological Studies Bulletin 15, 64 p. Bouwer, Herman, 1990, Agricultural chemicals and ground-water quality, issues and challenges (Forum): Ground Water MonitDring Review, Winter 1990, pp. 71-79. Breeding, S. D., and others, 1964, Fifty years of water development in Texas: Texas Water Commission Bulletin 6403,23 p. Bridge,Josiah, Barnes, V. E., and Cloud, P. E.,Jr., 1947, Stratigraphy of the upper Cambrian, Llano uplift, Texas: Geological Society of America Bulletin, v. 38, no. 1, pp. 109-124. Broadhurst, W. L.. Sundstrom, R. W., and Rowely, J. H., 1950, Public water supplies in southern Texas: U. S. Geological Survey Water-Supply Paper 1070, 114 p. Brune, Gunnar, 1975, Major and historical springs ofTexas: Texas Water Development Board Report 189, 95 p. Brune, Gunnar, and Duffin, G. L., 1983, Occurrence, availability and quality of ground water in Travis County, Texas: Texas Department of Water Resources Report 276, 225 p. Burden, E. H. W. J ., 1961, The toxicology of nitrates with particular reference to the potability of water supplies: The Analyst, Soc. Anal. Chern. Proc., v. 86, no. 1024, pp. 429-433. Bybee, H. P., 1952, The Balconesfaultzone-an influence on human economy: Texas journal Sci., v. 4, no. 3, pp. 387392. Bureau of Economic Geology, 1974a, Geologic atlas of Texas, Austin sheet: University of Texas, Bureau of Economic Geology map. __ , 1974b, Geologic atlas ofTexas, San Antonio sheet: University of Texas, Bureau of Economic Geology map. __ , 1974c, Geologic atlas ofTexas, Seguin sheet: University of Texas, Bureau of Economic Geology map. __ , 198t, Geologic atlas ofTexas, Llano Sheet: University of Texas, Bureau of Economic Geology map. Bush, P. W., 1986, Planning report for the Edwards-Trinity regional aquifer-systems analysis in central Texas, southeast Oklahoma, and southwest Arkansas: U.S. Geological Survey Water-Resources Inv. Rept. 86-4343, 15 P Canter, L. W., and Knox, R. C., 1985, Septic tank system effects on ground water quality: Lewis Publishers, Inc., Chelsea, Michigan, 336 p. Caran, S. C., Woodruff, C. M., Jr., and Thompson, E. J., 1982, Lineament analysis and inference of geologic structure-examples from the Balcones;'Ouachita trend ofTexas: University of Texas, Bureau of Economic Geology, Geology Circular 82-1, 12 p. 120

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Evaluation of the Ground-Water Re!IOurccs of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Cech, Irina, and others, 1988, Radon distribution in domestic water ofTexas: Ground Water, v. 26, no. 5, pp. 561569. Cheney, M. G., and Goss, L. F., 1952, Tectonics of central Texas: American Association of Petroleum Geologist, Bulletin, v. 36, no. 12, pp. 2237-2265. CH2M Hill. 1988, Aquifer storage recovery feasibility investigation, phase 1-preliminary assessment: Prepared for the Upper Guadalupe River Authority by CH2M Hill, San Antonio, Texas, 50 p. __ , 1989, Aquifer storage recovery feasibility investigation, phase IIA-monitoring well PZ-1, v.I-Report, v. 11-appendices: Prepared for the Upper Guadalupe River Authority by CH2M Hill, Austin, Texas. Cloud, P. E.., Jr., and Barnes, V. E., 1946, The Ellenburger Group of central Texas: University of Texas, Bureau of Geology Pub. 4621, 473 p. Cobb, C. E., 1989, Living with radiation: National Geographic, v. 175, no. 4, (April1989), pp. 403-437. Cross, B. L., and Bl un tzer, R. L., 1990, Ground-water protection and management strategies for the hill country area -a critical area ground-water study: Prepared for the Texas Water Comm., 19 p. Cuyler, R.H., 1931, Vegetation as an indicator of geologic formations: American Association ofPetroleum Geologists Bulletin, v. 15, pt. 1, pp. 67-78. __ , 1939, Peak, formation of central Texas: American Association of Petroleum Geologists Bulletin, v. 23, no. 5, pp. 625-642. Dallas Morning News, 1989, 1990-91 Texas almanac: Texas Monthly Press, Austin, Texas, 607 p. DeCook, KJ., 1960, Geology and ground-water resources of Hays County, Texas: Texas Board ofWater Engineers Bulletin 6004, 170 p. DeCook, K.J., and Doyel, W.W., 1955, Records of wells in Hays County, Texas: Texas Board of Water Engineers Bulletin 5501, 60 p. Dittemore, W. H., Jr., and Allison,]. E., 1979, Soil survey of Blanco and Burnet Counties, Texas: U.S. Department of Agriculture, Soil Conservation Service, 116 p. Dittemore, W. H.,Jr., and Coburn, W.C., 1986, Soil survey of Kerr County, Texas: U.S. Dept. Agric., Soil Conserv. Serv., 123 p. Dittemore, W. H.,Jr., and Hensell,J. L., 1981, Soil surveyofKendall County, Texas: U.S. Department of Agriculture, Soil Conservation Service, 87 p. Dittmar, G. W., Deike, M. L., and Richmond, D. L., 1977, Soil survey of Medina County, Texas: U.S. Department of Agriculture, Soil Conservation Service, 92 p. Doll, W. L., Meyer, G., and Archer, RJ., 1963, Water resources ofWest Virginia: West Virginia Department ofN at ural Resources, Div. Water Resources, 134 p. Dowell, C .L., and Petty, R.G., 1971, Dams and reservoirs in Texas, pt. III: Texas Water Development Board Rept. 126,86 p. Driscoll, F. G., (author and editor), 1986, Groundwater and wells: johnson Division, Saint Paul, Minnesota, 1,089 P Duffin, G. L., 1974, Subsurface saline water resources in the San Antonio area, Texas: Texas Water Development Board dupl. rept., 39 p. 121

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Evaluation of the Ground-Water Rc110urces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Eaton, F. M., 1950, Significance of carbonates in irrigation waters: Soil Sci., v. 59, pp. 123-133. Espey, Huston and Associates, Inc., 1985, Data report-septic tank loadings to Lake Travis and Lake Austin: Prepared for the Lower Colo. River Auth. and Texas Dept. Water Resources, Espey Huston, and Assoc., Inc., Doc. No. 85782, 6'i' p. Fisher, W. L., and Rodda, P. U., 1967, Lower Cretaceous sands of Texas, stratigraphy and resources: Univ. Texas, Bur. Econ. Geology Rept. Inv. no. 59, 116 p. Flawn, P. T., 1956, Basement rocks of Texas and southeast New Mexico: University of Texas, Bureau of Economic Geology Publication 5605, 261 p. Flawn,P. T., Goldstein,A.,Jr., King,P. B., and Weaver, C. E., 1961, TheQuachitasystem: UniversityofTexas, Bureau of Economic Geology, Pub. 6120,385 p. Follett, C. R., 1956a, Records ofwater-level measurements in Comal and Guadalupe Counties, Texas: Texas Board Water Engineers Bull. 5610, 32 p. __ , 1956b, Records ofwater-level measurements in Hays, Travis, and Williamson Counties, Texas, 1937 to May 1956: Texas Board Water Engineers Bulletin 5612, 74 p. _, 1956c, Records ofwater-level measurements in Medina County, Texas, 1930 to March 1956: Texas Board of Water Engineers Bulletin 5609, 24 p. _, 1973, Ground-water resources of Blanco County, Texas: Texas Water Development Board Report 174, 95 p. ForgotsonJ. M.,Jr., 1956, A correlation and regional stratigraphic analysis of the formations of the Trinity Group of the Comanchean Cretaceous of the Gulf Coastal Plain; and The genesis and petrography of the Ferry Lake Anhydrite: Northwestern Univ., Ph.D. dissertation. (Summary in Gulf Coast Assoc. Geol. Socs. Trans., v. 6, pp. 91-108.) Frazier,]. M.,Jr., 1940, Records of wells in Kendall County, Texas: Texas Board Water Engineers dupl. rept., 26 P Friebele, C. D., and Wolff, H. A., 1976, Annotated bibliography of Texas water resources reports: Texas Water Development. Board Report 199, 156 p. Garner, L. E., and Young, K. P., 1976, Environmental geology of the Austin area-an aid to urban planning: University of Texas, Bureau of Economic Geology Report Inv. no. 86, 39 p. George, W. 0., 1952, Geology and ground-water resources of Co mal County, Texas, with sections on surface-water runoff by S.D. Breeding, and chemical character of the water by W. W. Hastings: U.S. Geological Survey Water Supply Paper 1138, 126 p. George, W. 0., and Bennett, R. R., 1942, Ground-water resources in the area between Buda and San Marcos, Hays County, Texas: Texas Board of Water Engineers open-file rept., 8 p. George, W. 0., Cumley,J. C., and Follett, C. R., 1941, Records ofwells and springs in Travis County, Texas: Texas Board of Water Engineers dupl. rept., 101 p. George, W. 0., and Doyel, W. W., 1952, Ground-water resources in the vicinity of Kenmore farms in Kendall County, Texas: Texas Board of Water Engineers Bulletin 5204, 9 p. George, W. 0., and Follett, C. R., 1945, Ground-Water resources in the vicinity of Kyle, Texas: Texas Board Water Engineers manuscript rept. 122

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Evaluation of Rc10urces of the Pakozoic and Aquifers in Hill Country ofc'-entrdl Texas July 1992 George, W. 0., and Hastings, W. W., 1951, Nitrate in ground water in Texas: American Geophys. Union Trans., pp. 450-456. George, W. 0., and Welder, F. A., 1955, Geology of the Canyon Reservoir site on the Guadalupe River, Comal County, Texas: U. S. Geological Survey open-file rept. Ground Water Prottction Committee, 1988, Texas ground-water protection strategy: Texas Water Commission, 104 P Guyton, W. f'. &Associates, 1955, The Edwards's limestone reservoir: ConsultantreportpreparedfortheCityWater Board, San Antonio, Texas, 30 p. __ , 1958, Recharge to the Edwards reservoir between Kyle and Austin: Consultant rept. prepared for the City Water Board, San Antonio, Texas, 9 p. __ , 1973, Report on ground-water conditions in the Kerrville area in Upper Guadalupe River Authority-City of Kerrville water supply study report: Prepared for the Upper Guadalupe River Authority by Turner, Collie & Braden, Inc.,.January 1974, Appendix A, 37 p. __ , 1979, Geohydrology of Comal, San Marcos, and Hueco Springs: Texas Department of Water Resources Report 234, 85 p. HDR Engineering, Inc., 1989, Hays County regional water and wastewater study: Prepared for the Hays County Water Develcpment Board through cooperative funding provided by the Texas Water Devel. Board, HDR Engineering, Inc., Austin, Texas, 179 p., (includes executive summary). Heller, V. G., 193g, The effect of saline and alkaline waters on domestic animals: Oklahoma A & M College, Experimental Station Bulletin 217, 23 p. Hem,]. D., 1985, Study and interpretation of the chemical characteristics of natural water: U.S. Geological Survey Water-Supply Paper 2254, 3rd. ed., 263 p., (1st ed. and 2nd. ed. were USGS WSP 1473 in 1959 and 1970 respectively). Hendricks, C. L., 1952, Correlation between surface and subsurface sections of the Ellenburger Group of Texas: Univ. Texas, Bureau of Economic Geology Report Inv. no. 11, 44 p. Hendry, Jim, 1988, The nitrate problem: Water Well Journal, v. 42, no. 8, pp. 4-5. Henningsen, R. E , 1962, Water diagenesis in Lower Cretaceous Trinity aquifers of central Texas: Baylor Univ., Baylor Geological Studies Bull. 3, 38 p. Hensell,J. L., Dittmar, G. W., and Taylor, F. B., 1977, Soil survey ofBandera County Texas: U.S. Dept. Agric., Soil Conserv. Serv., 49 p. Hill, R. T., 1901, Geography and geology of the Black and Grand Prairies, Texas: U.S. Geological Survey, Twenty first Annual Report, pt. 7, 666 p. Hill, R. T., and Vaughan, T. W., 1898, Geology of the Edwards Plateau and Rio Grande Plain adjacent to Austin and San Antonio, Texas with reference to the occurrence of underground waters: U. S. Geological Survey, Eighteenth Annual Report pt. 11, pp. 193-321. __ , 1902, Austin, Texas quadrangle: U.S. Geological Survey, Geologic Atlas of the U.S. Folio 76. Holland, P. H., 1962, Base-flow studies, Guadalupe River, Comal County, Texas, quantity, March 1962: Texas Water Commission Bulletin 6503, 6 p. 123

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Holland, P. H., and Medieta, H. B., 1965, Base-flow studies, Uano River, Texas, quantity and quality: Texas Water Commission Bulletin 6505, 20 p. Holmquest, H. J.,J:r., 1955, Structural development of west-central Texas, in Abilene Geological Society Guidebook 1955, pp.19-32. Holt, C. L. R., 1956, Geology and ground-wat(!r resources ofMedina County, Texas: Texas Board ofWater Engineers Bulletin 5601, 289 p. Huisman, L., and Olsthoorn, T. N., 1983, Artificial groundwater recharge: Pittman Publishing, Inc., Marshfield, Mass., 320 p. Hurlburt, Scott, 1988, The problem with nitrates: Water Well journal, v. 42, no. 8, pp. 37-42. Imlay, R. L., 1945, Subsurface Lower Cretaceous formations of south Texas: American Association of Petroleum Geologists Bulletin, v. 29, no. 10, pp. 1416-1469. Jones, D. C., 1973, An investigation of the nitrate problem in Runnels County, Texas: U. S. Environmental Protection Agency, Office of Research and Monitoring, Environmental Protection Technology Series EPA R2-73-267 (Project 16060HNI), 24 p. Kaiser, R. A., 1987, Handbook of Texas water law-problems and needs: Texas A&M University, Texas Water Resources In:;titute, EIS 86-236 1/87-2M, 46 p. Kent, R. T., 1975, Ceo logic factors influencing the operation of septic tank systems in Travis County, Texas (abst.): Geological Sociecty of America, Abstracts with Programs, v. 7, no. 2, p. 178. Klemt, W. B., Perkins, R. D., and Alvarez, H.J., 1975, Ground-water resources of part of central Texas with emphasis on the Antlers and Travis Peak Formations: Texas Water Development Board Report 195, v. 1, 63 p. Kuniansky, E. L., 1989, Precipitation, streamflow and base flow in west-central Texas, December 1974 through March 1977: U.S. Geological Survey Water-Resources lnv. Report 88-4218, 2 folio sheets. Kunze, H. L., and Smith,]. T., 1966, Base-flow studies, upper Guadalupe River basin, Texas, quantity and quality, March 1965: Texas Water Development Board Report 29,33 p. Lang,]. W., 1953, Ground water in the Trinity Group in the San Antonio area, Texas: U.S. Geological Survey openfile rept., 4 p. __ , 1954, Ground-water resources of the San Antonio area, Texas-a progress report of current studies: Texas Board of Water Engineers Bulletin 5412, 30 p. Lappenbusch, W. L, 1988, Contaminated waste sites, property and your health: Lappenbusch Environmental Health, Inc., Alexandria, Virginia, 360 p. Larkin, T. J., and Bomar, G. W., 1983, Climatic atlas ofTexas: Texas DepartmentofWater Resources LP-192, 151 P Lehr, J. H., 1989, Public education-your responsibility: Water Well jour., v. 43, no. 12, pp. 4-5 Livingston, Penn, 1940, Ground-water conditions in vicinity of reservoir site on Cibolo Creek at Boerne Texas: U. S. Geological Survey open-file rept. Lonsdale,]. T., Igneous Rocks of the Balcones Fault region of Texas: University of Texas Bulletin 2744. Loucks, R. G., and others, 1978, Lower Cretaceous carbonate tidal facies of central Texas: University of Texas, Bureau of Economic Geology, research note, 45 p. 124

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Lowry, R. L., 1955 .. Recharge to the Edwards ground-water reseiVoir: Consultant report prepared for the City Water Board, San Antonio, Texas, 66 p. Lowry, R. L.,Jr., 1960, Monthly reseiVoir evaporation rates for Texas, 1940 through 1957: Texas Board Water Engineers Bull. 6006, 95 p. Lozo, F. E., and Stricklin, F. L.,Jr., 1956, Stratigraphic notes on the outcrop basal Cretaceous, central Texas: Trans. Gulf Coast Assoc. Geological Society, v. 6, p. 67-78. Lozo, F. E., and others, 1959 Symposium on Edwards limestone in central Texas: University of Texas, Bureau of Economic Geology Publication 5905, 235 p. Lyerly, P.]. and Longenecker, D. E., 1957, Salinity control in irrigation agriculture: Texas A & M Univ., Texas Agricultural Extension Service Bulletin 876, 20 p. Maier, F.J., 1950, Fluoridation of public water supplies: American Water Works Association journal, v. 42, part 1, pp. Mason, C. C., 1961, Ground-water geology of the Hickory Sandstone Member of the Riley Formation, McCulloch County, Texas: Texas Board of Water Engineers Bulletin 6017, 84 p. Maxcy, K. F., 1950, Report on the relation of nitrate concentration in well waters to the occurrence of methemoglobinemia in infants: National Research Council Bulletin Sanitary Engineering and Environment, Appendix D, pp. 265-271. Maxwell, R. A., Brown, L. F.,Jr., Eifler, G. K., and Gamer, L. E., 1970, Geologic and historic guide to the state parks of Texas: University of Texas, Bureau of Economic Geology Guidebook 10, 188 p. Meinzer, 0. E., 1927, Large springs in the United States: U.S. Geological SuiVey Water-Supply Paper 557. _1946, General principles of artificial ground-water recharge: Economic Geology., volume 41, pp. 191-201. Meyers, B. N., 1969, Compilation of results of aquifer tests in Texas: Texas Water Development Board Report 98, 532p. Michal, E. J., 1937, Records ofwells and springs in Comal County, Texas: Texas Board ofWater Engineers dupl. rept., 44 p. Moore, C. H.,Jr., 1964, Stratigraphy of the Fredericksburg division, south-central Texas: UniversityofTexas, Bureau of Economic Geology Report Inv .. no. 52, 48 p. Morris, D. A., and johnson, A. I., 1967, Summary of hydrologic and physical properties of rock and soil materials, as analyzed by the Hydrologic Laboratory of the U.S. Geological SuiVey, 1948-60: U.S. Geological Survey Water-Supply Paper 1839-D, 42 p. Mount,]. R., 1963, Investigation of ground-water resources near Fredericksburg, Texas: Texas Water Commission Memo. Report no. 63-03, 115 p. Mount,]. R., Rayner, F. A., Shamburger, V. M.,Jr., Peckham, R. C., and Osborne, F. L.,Jr. 1967, Reconnaissance investigation of the ground-water resources of the Colorado River basin, Texas: Texas Water Development Board Report 51, 107 p. Muller, D. A., 1990, Ground-water evaluation in and adjacent to Dripping Springs, Texas: Texas Water Development Board Rept. 322, 61 p. Muller, D. A., and McCoy, Wesley, 1987, Ground water conditions of the Trinity Group aquifer in western Hays County: Texas Water Development Board LP-205, 62 p. 125

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Evaluation of the Ground-Watc:r Resources of the Paleozoic and Cretaceous Aqu tfers in the Hill Country of Central Texas July 1992 Muller, D. A., and Price, R. D., 1979, Ground-water availability in Texas: Texas Deparunent of Water Resources Report 238, p. Namy,J. N., 1969, Stratigraphy of the Marblle Falls Group, southeast Burnet County, Texas: University of Texas, Ph.D. dissertation, 385 p. Nugent, Mike, and Kamrin, Michael, 1988, Nitrate-adrinkingwaterconcern: CenterofEnvironmental Toxicology and Institute of Water Research, Michigan State University brochure, 4 p. Nordstrom, P. L., 1988, Occurrence and quality of ground water in jack County, Texas: Texas Water Development Board Rept. 87 p. O'Hare, M.P., Fairchild, D. M., Hajali, P. A.., Canter, L. W., 1986, Artificial recharge of ground water, status and potential in the contiguous United States: Lewis Publishers, Inc., Chelsea, Michigan, 419 p. Palmer, A. R., 1954, The faunas of the Riley Formation in central Texas: University of Texas, Bureau of Economic Geology Report Inv. no. 24, 78 p. Perkins, B. F., 1968, Geologyofa rudist-reef complex (abst.): Geological Society of America Program, 81stAnnual Meeting, p. 223. _, 1970, Genetic implications of rudist reef architecture (abst.): Amer. Assoc. Petrol. Geologists Bull., v. 54, pp. 863-864. Pettit, B. M.,Jr., and George, W.O., 1956, Ground-water resources of the San Antonio area, Texas: Texas Board Water Engim:ers Bull. 5608, v. 1, 85 p.,, __ and v. 2, pt. 1, 255 p. Plummer, F. B., 1943, The Carboniferous rocks of the Llano regional of central Texas: University ofTexas, Bureau of Economic Geology Publication 4329, 170 p. Pyne, R. D. G., 1987 .Aquifer storage recovery, current status in the United States: International Symposium on Class V Injection \Veil Technology, September 22-24, 1987, Washington D. C., 11 p. Reeves, R. D., 1967, Ground-water resources of Kendall County, Texas: Texas Water Development Board Report 60, 108 p. __ , 1969, Ground-water resources of Kerr County, Texas: Texas Water Development Board Report 102, 71 p. Reeves, R. D., and Lee F. C., 1962, Ground-water geology of Bandera County, Texas: Texas Water Commission Bulletin 6210, 78 p. Rhoades, Roger, and Guyton, W. F., 1955, Proposed Canyon Reservoir, Guadalupe River, a study of ground-water hydrology and geology: Consulting report to City Water Board, San Antonio, Texas. Rodda, P. U., Payne, W.R., and Schofield, D.A., 1966, Limestone and dolomite resources, Lower Cretaceous rocks, Texas: University ofTexas, Bureau of Economic Geology Report Inv. no. 56, 286 p. Rose, P.R., 1972, Edwards Group, surface and subsurface, central Texas: UniversityofTexas, Bureau ofEconomic Geology Report Inv. no. 74, 198 p. Sayre, A. N., 1936, Geology and ground-water resources of Uvalde and Medina Counties, Texas: U.S. Geological Survey Water-Supply Paper 678. Sayre A. N., and Bet1nett, R. R., 1942, Recharge, movement, and discharge in the Edwards Limestone reservoir, Texas: American Geophys. Union Trans., pt. 1. 126

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Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Sayre, A. N., and Stringfield, V. T., 1948, Artificial recharge of ground-water reseiVoirs: American Water Works AssocciationJoumal, v. 40, p. 1152-1158 Schmitz,J. T., 1961, Methemoglobinemia-acauseofabortions?: Obstetrics and Gynecology, v.17, no. 4, pp. 413415. Scofield, C. S., 1936, The salinity of irrigation water: Smithsonian Institute Annual Report, 1934-35, pp. 275-287 _ Sellards, E. H., 1930, Report on underground water conditions at Fredericksburg: University of Texas, Bureau of Economic Geology open-file rept., 5 p. ___ , 1931, Rocks underlying Cretaceous in Balcones fault zone of central Texas: American Association of Petroleum Geologists Bulletin, vol. 15, pp. 819-827 Sellards, E. H., Adkins, W. S.,andPlummer, F. B., 1932, ThegeologyofTexas, v.1, Stratigraphy: UniversityofTexas, Bureau of Economic Geolgoy Bulletin 3232, 1007 p. Sellards, E. H., and Baker, C. L., 1934, The geology of Texas, v. 2, Structural and exonomic geology: University of Texas, Bureau of Economic Geology Bulletin 3401, 884 p. Senger, R. K., and Kreitler, C. W., 1984, Hydrogeology of the Edwardsaquifer,Austin area, central Texas: University of Texas, Bureau of Economic Geology Report Inv. no. 141, 35 p. Shields, Elgean, 1937, Records of wells in Gillespie County, Texas: Texas Board ofWater Engineers dupL rept., 51 P Sieh, T. \V., 197!>, Edwards (Balcones Fault Zone) aquifer test well drilling investigation: Texas Dept. Water Resources dupl. rept., 117 p. Signor, D. C., Growitz, D. J., and Kam, William, 1970, Annotated bibliography on artificial recharge of ground water, 1955-1967: U.S. Geol. SuiVeyWater-SupplyPaper 1990. Stricklin, F. L.,Jr., Smith, C.I., and Lozo, F. E., 1971, Stratigraphy oflower Cretaceous Trinity deposits of central Texas: University of Texas, Bureau of Economic Geology Report Inv. no. 71, 63 p. Sun, R. J., editor, 1986, Regional aquifer-system analysis program of the U. S. Geological SuiVeysummary of projects, 1978-84: U.S. Geological SuiVey Circular 1002, 264 p. Sunstrom, R. W.,Broadhurst, W. L.,and Dwyer,B. C., 1949, Publicwatersuppliesin central and north central Texas: U.S. Geological SuiVey Water-Supply Paper 1069, 128 p. Texas Board Water Engineers, 1958, Texas water resources planning at the end of the year 1958-a progress report to the 56th Legislature: Texas Board of Water Engineers dupl. rept. __ , 1960a, Channel gain and loss investigations, Texas streams, 1918-1958: Texas Board of Water Engineers Bulletin 5807-D, 270 p. __ , 1960b, Monthly reseiVoir evaporation rates for Texas, 1940 through 1957: Texas Board of Water Engineers Bulletin 6006, 95 p. Texas Department of Health, 1970, Individual home water-supplies: Texas Department of Health pamphlet, stock no. 2-19, 46 p. __ , 1988a, Construction standards for on-site sewerage facilities: Texas Department of Health, Division of Water Hygiene dupl. rept. 127

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Evaluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 __ , 1988b, Drinking water standards governing drinking water quality and reporting requirements for public water supply systems: Texas Department of Health, Division of Water Hygiene dupl. rept. Texas Department of Water Resources, 1977, Water planning files concerned with ground-water availability by county-basin (counties in Colorado and Guadalupe River basins): Texas Dept. Water Resources planning files. __ , 1984, Water for Texas, a comprehensive plan for the future: Texas Department of Water Resources GP-41, v. 1 and v. 2. ___ , 1985, Water use, projected water requirements, and related data and information for the metropolitan statistical areas in Texas: Texas Department ofWater Resources LP-201, 226 p. Texas State Soil and Water Conservation Board, 1988, Assessment of agricultural and silvicultural non point source water pollution in Texas: Texas State Soil and Water Conservation Board publication. Texas Water Commission, 1987, Activities-underground water conservation districts: Report to the 70th Legislature, 31 p. ___ , 1989, Ground-water quality of Texas, an overview of natural and man-affected conditions: Texas Water Commission Report 89-01, 197 p. Texas Water Commission, and others, 1988, Nonpoint source water pollution assessment report for the State of Texas: 601 p. Texas Water Development Board, 1968, The Texas water plan: Texas \Vater Development Board published comprehensive and summary repts. ___ , about 1974 (undated), Hydrologic data refinement, volume 1, objectives, procedures and methodology: Texas Water Development Board dupl. report, 88 p. ___ , 1980, 1984, and 1985, Estimates of ground-water pumpage by basin, by county, by aquifer: Texas Water Development Board planning files. __ , 1988, Historical and projected population and water use for ground-water critical area two: Texas Water Development Board planning files. __ , 1989a, Information and data on existing and proposed surface-water resources developments for groundwater critical area two: Texas Water Development Board planning files. ____ , 1989b, Apparent base flow in acre-feet (monthly, yearly and mean annual estimates): Texas Water Development planning files. __ , 1989c, Abundance, sources, form of occurrence, concentration, significance, maximum constituent level, and method of removal for selected dissolved chemical constituents and related properties of water: Texas Water Development Board Form 890088,July 25, 1989, 15 p. _, 1 989d, Surveys ofirrigation in Texas-1 958, 1964, 1969, 1974, 1979, 1984, and 1989: Texas Water Development Board Report 329, 125 p. Theis, C.V., 1935, The relation between the lowering of the piezonmetric surface and the rate and duration of discharge of a well using ground-water storage: American Geophy. Union Trans., 16th Annual Meeting. Part. 2, pp. 519-524. Thornthwaite, C.W., 1952, Evaportranspiration in the hydrologic cycle, in The physical basis of water supply and its principal uses, v. 2 of The Physical and Economic Foundation of Natural Resources: U. S. Cong., House Comm. on Interior and Insular Affairs, pp. 25-35. 128

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Evaluation of the Ground-Water Re110urce! of the Paleozoic and Cretaceous Aquifers in the Hill Country ofCentrdl Texa! July 1992 Todd, D. K., 1959b, Annotated bibliography on artificial recharge of ground water through 1954: U.S. Geol. SuiVey Water Supply Paper 14 77. Tucker, D. R., 1962a, Central Texas Lower Cretaceous stratigraphy: Gulf Coast Assoc. Geol. Socs. Trans., v. 12, pp. 839-896. ___ , 1962b, Subsurface Lower Cretaceious stratigraphy, in contributions to the geology of south Texas: South Texas Geological Society, San Antonio, pp. 177-216. U.S. Environmental Protection Agency, 1977a, Report on Medina Lake, Bandera and Medina Counties, Texas: U.S. EPA Working Paper No. 652, 16 p. __ , 19'i'7b, Report on Lake Travis, Burnet and Travis Counties, Texas: U.S. EPA Working Paper No. 664, 18 p. ___ , 1981, Radioactivity in drinking water: U.S. EPA Office of Drinking \Vater, Washington, D.C., 570/9-81-002, 70p. ___ , 1985a, Primary drinking water regulations; synthetic organic chemicals, inorganic chemicals and micro organisms; proposed rule; 40 CFR, pt. 141: Federal Register, v. 50, no. 219, pp. 46936-47022. __ , 1985 b, Protection of public water supplies from ground-water contamination: U. S. EPA Technology Transfer Seminar Publication, EPA/625/4-85/016, 182 p. __ , 1987, Proposed agricultural chemicals in ground water strategic plan: U.S. EPA Office ofT oxic Substances, Washington, D.C. U.S. SuiVey, 1988, Index of surface-water stations in Texas: U.S. Geological SuiVey Open-File report, 88-483, 17 p. U.S. Public Health Service, 1962, Drinking water standards, 1962: U.S. Public Health SeiVice Pub. 956, U.S. Dept. Health, Education, and Welfare, 61 p. U.S. Salinity Laboratory Staff, 1954, Diagnosis and improvement of saline and alkali soils: U.S. Department of Agriculture Handbook 60, 160-p. Walker, l. E., 1979, Occurrence, availability, and chemical quality of ground water in the Edwards Plateau region of Texas: Texas Department ofWater Resources Report 235, 336 p. Webb, W. E., and Hull, A.M., 1962, Engineering geology of Canyon dam, Guadalupe River, Comal County, Texas, Field excursion no. 12, in Geology of the Gulf Coast and central Texas and guidebook of excursions: GeoL Soc. America, 1962 Annual Meeting, Houston, Texas, Houston Geological Society, pp. 385-391. Welder, F. A., and George, W. 0., 1955, Records of test wells at Cattyon ReseiVoir site in Comal County, Texas: U. S. Geological SuiVey open-file rept. Werchan. L. E., Lowther, A. C., and Ramsey, R.N., 1974, Soil suiVey of Travis County Texas; U.S. Department of Agriculture, Soil ConseiVation Service, 123 p. Wermund, E.G., editor, 1974, Environmental units in carbonate terranes as developed from a case study of the sou::hern Edwards Plateau ad adjacent interior coastal plain, in Approaches to environmental geology, a colloquium and workshop: University ofTexas, Bureau of Economic Geology Report, Inv. no. 81, pp. 52-78. Whitney, M.l., 1952, Some zone-marker fossils of the Glen Rose Formation of central Texas: Jour. Paleontology, v. 26, pp. 65-73. 129

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Evaluation of the Ground-Water Resources of the r.. leozoic and Cretaceous Aquifer.• in the Hill Country of Central Texas July 1992 Wilcox, LV., 1948, The quality of water for usc: U.S. Department of Agriculture Technical Bulletin No. 962, 40 p. ___ , 1955, Classifkation and use of irrigation waters: U.S. Department of Agric. Circ. 969, 19 p. \Vilcox, L. V., Blair, G.Y., and Bower, C.A., 1954, Effectofbicarbonate on suitabilityofwater for irrigation: Soil Sci., v. 77, no. 4, p. \Ninslow, A. G., and l
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APPENDIX A Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water (Texas Water Development Board, 1989)

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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Olemkal Constituent or Property (Cllemiaal Symbol) Aluminwn (AI) Antimony (Sb) Anenic (As) AbWKiance, Sources, Ionic Fonn(s) of Occummce and Concentration in Natural and Other Waters AJumimtm, the most abundant metallic element, is the third most abundant element in crustal rocks. Aluminum makes up about eight percent of crustal rocks and is dissolved mainly from silicate igneous rocks and from sedimentary rocks consisting predominantly of sandstones and shales. Some of the many minerals having significant amounts of aluminum are bamdte, spinels, feldspars, and corundum. Industrial Uses and Sources: Manufacture and production ofbuilding materials, various types of vehicles, cans, bottle tops, foils, frozen food trays, light bulbs, power lines, telephone wires, and many other products. Because of its great abundance, aluminum is present in prac:ically all ground waters and surface waters. The predominant form of aluminum in waters having a pH of less than 4.0 is the metallic aluminum cation (AI +3). At pH of about 4.5 to 6.!i a process of polymerization occurs and various simple tocomplexformsofaluminumhydroxide,AI(OH)2,polymeric ions are present in solution. At pH of 7.0 or greater the predominant dissolved form of aluminum in solution is the anion AI (OH)4 -1 (another form of aluminum hydroxide). The latter anion occurs usually in relatively small concentrations of 1.0 mg/1 or less in most natural waters with ground waters having lesser concentrations than surface waters. Water having a pH of 4.0 or less may have several! hundred or several thousand mg/1 of aluminum (AI +3 cation) which usually occur in some springs and in acidic waters from mining operations. Antimony, a non-metallic element with chemical traits similar to arsenic, is relatively rare in crustal rocks. It is most abundant in areas of geothermal geysers and in anti moniallead ores. The most important antimonial minerals, is stibnite. Antimony trioxide (Sb203 ) is soluble in water while antimony trichloride (SbCI3 ) is not. The ionic forms of antimony found in water are 2Sb(OH)2 +1 cation, 2Sb(OH)" -1 anion, and 2Sb (OH)6 +3 cation. [ndustrial Uses and Sources: Manufacture and production of hard and strong lead alloys used in electric cables, batteries, and type printing; compounds of antimony are used in the production of plastics, refrigerators, air conditioners, and aerosol sprays. Surface water may have concentrations of about 0.0004 mg/1 while drinking waters have about 0.014 mg/1. Some mine drailllage waters may have concentrations of 3 to 6 mg/1. Arsenic, .1 non-metallic element, occurs naturally in relatively small arrounts in sulfide ore deposits, commonly forming metal arsenides. The most important arsenic mineral is arsenopyrite. When dissolved in water, its stable ionic forms are arsenate (As +5) and arsenite (As+3) oxy:anions. From pH of3 to 7, the dominant anion is H#4 -1. From pH 7 to 11, the dominant anion is HAs04 -2. The uncharged ion HAs02 (aqueous) occurs under mildly reducing conditions. Industrial Uses and Sources: Manufacture and production of pesticides, paint pigrnen ts, leather, glass, ceramics andl metals. The dissolved concentntion level of arsenic in natural waters rarely exceeds 0.05 mg/i. Concentrations as high as 5 mg/1 have been reported in areas where rocks contain gold ores. A concentration of 40 mg/1 has been reported in geothermal waters. Concentrations as high as 362 mg/1 have been detected in wastewater effiuent from mauufacture of some pesticides. A-I Signifacant, Texas Department of Health ( 1988) Drinking Water Standard Maximwn Constituent Level (MCL) and Method of Removal Aluminum appears to be an essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.3 mg/day which is one (1) percent of the average daily intake of 30 mg/day from food, water and air. However, excessive concentrations may be associated with the cause of neurological disorders; namely Alzheimer's disease (encephalopathies), and mental deterioration due to kidney malfunction (dialysis dementia). Excessive concentrations may also cause adult rickets (osteomalacia) by competing with calcium to leave bones soft and susceptible to fracturing. Aluminum is absorbed gastrointestinally, and about 4 percent of intake by humans is retained causing an accumulation with age. MCL has not been determined. Method of Removal: Distillation, reverse osmosis or ion exchange. Antimony is a non-essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.024 mg/day which is about 3.3 percent ofthe average daily intake ofO. 725 mg/day from food, water and air. Antimony is not considered to be cancer causing. However, excessive concentrations can be toxic to the gastrointestinal tract, heart, respiratory tract, skin and liver. The most adverse impact is on the heart. MCL has not been determined. Method of Removal: Distillation, reverse osmosis or ion exchange. Arsenic is an essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.003 mg/daywhich is about 4.6 percent of the average daily intake of0.065 mg/day from food, water and air. Excessive concentrations of arsenic are poisonous and can cause death, with toxicity varying with form of occurrence. Excessive concentrations can also cause body weight changes, and a decrease in blood hemoglobin as well as promote liver and kidney damage. Primary drinking water standard MCL is 0.05 mg/1. Method ofRemoval: As +3 and As +6 (if present) by reverse osmosis or distillation; As +5 by ion exchange, activated alumina, adsorption, reverse osmosis, or distillation; and organic arsenic complexes by activated carbon.

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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Olemical Constituent or Property (Olemical Symbol) Barium (Ba) Beryllium (Be) Abundance, Sources, Ionic Fonn(s) of Occurrence and Concentration in Natural and Other Waters Barium, an alkaline-earth metallic element, is the sixteenth most abundant element in crustal rocks. It is one of the principal elements in barite a common mineral that occurs in metallic ore veins and in calcite veins in some limestones. Barium is also widely distributed in soils, especially in the wtstern and midwestern U.S. ionic form of barium in water is the cation Ba +2. Industrial Uses and Sources: Manufa< ture and production of drilling muds, pain pigments, glass, motor oil, detergents and magnets, and is used to chemical solutions and as an indicator in x-ray analyses. Median concentrations of barium in most natural waters is approximately 0.045 mg/1, indicating the relatively low solubility of barite in water. High concentrations can be expected in certain oil-field and other brines. Beryllium, a relatively rare alkaline-earth metallic element, occurs most commonly in beryl and bertrandite which are minerals often associated with pegmatites. The ionic forms of beryllium in equilibrium at pH 6.0 are Be +2 cat.ion, BeOH +I cation, (aqueous) and Be(OH)3 -I anion. At pH of about 8.5, the Be +2 cation occurs. Industrial Uses and Sources: Manufaclllre and production of alloys, glass lenses, X-ray tubes, and fluorescent lamps; and is as a refractory in metal smelting and also as an absorber and conductor of heat in satellites, missiles, rockets and laser technology. Concentrations ofberyllium in water are usually very small and usually less than the detection limit of0.003 mg/1, owing to its low equiltbrium solubilities. Concentrations of 1.0 mg/1 or more mar be regularly detected in acidic (low pl-1) waters associate< I with some mining SignifiCallt, Texas Department of Health ( 1988) Drinking Water Standard Maximum Constituent Level (MCL) and Method of Removal Barium is a non-essential element for human metabolic needs. The average daily intake by an adult human from drinking watersisabout0.083mg/daywhich is 10 percent of the average dailyintakeofabout0.830mg/dayfrom food, water and air. Its distribution is primarily to bones, and some studies have linked it to elevated blood pressure. Barium is known to contribute to the hardness of water (see Primary drinking water standard MCL is 1.0 mg/1. Method of Removal: Ion exchange, reverse osmosis or distillation. Beryllium is a non-essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.001 mg/day which is 8.3 percent of the average daily intake of about 0.012 mg/day from food, water and air. Its adverse effects on humans are unclear. However, some studies have linked it with decreases in growth rate. MCL has not been determined. Method of Removal: Distillation, reverse osmosis or ion exchange. r-------------r----------------------------------------------------1---------------------------------------------------__, Boron (B) Boron, a non-metallic clement, is relatively rare in crustal rocks, but is widely distributed as onhoboric acid (H3B01 and H2B01-l anion) in volcanic regions, and in evaporites (borates) in some ar1 d lake regions. The most i rnportan t boron corn pound is borax which is from the minerals colemanite and kernite which an: readily obtained from brine lakes in southern California. Industrial Uses and Sources: Wood and fabric processing; and manufacture and production of detergent'>, glassware, leather, carpels, cosmetics, photographic supplies, water and and jet fuels. Boron is a minor constituent of most natural waters with concentrations up to onlyafewtenthsofa rng/1. It is found in oil-field brines and the remains of some plants and animals. High concentrations are found in thermal springs in some volcanic areas where concentrations of 48 to 660 mg/1 have been detected. Ocean water has a concentration of about 4.6 mg/1. Relatively high concentrations may be present in sewage and industrial waste effluent. A-2 Boron in proper form and may be vital to human calcium metabolism (see calcium) to help prevent bone deterioration (osteoporosis), and vital to human copper metabolism (see copper) to help main a healthy cardiovascular system. Appropriate daily boron intake by humans has been reported to range from I to 3 rng/day from food, water and supplements. The specific intake limit from drinking water is unknown. Excessive amounts greater than 3 rng/day taken orally from food, water and supplements may be dangerous; adversely effecting human calcium and copper metabolisms. Another investigation ofboron indicated that under conditions of low dietary magnesium, dietary boron may influence the brain function of healthy adult men and women. Boron in small concentrations is essential for plant growth. However, high excessive concentrations in soils and irrigation waters are harmful to plants; depending on the type of plant and the concentration of boron. Concentrations as high as 1.0 mg/1 are permissible for irrigation of sensitive crops such as fruit trees (lemon, orange, peach, etc.), nut trees (pecans, etc.) and navy beans. Concentrations as high as 2.0 mg/1 are permissible on semi-tolerant crops such as most grains, cotton, potatoes, and some other vegetables. Concentrations as high as 3.0 rng/ I are permissible on tolerant crops such as alfalfa, and most root vegetables. The most serious hazard posed by boron to the environment (air and perhaps water) is through boranes which are highly toxic compounds used as fuels for rocket rnotorsandjetengines. MCL has not been determined. Method of Removal: Distillation, reverse osmosis or ion exchange.

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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related of Water , fireworks, flares, incendiary bombs, medicines, and protective coatings. Calcium and sodium are usually the dominant cations in natural water&. Magnesium is not a dominant cation in most natural waters because its chemical behavior is very different from that of calcium and sodium. Consequently, in most natural waters, the magnesium concentration is much lower than the calcium or sodium. Calcium and magnesium are found in large quantities in some brines. Magnesium is present in large quantities in sea water with concentrations exceeding 1,000 mg/1. A-3 Signifacant, Texas Department of Health (1988) Drinking Water Standard Maximwn Constituent Level (MO.) and Method of Removal The beneficial or hazardous significance of bromide concentrations in waters used for drinking, industrial or irrigation purposes is unknown. The presence of small amounts of bromide in fresh water probably is not of any ecologic significance. The introduction of bromine to the environment by human activities in urban areas is probably significant. MCL has not been determined. Method of Removal: Distillation, reverse osmosis or ion exchange. Cadmium is a non-essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.001 mg/day which is 2.9 percent of the average daily intake of0.035 mg/day from food, water and air. Excessive concentrations in water accumulate in the kidney and liver and may cause kidney damage and abnormal presence of protein, sugar and amino acid in the urine. Cadmium is also known to cause lung and prostate cancer when inhaled. Primary drinking water standard MCL is 0.01 mg/1. This concentration is also the upper limit for irrigation waters, because cadmium is known to accumulate in and be toxic to plants. Method of Removal: Distillation, reverse osmosis or ion exchange. Calcium and magnesium are essential elements for human metabolic needs and for plant nutrition. Drinking waters account for about 25 percent of the average daily intake of calcium by an adult human and for about 3 percent of the average daily intake of magnesium by an adult human. A deficiency of calcium may result in bone deterioration (osteoporosis) while an excess may cause kidney stones. A deficiency of magnesium may result in an electrolyte imbalance, while an excess may cause muscle weakness. High concentrations of magnesium have a laxative effect, especially on new users of the water supply. Calcium and magnesium combine with carbonate, bicarbonate, sulfate, and silica to form heat-retarding, pipeclogging scale in boilers, water heaters, cooking utensils, and other hot water using appliances and heating utensils, and other hot, water using appliances and heating exchange equipment. Calcium and magnesium are soap consuming (see hardness as CaC03}. Low concentrations arc desirable for electroplating, tanning, dyeing, and textile manufacturing. Method of Removal: Distillation, reverse osmosis or ion exchange.

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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water
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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Otemical Constituent or Property (Otemical Symbol) Copper (Cu) Cyanide (CN) Fluoride (F) Gro68Alpha Abwldance, Sources, Ionic Fonn(s) of Occurrence and Concentration in Natural and Other Waters Copper, a moderately abundant metallic element, occurs in crustal rocks as free native metal, and in such copper minerals as chalcocite, bornite, cuprite, malachite, and azurite. Copper form' rather stable sulfide ore minerals, which also sometimes contain iron. Coppercommonlyoccursin waterasCu +2orCu + 1 cation forms. Above pH 7.0, the dominant form may be the anion -1. Aerated water with carbon dioxide may have (aqueous) as the dominant uncharged ion. Industrial Uses and Sources: Manufacture and production of various types of wire, superconductors, electroplating solutions, electronic and electrical parts, chemical etching solutions, pesticides and many other products. Copper may be present in conc•::ntrations as great as a few hundred mg/1 in acidic (low pH) drainage waters from copper mines. Natural waters usually contain less than 0.01 mg/1. Cyanide is a synthetic organic substance commercially made on a large scale by reacting methane gas (CH1 ) with the ammonium cation (NH4 + 1) to form hydrogen cyanide (HCN) which occurs as a liquid at 25.6C and readily hydrolyzes in water. The ionic form of cyanide is the CN -1 anion which form' stable complex compounds with most metals. Industrial Uses and Sources: Production of methyl methacrylate, acidic acid, nylon, gold from gold ores, and fertilizers. The average conc•entration in drinking water has been determined to be 0.00009 mg/1. Fluorine, a moderately abundant non-metallic halogen group element, is present in waters as the anion fluoride (F -I). It is dissolved in small to very small quantities from such minerals as fluorite, amphiboles, apatite, and mica. Fluoride minerals are most commonly found in carbonate rocks, volcanic rocks or sedimentary rocks derived from volcanic rocks. Industrial Uses and Sources: Manufacture and production of glass, steel, aluminum, pesticides, and fertilizers, and used in electroplating. Comentrations of fluoride in natural waters generally do not exceed 10 mg/1 in ground waters or 1.0 mg/1 in surface waters. The concentration of fluoride may be as much as 1,600 mg/1 in some brines. Fluoride is added to many public drinking waters by fluoridation. Alpha radiation consists of the emission of positively charged helium nuclei from the nucleus of atoms having high molecular weight. When an alpha particle is emitted from an atom, the atomic weight of the atom decreases by four ( 4) units. This is called radioactive decay or disintegration and is measured and reported in water analyses as gross alpha in picocuries per liter (pCi/1). Alpha-emitting isotopes in natural waters are mainly isotopes of radium and radon (see radium and radon) which are members of the uranium and thorium disintegration ( A-5 Signifacant, Texas Department of Health ( 1988) Drinking Water Standard Maximwn Constituent Level (MCL) and Method of Removal Copper is an essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.2 mg/ day which is 12 percent of the average daily intake of 1. 7 mg/ day from food, water and air. A deficiency may result in anemia, loss of pigment in the skin, reduced growth and loss of arterial elasticity. Toxicity may include Wilson's disease (damage to the brain, eyes, kidney, and liver) for susceptible persons, and disorder (hepatic cirrhosis). Secondary drinking water standard MCL is 1.0 mg/1. Method of Removal: Ion exchange, reverse osmosis or distillation. Cyanide is a non-essential constituent for human metabolic needs. The average daily intake by an adult human has been estimated to be 0.00009 mg/1. Free compounds of cyanide are readily absorbed through the gastrointestinal tract and lung. Cyanide is distributed to the blood, lung, liver and kidney. Excessive concentrations in water may result in hyperventilation, vomiting, unconsciousness, convulsions, rapid and irregular heart rate, vascular collapse and death. EPA's "no observed adverse effect levels" for various cyanide compounds are given on page 237 ofLappenbusch, 1988, and range from 0.020 mg/ I for hydrogen cyanide to 0.200 mg/1 for phosphorus-silver cyanide. Method ofRemoval: Alkaline chlorination, electrolytic decomposition, ozone oxidation or ion exchange. Fluoride is an essential constituent for human metabolic needs. The estimated average daily intake of fluoride by an adult human is about 1.7 mg/day from food, water, and air. About one-half (0.85 mg/day) of this is probably from drinking waters. Fluoride concentrations between 0.6 and 1.7 mg/1 in drinking water have a beneficial effect on the structure and resistance to decay of children's teeth. A deficiency may result in weakening of bone (osteoporosis). Certain but unknown concentrations of unusually high fluoride may be beneficial for the prevention of hardening of the arteries. Excessive fluoride may cause mottling of teeth and abnormal bone thickening and hardening (osteosclerosis) depending on the concentration, age ofthe individual, amount of water ingested, and susceptibility of the individual. Primary drinking water standard MCL is 4.0 mg/1. Secondary drinking water standard MCL is 2.0 mg/1. Method of Removal: Distillation, reverse osmosis, ion exchange or lime softening. The release of energy from an atom of a radioactive substance is called ionizing radiation. Alpha particles which are subatomic particles and one of the forms ofionizing radiation are relatively slow-moving, but carry a strong positive charge with energy levels so high that when they collide with an atom or molecule of other substances, they strip away an electron; thus altering or ionizing the substance. Alpha particle radiation cannot penetrate a piece of paper or human skin, but is very dangerous when the radioactive substance emitting them is contained in (m11timlt'fi lll'xlpagr)

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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water much as 50 to 75 pCi/1. Beta radiation consists of the emission ofhigh energy electrons or positrons from the nucleus of atoms having high molecular weight. Dudng the production of a beta particle, the neutron of the atom is converted to a proton and an electron is emitted as the beta particle. When a bet.-. particle is emitted from an atom, the atomic number of the atom increases one (1) unit. This beta particle decay or disintegration is measured and reported in water analyses as gross beta in picocuries per liter ( pCi/1). Natural beta-emitting isotopes are those in the urani urn and thorium disintegration series, and also from potassium-40 and rubidium-87. Strong beta emitting isotopes from nuclear fission which are important in water chemistry are strontium-89, strontium-90, iodine-131, phosphorm.-32 and cobalt-60. High gross beta concentrations greater than 50 pCi/1 have been detected in ground waters from the Gulf Coast aquifer in southeastern Texas. Stable (non-radioactive) iodine, a relatively rare non-metallic halogen group element, is present in water as the iodide anion (I -1) and iodate anion (103 -1). These forms are widely distributed. with their circulation being strongly influenced by plant absorption. Calcium and sodium iodate salts which are known toot:curin (sodium nitrate) deposits may be important sources ofiodine concentrations in some ground waters. Industrial Uses and Sources: Iodine is used in chemical analyses, while iodine compounds are used in making photographic film, antiseptics and as an additive to table salt. Concentrations in natural watfTs probably rarely exceed 0.04 mg/1, while sea water has about 0.06 mg/1 and some brines contain as much as 50 mg/1. Iron is the !;econd most abundant metallic element in crustal rocks. Iron is present in numerous igneous rock minerals, and is usually reprecipitated quickly after being released by weathering, commonly forming cement in sedimentary rocks. The most important iron ore minerals are hematite, geothitelimonite, magnetite and siderite. Industrial Uses and Sources: Production of steel for a wide variety of products related mainly to transportation, shipping, and construction, (co11limll'd unci /JaW) A-6 Significant, Texa& Department of Health (1988) Drinking Water Standard Maximwn Con.tituent l...ewel (MCL) and Metbocl of Removal ingested water and food or in inhaled air. Therefore, alpha particles emitting from radioactive substances ingested or inhaled are most harmful to living tissues of human internal organs by altering or destroying the atoms and molecules of such tissues. The amount of alteration or destruction of the tissues depends on where and how long the tissues were exposed to the radiation and the dosage of the radiation. Under these varying circumstances and conditions, the organ having the effected tissue may repair itself of the damage or may develop cancerous cells and tumors. In some instances, certain ionizing radiation is used to advantage by pinpointing certain cancers in human tissue, bombarding them with heavy ion radiation, destroying them and prolonging life. The primary drinking water standard MCL for gross alpha radiation is 15 pCi/1. Method ofRemoval: By the methods used to remove the radioactive substance emitting the radiation (see "Method of Removal" for radium, radon, and uranium). The release of energy from an atom of a radioactive substance is called ionizing radiation. Beta particles which are subatomic particles and one of the formsofionizing radiation are extremely fast-moving electrons (negatively charged) and positrons (positively charged) which have extremely high energy levels. When beta particles collide with an atom or molecule of other substances they alter or ionize the substance. Beta particle radiation is capable ofpenetratingseveral millimetersofhuman skin, and like alpha particle radiation, it can be harmful when emitted inside the human body (see corresponding paragraph or alpha particle radiation). Positrons emitted as beta particles can combine with free electrons to produce gamma ray radiation which has great penetrating power and is capable of passing easily imo the human body causing damage to tissue in the process. The primary drinking standard MCL for gross beta radiation is 50 pCi/1;. Method ofRemoval: By the methods used to remove the radioactive substance emitting the radiation (see "Method of Removal" for radium, radon, and thorium). Iodine is an essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is about 0.010 mg/ day from food, water and air. A deficiency may result in an enlarged thyroid gland (goiter). However, excessive concentrations may cause goiter and overactivity of the thyroid gland (hypothyroidism). MCL has not been determined. Method of Removal: Activated carbon. Iron is an essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is 0.6 mg/day which is only 3 percent of the average daily intake of 20 mg/ day from food, water and air. A deficiency of iron in the body may result in iron deficiency anemia (a hypochromic anemia). Intake of excessive concentrations may cause gastrointestinal irrigation. Oral intake of highly excessive concentrations of iron are known to cause iron deposition in (COIIIimml llntl pagr)

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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Olemical Constituent or Property (
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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Otemical Constituent or Property (Otemical Symbol) Manganese (Mn) ( rontinual) Mercury (Hg) Molybdenwn (Mo) Nickel (Ni) Nitrate (NO,) or Nitrate as Nitrogen (N) Abundance, Sources, Ionic Fonn(s) of Occurrence and Concentration in Natural and Other Waters Industrial Uses and Sources: Manufacture and production of alloys, batteries, paint, glass, flares and fireworks. Concentrations of manganese in natural waters are usually small, with exceptions above 1.0 mg/1 occurring around some thermal springs and in brines. Mercury, a metallic element, and mercury ore (the mineral cinnabar) are rare in crustal rocks and not widely dispersed. The most common ionic form of mercuty in ground water is the cation Hg +2. It also can occur as the complex organic cation HgCH5 +1 (methyl mercury). Industrial Uses and Sources: Manufacture and production of organic pesticides, explosives, batteries, photographic supplies, scientific instruments, paints, pharmaceuticals, paper and pulp, and catalysts. Mercury compounds are emitted during the combustion of coal and oil. of mercury in natural waters are usually less than mg/1, with exceptions occurring near cinnabar mines and around industrial sites where the element is used for various purposes. Molybden Lim is a relatively rare transition metallic element found most commonly in the minerals molybdenite and wulfenite. In oxidizing environments, the dominant ionic form of molybdt:num is Mo +6.1n waters having a pH greater than 5.0 the dominant form is the anion Mo01 -2. Industrial Uses and Sources: Manufacture and production of alloys, wire, lubricant-;, electrical parts, fire proofing fabrics. and in the dyeing of silk and wool. Most natural waters cuntain less than 0.001 mg;l. Concentrations as much as 3.8 mg/1 have been detected in waters effected by molybdenum mining operations. 1\ickel is a relatively rare transition metallic element in crustal rocks that sometimes substitutes for iron in ferromagnesian igneous-rock minerals, and which tends to precipitate with iron and oxides. Nickel is mined witlh ferrous sulfide ores and nickel-bearing ores developed on ultramafic bedrock, terrances. l mportan t nickel-bearing minerals include niccolite, millerite, pentlandite and garnierite. The iionic forms of nickel in ground water are the cations Ni +2, Ni +3, and Ni +4. Industrial Uses and Sources: Manufactun: and production of alloys, scientific instruments, pendulums, steel tapes, coins, electrical parts, propellers, acid pumps, valves and plated metals. A median •:oncentration of 0.01 mg/1 is estimated for natural waters. Concentrations of about 0.04 mg/1 have been detected in waters in some mineralized regions. The main source for the occurrence of nitrogen in ground water are decaying organic matter, human and animal wastes, fertilizers, and the minerals soda niter (sodium nitrate) and niter (potassium nitrate) found in rocks and soils. Nitrogen ionic forms that occur in ground water are the anions N05 -2 (nitrate), and N02 -2 (nitrite) and the cation NH4 +1 (ammonium). The nitrate anion (N05 -2) is the ionic form most commonly detected in ground water. The nittrite and ammonium ions are generally unstable in ground water and are usually not detectable. Another nitrogen ionic form is the cyanide anion CN -1 (see cyanide) which may be found in ground water contaminated by some wastewater eilluents. Concentrations of (coutimud 11nct A-8 Signif"ICallt, Depanment of Health (1988) Drinking Water Standard Maximwn eon.tituent l..eftl (MCL) and Method of Removal Mercury is a non-essential element for human metabolic needs. The average daily intake by an adult human from drinking waters is only 0.002 mg/day which is about 30 percent of the average daily intake from food, water and air. Any measurable concentration from drinking water is undesirable. Adverse effects from excessive concentrations of mercury may include kidney damage and abnormal presence of protein in the urine. Also, ethyl mercury, adversely affects the nervous system. Primary drinking water standard MCL is0.002 mg/1. Method ofRemoval: Reverse osmosis or distillation. Molybdenum is an essential element for human metabolic needs. The average daily intake by an adult human from drinkingwatersisabout0.011 mg/daywhich isabout3percent of the average daily intake of0.35 mg/ day from food, water and air. A deficiency may result in reduced quantities of metallo enzymes.Adverse effects from excessive concentrations include liver, kidney, spleen, and adrenal damage. At some natural, excessive concentrations, toxicity may include elevated uric acid resulting in gout and bone and joint deformities. MCL has not been determined. Method of Removal: Ion exchange, reverse osmosis or distillation. The import."lnce of nickel for human metabolic needs is unknown. The average daily intake by an adult human from drinking waters is not specifically known, but the average daily intake is about 0.34 mg/ day from food, water, and air. Toxicity may include gastrointestinal irrigation and an inflammation of the skin (dermatitis). Nickel is cancer causing when inhaled but not when ingested. MCL has not been determined. Method of Removal: Ion exchange, reverse osmosis or distillation. Nitrate is a non-essential constituent for human metabolic needs. The average daily intake by an adult human from drinking waters is about 20 mg/day which is about 13 percent of the average daily intake from food, water and air. Nitrate concentrations in water which are significantly greater than the local average may suggest pollution. Water having excessively high nitrate concentration have been reported to be the cause of methemoglobinemia (an often fatal disease in infants); therefore such water should not be used for infant feeding. Excessive concentrations of nitrate may be a cancer precursor. Nitrate is helpful in reducing intercrystaline cracking of boiler steel. It encourages growth of algae and other organisms which (conti111tM nnct

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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water
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Abmtdance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Olemical Constituent or Property (Oaemical Symbol) Radon (Rn) Selenium (Se) Abundance, Ionic Fonn(•) of Occurrence and Concentration in Natural and Other Waters Radon, a strongly radioactive, alpha-emitting noble gas, is a product of the disintegration of radium i;sotopes 223,224, and 226. Radon-222 produced from the decay of radium-226 has a 3.8 day half-life and is the only radon isotope of importance in the water environment because the other radon isotopes have very shmt half-lives of less than a minute. Radon-222 decays through aseriesofotherisotopes to 0. In water analyses, radon-222 concentrations are measured and reported in per liter (pCi/1). The detection ofradon-222 is best obtained by immediate analysis, of its short half-life, and solution to the atmosphere. Radon commonly occurs in ground waters in areas having significant concentrations of radium in igneous rocks, uranium ore bodies, clastic sedimentary rocks such as certain shales and sandstones, and volcanic tuffs. Investigations have found that ground"' aters of the Ogallala aquifer in part of the Texas High Plains had radon concentrations ofaboutlOO to 1,000 pCi/1, that the ground waters of the Hickory aquifer around the Llano uplift of central Texas had radon concentrations ofless than IOC pCi/1 and up to 1,400 pCi/1, and that radon concentrations in the ground waters of the Gulf Coast aquifer in the Houston area ranged from undetectable amounts to as much as :J,300 pCi/1. Selenium is a rare non-metallic which is widely distributed in sediments in very small amounts and is chemically similar to sulfur. In the presence of iron, selenium is co precipitated with the mineral pyrite. One selenium mineral, ferrosclitt:, may be associated with uranium ore deposits. Selenium is found in oxidizing solutions as the anions 2, and ScO,, -2. These anions are unstable and are readily reduced 10 insoluble selenium Se02 and compounds. Industrial Uses and Sources: Manufacturoe and production of photoelectric cells, television cameras, copying machines, solar batteries and rectifiers, colored glass and ceramics, and hard rubber. Its aqueous mobility is limited by geochemical controls,
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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water
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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Olemkal Constituent or Property (r its resistance to corrosion. Titanium is very insoluble in w:1ter, consequently concentrations in natural waters are very low. Only the cation Ti +4 should be expected in nautral waters. Analyses of titanium in some natural waters for public supply had concentrations of less than O.OOI5 mg/1. Analyses of acidic (low pH) meters and some brines have detected concentrations of more thc,n I.O mg/1. A-12 Signif"JCaDt, Tex. Department of Health (1988) Drinking Water Standard Maximwn Constituent LewJ (MO.) and Method of Removal Sulfate is a non-essential constituent for human metabolic needs. The average daily intake of sulfur by an adult human from drinking water is about 9.2 mg/day. Any high concentration in drinking water is undesirable. Water containing about 500 mg/1 sulfate tastes bitter. Excessively high concentrations of sulfate in water causes inflammation of the stomach and intestines (gastroenteritis), producing such symptoms as diarrhea, abdominal cramps, nausea, vomiting, and fever, especially in infants and children. Secondarydrinking water standard MCL is 300 mg/1. Method of Removal: Distillation, reverse osmosis or ion exchange. Thorium is not known to be an essential element for human metabolic needs. The known impact of thorium in water quality is related to the toxicity from its radioactive disintegration products such as radium-228 (see radium) and its beta particle emissions (see gross beta). MCL has not been determined. Method ofRemoval: Distillation, reverse osmosis or ion exchange. The beneficial or hazardous significance of titanium concentrations in waters used for drinking, industrial or irrigation purposes is unknown. MCL has not been determined.MethodofRemovai:Distillation,reverseosmosis or ion exchange.

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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water . The dominant ionic forms of vanadium in ground water are V +5 anionic complexes with oxide and hydwxide. Industrial Uses and Sources: Manufacture and production of special steels for locomotive, automobile, and truck cylinders, pistons and bushings, and for high speed tools and die blocks; and also used as a catalyst. Alloys of vanadium are very rust and corrm.ion resistant. Its aqueous geochemistry is rather complicated, and fairly high solubility can be expected in oxidizing alkaline environ men to; around ore bodies. However, natur<1l waters rarely have concentrations greater than 0.01 mg/1. Concentration of a few tenths. of a mg/1 have been detected in acidic (low pH) waters from thermal springs. Zinc is. a moderately abundant metallic element in crustal rocks, occurring in such minerals as sphalerite, zincite, franklinite, smithsonite, willemite and hemimorphite. The ionic form of zinc in ground water is the cation Zn +2. Industrial Uses and Sources: Used widely in galvanizing, electroplating and metallurgy, and in the manufacturte and production of paints, rubber, cosmeti.cs, plastics, soap, paper, and >ynthetic fibers. Natural waters have a median concentration of0.02 mg/1. Waters effected by mine drainage commonly contain 0.1 mg/1 or more of zinc. Dissolved solids (OS) are the apprOJ
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Abundance, Sources, Form of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Prop_ertles of Water 01emical Conlltituent or Property ( follows by using me/1: %Na = Na(100) (Na+K+Mg+Ca) Signif"acant, TeXM Department of Heald! (1988) Drinking Water Standard Maximwn Conlltituent Lewl (MQ.) and Method of Removal Water low in hardness causes corrosion of metallic surfaces. Hard water consumes excessive amounts of soap, and causes the deposit of soap curd on bathtubs. Hard water forms scale in boilers, water heaters, hot water using appliances and pipes. Hardness equivalent to COs and HCOs is called carbonate hardness. Any hardness in excess of this is called non-carbonate hardness. A carbonate hardness value of less than 100 mg/1 is considered desirable for domestic use. MCL has not been determined. Method of Removal: Distillation, reverse osmosis and ion exchange. Conductivity is a measure of the electrical conductivity of water and varies with the amount of dissolved solids in the water. MCL has not been determined. The conductivity of water is used to determine the salinity hazard of irrigation waters. A conductivity of 2,250 micromhos/cm probably represents the upper limit of salinity that should be considered as being safe for use of the water for supplemental irrigation. A pH of7.0 indicates the neutrality of a solution. Values of pH higher than 7.0 denote increasing alkalinity, while values of pH lower than 7.0 indicate increasing acidity. The pH is a measure of the activity of the hydrogen ions in solution. It may be expressed using hydrogen ion (H +1) concentration rather than the activity. The corrosiveness of water generally increases with decreasing pH. However, excessively alkaline waters with very high pH may also attack metals. Secondary drinking water standard is 7.0 or greater. Percent sodium is the ratio of the sodium ions to total cations times 100. A sodium percentage exceeding 60 percent is a warning of a sodium hazard. Continued irrigation with this type of water will impair the tilth and permeability of the soi I. Sodium Adsorption Ratio (SAR) Residual Sodium Carbonate (RSC) An indicator of the sodium hazard of irrigation waters. Calculatcd as follows using me/1: SAR = Na/ v (Ca + Mg/2 An indicator of the sodium hazard of irrigation waters. Calculated as follows using me/1: RSC = (C03+HC03 ) (Ca+Mg) or RSC = 0.02 (Total AlkalinityHardness) A-14 The SARis the ratio for soil extracts and irrigation waters used to express the relative activity of sodium ions in exchange 1eactions with the soil. An SAR of 14 is probably the upper limit for waters that can be safely used for supplemental irrigation. As calcium and magnesium precipitates as carbonates in the soil, the relative proportion of sodium in the water is increased. Waters having 1.25 to 2.50 me/1 ofRSC are probably marginal for irrigation use, and those having greater than 2.50 me/1 RSC probably are not suited for irrigation.

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Abundance, Sources, Fonn of Occurrence, Concentration, Significance, Maximum Constituent Level and Method of Removal for Selected Dissolved Chemical Constituents and Related Properties of Water Cltemical Constituent or Property (Cltemical Symbol) References Abundance, Sources, Ionic Fonn(s) of Occurrence and Concentration in Natural and Other Waters SignifiCallt, TexM Depanment of Healch (1988) Drinking Water Standard Maximwn Constituent U\rel (MO.) and Method of Removal Cech,l., et at., 1988, Radon distribution in domestic water ofTexas: Ground Water, Vol. 26, No.5, pp. 561-569. Cobb, C. E., 1989, Living with radiation: National Geographic, Vol. 175, No. 4 (April 1989), pp. 403-437. Cooley, D. G. (Editor), 1973, Family medical guide: Better Homes and Gardens Books Published by Meredith Corp., New York, New York. Hem,J. D., 1985, Study and interpretation of the chemical characteristics of natural water: U.S. Geological Survey Water-Supply Paper2254, 263 P Hurlbut, C. S.,Jr., 1971, Dana's manual of mineralogy: John Wiley & Sons, Inc., New York, New York, 579 p. Kraus, E. H., Hunt, W. F. and Ramsdell, L. S., 1951, Mineralogy: McGraw-Hill Book Co., Inc., New York, New York, 664 p. Lappen busch, W. L. 1988, Contaminated waste sites, property and your health: Lappen busch Environmental Health, Inc., Alexandria, Virginia. Lyerly, P.J. and Longnecker, D. E., 1962, Salinity control in irrigation agriculture: Texas Agricultural Experiment Station Bulletin 876, Texas A & M University. Nebergall, W. H Schmidt, F. C. and Holtzclaw, H. F.,Jr., 1968, College chemistry with qualitative analysis: Raytheon Education Company, Boston, Mass., 760p. Nielsen, F. H., 1989, Effect of boron depletion and repletion on calcium and copper status indices in humans fed a magnesium-low diet: U.S. Department of Agriculture Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, N. D. (Abstract from the FASEBJournal p. A760, 1989) and Article titled, Belief in Boron: An element of strength: Science News, Vol. 135, p. 204, April1989. Nordstrom, P. L., 1988, Occurrence and quality of ground water in jack County, Texas: Texas Water Development Board Report 308, 87 p. Pen land,J. F., 1989, Effects oflow dietary boron (B) and magnesium (Mg) on the brain function ofhealthy adulL": U.S. Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, N.D. (Abstract from the FASEB.Journal3-4: p. Al242, 1989). The World Book Encyclopedia, 1984-1989, World Book Inc., Chicago, Illinois. Texas Department ofHealth, 1988, Drinking water standards governing drinking water quality and reporting requirements for public water supply systems: Texas Department of Health, Division of Water Hygiene. Texas Water Development Board, 1989, Source, significance, and methods for removal of dissolved minerals: Form 890018 (Revised March, 1989), 2 p. U.S. Salinit} Laboratory Staff, 1954, Diagnosis and improvement of saline and alkali soils: U.S. Department of Agriculture Handbook 60, 160 P Wilcox, L. V, 1948, Tbe quality of water for irrigation use: U.S. Department of Agriculture Technical Bulletin No. 962, 40 p. Wilocx, L. V, 1955, Chs..'>ification and usc of irrigation waters:. U. S. Department of Agriculture Circular No. 969, 19 p. Note: This table was reuiewed by personnel of the Division of Water Hygiene of the Texas Department of Health (june 1989). A-15

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APPENDIXB Water Quality Summaries for the Paleozoic and Cretaceous Aquifers

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The following tables provide water-quality summaries for the named aquifers. Aquifer: Hickory. Approximate Nwnberof Constituent Percent Distribution MCL Concentrations in Study Area Exceed Exceed Constituent (mg/1) Made Range (mg/1) Average (mg/1) Average MCL Nitrate 44.3 35 <0.4 to 111 7.6 20 3 Fluoride 4.0 37 0.2 to 2.4 0.8 22 0 Fluoride 2.0 37 0.2 to 2.4 0.8 22 3 Chloride 300 48 10 to 653 83 31 4 Sulfate 300 48 7 to 267 55 31 0 Dissolved 1,000 45 320 to 1,610 554 36 8 Solids Sodium 20 42 7 to 240 60 38 62 Hardness as None 41 120 to 690 369 51 CaC03 Aquifer: Mid-Cambrian Approximate Nwnberof Constituent Percent Distribution MCL Concentrations in Study Area Exceed Exceed Constituent (mg/1) Made Range (mg/1) Average (mg/1) Average MCL Nitrate 43.3 31 <0.4 to 265 23.9 26 10 Fluoride 4.0 10 0.4 to 4.0 1.4 20 0 Fluoride 2.0 10 0.4 to 4.0 1.4 20 20 Chl01ide 300 33 7 to 378 50 27 3 Sulfate 300 33 7 to 103 30 24 0 Dissolved Solids 1,000 32 240 to 966 491 41 0 Sodium 20 28 1 to 320 46 29 46 Hardness as None 29 108 to 634 369 55 CaC03 Aquifer: Ellenburger-San Saba Approximate Nwnberof Constituent Percent Distribution MCL Analyses Concentrations in Study Area Exceed Exceed Constituent Made Range (mg/1) Average (mg/1) Average MCL Nitrate 43.3 37 <0.4 to 56 11.8 32 5 Fluoride 4.0 38 0.1 to 1.7 0.5 45 0 Fluoride 2.0 38 0.1 to 1.7 0.5 45 0 Chl01ide 300 50 9 to 122 38 34 0 Sulfate 300 50 8 to 91 35 42 0 Dissolved 1,000 38 317 to 718 452 47 0 Solids Sodium 20 37 6 to 61 24 41 Hardness as None 50 260 to 626 384 40 CaC03 B-1

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Marble FalbJ Approximate Nwnberof Constituent Percent Dimibution MCI. Analyses Concentrations in Study Area Exceed Exceed nstituent ( /1) Made e( I) Ave ( I) e MCI. Nitrate 44.3 11 1.8 to 705 131 18 27 Fluoride 4.0 4 0.1 to 0.4 0.2 25 0 Fluoride 2.0 4 0.1 to 0.4 0.2 25 0 Chloride 300 16 15 to 167 53 25 0 Sulfate 300 15 11 to 136 30 27 0 Dissolved 1,000 12 339 to 1,560 580 17 17 Solids Sodium 20 10 2 to80 21 40 50 Hardness as None 15 252 to 1,120 459 27 CaC03 Aquifer: Lower Trinity Approximate Nwnberof Constituent Percent Distribution MCI. Analyses Concentrations in Study Area Exceed Exceed (mg/1) Made Range (mg/1) Average (mg/1) Average MCI. Nitrate 44.3 88 <0.4 to 69 4.3 24 2 Fluoride 4.0 95 0.0 to 5.3 1.8 39 8 Fluoride 2.0 95 0.0 to 5.3 1.8 39 34 Chloride 300 94 11 to 2,440 173 18 13 Sulfate 300 94 15 to 1,790 265 33 31 Dissolved 1,000 95 239 to 4,663 969 35 35 Solids Sodium 20 91 6 to 1,500 183 35 80 Hardness as None 87 61 to 1,920 373 34 CaC03 Aquifer: Middle Trinity Approximate Nwnberof Constituent Percent Distribution MCI. Analyses Concentrations in Study Area Exceed Exceed Constituent (mg/1) Made Range (mg/1) Average (mg/1) Average MCL Nitrate 44.3 249 <0.4 to 155 6.3 17 3 Fluoride 4.0 264 0.0 to 7.0 B-3 1.5 39 7 Fluoride 2.0 264 0.0 to 7.0 1.5 39 25 Chloride 300 277 4 to 620 46 23 2 Sulfate 300 281 2 to 3,360 252 22 20 Dissolved 1,000 266 179 to 5,690 704 28 15 Solids Sodium 20 271 2 to 1,020 49 27 52 Hardness as None 284 91 to 3,060 545 24 CaC03 B-2

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Aquifer: Upper Trinity Approximate Number of Constituent Percent Distribution MCL Analyses Concentrations in Study Area Exceed Exceed Constituent (mg/1) Made Range (mg/1) Average (mg/1) Average MCL Nitrate 44.3 135 <0.4 to 88 5.1 24 2 Fluoride 4.0 128 0.0 to 5.5 1.4 35 6 Fluoride 2.0 128 0.0 to 5.5 1.4 35 28 Chloride 300 148 2 to 640 27 18 <1 Sulfate 300 149 4 to 2,370 360 26 26 Dissolved 1,000 139 227 to 4,758 860 25 20 Solids Sodium 20 140 4 to 1,050 26 20 24 Hardness as None 145 206 to 2,460 680 27 CaC03 Aquifer: Edwards Plateau Approximate Number of Constituent Percent Distribution MCL Analyses Concentrations in Study Area Exceed Exceed Constituent (mg/1) Made Range (mg/1) Average (mg/1) Average MCL Nitrate 43.3 105 <04 to 384 19.0 23 10 Fluoride 4.0 100 0.0 to 0.8 0.3 22 0 Fluoride 2.0 100 0.0 to 0.8 0.3 22 0 Chloride 300 108 2 to 256 33 32 0 Sulfate 300 106 <4 to 130 14 30 0 Dissolved 1,000 105 105 to 1,310 357 34 1 Solids Sodium 20 105 <1 to 150 20 32 32 Hardness as None 108 101 to 539 295 49 CaC03 B-3

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APPENDIX C Distribution of Nitrate, Fluoride and Sulfate Concentrations by Range in Concentration Categories, Averages and Medians for the Paleozoic and Cretaceous Aquifers Appendix C-l .....•.......... Nitrate Appendix C-2 ............. Fluroide Appendix C-3 ................ Sulfate

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APPENDIX C-1 Distribution of Nitrate Concentrations by Range in Concentration Categories, Averages and Medians for Paleozoic and Cretaceous Aquifers Cl-1

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n ...... NJ The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Hickory aquifer. Distribution By Ranges in Concentration Categories in County(s) Number of Milligrams Per Liter (mgll) and Other Analyses <0.4 to 1.0 1.1 to 5.0 5.1 to 10.6 10.7 to 44 Blanco and Gillespie 35 19 9 Percent Distribution 100 54.3 25.7 By Categories Range in Analyses <0.4-0.8 1.1-3.5 Arithmetic Averages 0.3 2.2 Analyses Medians 0.40 2.30 Category Medians 0.50 3.05 Notes: 2.9% Exceed Primary Standard MCL of 44.3 mg/1. 14.3% Exceed Regional Average of 10.6 mg/1. 45.7% Exceed Ambient Levd of 1.0 mgll or less. 2 4 5.7 11.4 9.0-9.4 15-43 9.2 28 9.20 29.00 7.85 27.35 Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >44.3 (mgll) (mg/1) (mg/1) 7.6 56 2.9 111 111 7.6 111 7.8 111 7.8

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The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Mid-Cambrian aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Average.s Medians Median and Other Analyses <0.4 to 1.0 1.1to5.0 5.1 to 10.6 10.7 to 44 >44.3 (mgll) (mg/1) (mg/1) Blanco and Gillespie 31 7 5 6 10 3 23.9 133 Percent Distribution 100 22.6 16.1 19.4 32.2 9.7 By Categories Range in Analyses <0.4-1.0 1.1-5.0 6.0-10.0 15-41 58-265 Arithmetic (j Averages 0.2 2.9 7.3 25 144 23.9 -cjQ Analyses Medians 0.50 3.05 8.00 28.00 162 26.9 Category Medians 0.50 3.05 7.85 27.35 162 26.6 Notes: 9.7o/o Exceed Primary Standard MCL of 44.3 mg/1. 41.9o/o Exceed Regional Average of 10.6 mg/1. 77.4o/o Exceed Ambient Level of 1.0 mg/1 or less.

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n ..... The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Ellenburger-San Saba aquifer. County(s) and Other Blanco and Gillespie Percent Distribution By Categories Range in Analyses Arithmetic Averages Analyses Medians Category Medians Number of Analyses 37 100 <0.4 to 1.0 8 21.6 0.1-0.8 0.3 0.45 0.50 Distribution By Ranges in Concentration Categories in Milligrams Per Liter (mgll) 1.1 to 5.0 5.1 to 10.6 10.7 to 44 6 9 12 16.2 24.3 32.5 1.1-4.8 6.0-9.7 10.7-34 2.7 7.7 20 2.95 7.85 22.35 3.05 7.85 27.35 Notes: 5.4% Exceed Primary Standard MCL of 44.3 mg/1. 37.8% Ex<:eed Regional Average of 10.6 mg/1. 78.4% Exceed Ambient Level of 1.0 mgll or less. >44.3 2 5.4 54-46 55 55 55 Arithmetic Averages (mgll) 11.8 11.8 Average and Median Concentrations Analyses Category Medians Median (mgll) (mg/1) 28.1 12.7 14.3

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n c. The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Marble Falls aquifer. County(s) and Other Blanco Percent Distribution By Categories Range in Analyses Arithmetic Averages Analyses Medians Category Medians Number of Analyses 11 100 <0.4 to 1.0 0 0 0 0 0 Distribution By Ranges in Concentration Categories in Milligrams Per Liter (mg/1) 1.1 to 5.0 5.1 to 10.6 10.7 to 44 0 7 9.1 0 63.6 1.8 0 11-38 1.8 0 27 1.8 0 24.50 3.05 0 27.35 Notes: 27.3o/o Exceed Primary Standard MCL of 44.3 mg/1. 90.9o/o Exceed Regional Average of 10.6 mg/1. 1 OOo/o Exceed Ambient Level of 1.0 mg/1 or less. >44.3 3 27.3 70-705 418 388 388 Average and Median Concentrations Arithmetic Averages (mgll) 131 131 Analyses Category Medians Median (mg/1) (mg/1) 353 122 124

PAGE 120

The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Lower Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses <0.4 to 1.0 1.1 to 5.0 5.1 to 10.6 10.7 to 44 >44.3 (mg/1) (mg/1) (mg/1) Bandera 5 5 0 0 0 0 0.5 0.5 Hays 8 4 3 1 0 0 2.7 3.0 Kendall 6 4 1 0 0 5.1 14.0 Kerr 3 3 0 0 0 0 <0.4 <0.4 Iram M .12 .ill J.. ..5. 2. 3ti Totals 88 58 14 8 6 2 4.3 34.6 Percent Distribution 100 65.9 15.9 9.1 6.8 2.3 C") By Categories Range in Analyses <0.4-1.0 1.1-5.0 5.9-10.0 17-44 56-69 Arithmetic Averages 0.1 3.3 6.9 24 63 4.3 Analyses Medians 0.50 3.25 7.95 30.50 62.50 4.9 Category Medians 0.50 3.05 7.85 27.35 62.50 4.6 Notes: 2.3o/o Exceed Primary Standard MCL of 44.3 mgll. 9.1o/o Exceed Regional Average of 10.6 mg/1. 34.1 o/o Exceed Ambient Level of 1.0 mgll or less.

PAGE 121

The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Middle Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses <0.4 to 1.0 1.1 to 5.0 5.1 to 10.6 10.7 to 44 >44.3 (mg/l) (mgll) (mg/1) Bandera 15 13 2 0 0 0 0.6 2.4 Blanco 20 9 2 3 4 2 13.3 32.1 Co mal 8 3 4 1 0 0 2.5 3.1 Hays 36 25 9 2 0 0 1.0 3.6 Gillespie 22 5 4 4 6 3 23.2 78 Kendall 65 36 14 7 7 6.5 74 Kerr 21 20 0 0 1 0 2.0 19.1 :wm 22 ..ll lZ :z ...5. 1 2A ..llJ. Totals 249 143 52 24 23 7 6.3 78 Percent (.""} Distribution 100 57.4 20.9 9.6 9.3 2.8 ...... I By Categories Range in Analyses <0.4-1.0 1.1-5.0 5.1-10.0 14-44 49-155 Arithmetic Averages 0.1 2.7 7.2 27 89 6.3 Analyses Medians 0.50 3.05 7.75 29.00 102 7.2 Category Medians 0.50 3.05 7.85 27.35 102 7.1 Notes: 2.8o/o Exceed Primary Standard MCL of 44.3 mg/1. 12.1% Exceed Regional Average of 10.6 mg/1. 42.6% Exceed Ambient Level of 1.0 mg/l or less.

PAGE 122

The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for rhe Upper Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses <0.4 to 1.0 1.1 to 5.0 5.1 to 10.6 10.7 to 44 >44.3 (mg/1) (mg/1) (mg/1) Bandera 24 15 4 3 2 0 2.7 8.0 Blanco 12 2 6 3 0 7.2 20.6 Hays 26 10 7 6 1 2 7.4 30.0 Kendall 12 6 2 2 2 0 5.7 16.5 Kerr 5 2 3 0 0 0 1.1 1.2 Medina 8 0 5 3 0 0 4.3 5.0 IwU M ..28. 12. .1 1. 1 !iJ. Totals 135 63 39 20 10 3 5.1 44.1 Percent Distribution 100 46.7 28.9 14.8 7.4 2.2 (') ...... By Categories & Range in Analyses <0.4-1.0 1.1-5.0 5.1-10.2 11-43 55-88 Arithmetic Averages 0.1 2.6 7.1 24 68 5.1 Analyses Medians 0.50 3.05 7.65 27.00 72 5.8 Category Medians 0.50 3.05 7.85 27.35 72 5.9 Notes: 2.2% Exceed Primary Standard MCL of 44.3 mg/1. 9.6o/o Exceed Regional Average of 10.6 mg/1. 53.3% Exceed Ambient Level of 1.0 mg/1 or less.

PAGE 123

The following table provides the distribution of nitrate concentrations by range in concentration Categories, averages, and medians, for the Edwards Plateau aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mgll) Averages Medians Median and Other Analyses <0.4 to 1.0 1.1 to 5.0 5.1 to 10.6 10.7 to 44 >44.3 (mg/1) (mgll) (mg/1) Bandera 17 1 5 5 4 2 16.9 5.3 Gillespie 85 26 22 10 19 8 19.9 19.2 Km: ..1 1 2 .Q .Q .Q u .2...a Totals 105 28 29 15 23 10 19.0 192 Percent Distribution 100 26.7 27.6 14.3 21.9 9.5 By Categories Range in C') Analyses <0.4-0.8 1.5-5.0 5.4-10.0 11-38 48-384 -tb Arithmetic Averages 0.2 3.2 6.8 22 129 19.0 Analyses Medians 0.40 3.25 7.70 24.50 216 28.0 Category Medians 0.5 3.05 7.85 27.35 216 28.7 Notes: 9.5% Exceed Primary Standard MCL of 44.3 mg/1. 31.4o/o Exceed Regional Average of 10.6 mg/1. 73.3o/o Exceed Ambient Level of 1.0 mg/1 or less.

PAGE 124

APPENDIX C-2 Distribution of Fluoride Concentrations by Range in Concentration Categories, Averages Medians for the Paleozoic and Cretaceous Aquifers C2-l

PAGE 125

n .t\0 The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Hickory aquifer. Distribution By Ranges in Concentration Categories in County(s) Number of Milligrams Per Liter (mgll) and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 Blanco and Gillespie 37 18 13 Percent Distribution 100 48.7 35.1 By Categories Range in Analyses 0.2-0.5 0.6-1.0 Arithmetic Averages 0.4 0.8 Analyses Medians 0.35 0.80 Category Medians 0.25 0.90 Notes: 2.7% Exceed Secondary Standard MCL of2.0 mg/1. None Exceed Primary Standard MCL of 4.0 mg/1. 16.2% Exceed Regional Average of 1.2 mg/1. 5 13.5 2.7 1.7-1.9 2.4 1.8 2.4 1.80 2.4 1.65 3.05 Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >4.0 (mgll) (mg/1) (mg/1) 0 0.8 1.3 0 0 0 0.8 0 0.8 0 0.7

PAGE 126

C1 N) I (J:) The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Mid-Cambrian aquifer. Distribution By Ranges in Concentration Categories in County(s) Number of Milligrams Per Liter (mg/1) and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 Blanco and Gillespie 10 3 4 Percent Distribution 100 30.0 40.0 By Category Range in Analyses 0.4-0.5 0.7-1.1 Arithmetic Averages 0.5 1.0 Analyses Medians 0.45 0.90 Category Medians 0.25 0.90 Notes: 30.0% Exceed Regional Average of 1.2 mg/l. 20.0% Exceed Secondary Standard MCL of2.0 mg/l. None Exceed Primary Standard MCL of 4.0 mg/l. 2 10.0 20.0 1.3 3.1-4.0 1.3 3.6 1.30 3.55 1.65 3.05 Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >4.0 (mg/1) (mg/1) (mgli) 0 1.4 2.2 0 0 0 1.4 0 1.3 0 1.2

PAGE 127

C') N) The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Ellenburger-San Saba aquifer. Distribution By Ranges in Concentration Categories in County(s) Number of Milligrams Per Liter (mg/!) and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 Blanco and Gillespie 38 21 16 0 Percent Distribution 100 55.3 42.1 2.6 0 By Category Range in Analyses 0.1-0.5 0.6-1.2 1.7 0 Arithmjetic Averages 0.3 0.7 1.7 0 Analyses Medians 0.30 0.90 1.7 0 Category Medians 0.25 0.90 1.65 0 Notes: None Exceed Secondary Standard MCL of 2.0 mg/1 and Primary Standard MCL of 4.0 mg/1. 2.6o/o Exceed Regional Average of 1.2 mg/1. Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >4.0 (mg/1) (mg/1) (mgll) 0 0.5 0.9 0 0 0 0.5 0 0.6 0 0.6

PAGE 128

The following table provides the distribution of fluoride con.:enrrarions by range in Cuegories, averages, and medians, for the Marble Falls aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category C:ounty(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 >4.0 (mg/1) (mg/1) (mgll) Blanco 4 4 0 0 0 () 0.2 0.3 Percent Distribution 100 100 Ry Category Range in An;.1!yses {\ 1 () /, v .• -v."1 0 0 0 (• Arithmetic Averages 0.2 0 0 0 0 0.2 n Analyses <), Medians 0.25 0 0 0 0 0.3 Category Medians 0.25 0 0 0 0 0.3 Notes: None Exceed Secondary Standard MCL of 2.0 mg/1, Primary Standard MCL of 4.0 mg/1. and Regional Average of 1.2 mg/1.

PAGE 129

(') N:) The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Lower Triniry aquifer. Distribution By Ranges in Concentration Categories in County(s) Number of Milligrams Per Liter (mg/1) and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 Bandera 5 0 0 Hays 8 4 2 Kendall 6 0 2 Kerr 8 0 4 Travis .@ 15. 13. I Totals 95 19 21 Percent Distribution 100 20.0 22.1 By Categories Range in Analyses 0.0-0.4 0.6-1.2 Arithmetic Averages 0.2 0.9 Analyses Medians 0.20 0.90 Category Medians 0.25 0.90 Notes: 33.7% Exceed Secondary Standard MCL of2.0 mg/1. 8.4% Exceed Primary Standard MCL of 4.0 mg/1. 57.9% Exceed Regional Average of 1.2 mg/1. 2 3 1 4 0 4 0 ll 2Q 23 24 24.2 25.3 1.3-2.0 2.1-3.9 1.6 3.0 1.65 3.00 1.65 3.05 Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >4.0 (mg/1) (mgll) (mg/1) 0 2.4 2.4 0 0.7 1.3 0 1.5 1.6 0 1.3 1.3 .8. L2 2:1. 8 1.8 2.7 8.4 4.2-5.3 4.6 1.8 4.75 1.8 4.75 1.8

PAGE 130

The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Middle Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category C..ounty(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 >4.0 (mg/1) (mgll) (mg/1) Bandera 13 0 0 0 10 3 3.2 3.6 Blanco 22 12 3 3 3 1.0 2.1 Co mal 8 6 2 0 0 0 0.4 0.7 Hays 36 10 7 4 15 0 1.0 3.6 Gillespie 22 18 3 1 0 0 0.5 0.7 Kendall 65 27 12 14 9 3 1.3 2.6 Kerr 28 0 4 23 1 0 1.5 1.5 Iram .1Q .22 J.2 lQ ll u 3..6 Total 264 102 43 52 48 19 1.5 3.5 Percent (') Distribution 100 38.6 16.3 19.7 18.2 7.2 By Categories Range in Analyses 0.0-0.5 0.6-1.2 1.3-2.0 2.1-3.9 4.1-7.0 Arithmetic Averages 0.3 0.9 1.7 2.8 5.0 1.5 Analyses Medians 0.25 0.90 1.65 3.00 5.55 1.5 Category Medians 0.25 0.90 1.65 3.05 5.55 1.5 Notes: 25.4% Exceed Secondary Standard MCL of 2.0 mg/l. 7.2% Exceed Primary Standard MCL of 4.0 mg/1. 45.1% Exceed REgional Average of 1.2 mg/l.

PAGE 131

The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Upper Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in . Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mgll) Averages Ivie4.0 (mg/1) (mg/1) (mg/1) Bandera 16 4 3 4 3 2 1.7 2.4 Blanco 16 7 5 1 3 0 1.0 1.6 Hays 25 12 2 5 5 1 1.3 2.2 Kendall 12 4 3 1 4 0 1.3 1.7 Kerr 4 1 1 0 2 0 1.8 2.0 Medina 7 7 0 0 0 0 0.1 0.1 lZ ll 1 12 ..i L2 ll Totals 128 52 27 13 29 7 1.4 2.8 Percent Distribution 100 40.6 21.1 10.2 22.6 5.5 (1 By Categories I 00 Range in Analyses 0.0-0.5 0.6-1.2 1.3-2.0 2.1-4.0 4.3-5.5 Arithmetic Averages 0.3 0.9 1.6 2.9 4.7 1.4 Analyses Medians 0.25 0.90 1.65 3.05 4.90 1.4 Category Medians 0.25 0.90 1.65 3.05 4.90 1.4 Notes: 28.i% Exceed Secondary Standard MCL of2.0 mg/l. 5.5% Exceed Primary Standard MCL of 4.0 mg/1. 38.3% Exceed Regional Average of 1.2 mg/l.

PAGE 132

The following table provides the distribution of fluoride concentrations by range in concentration Categories, averages, and medians, for the Edwards Plateau aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mgii) .. :; and Other Analyses 0.0 to 0.5 0.6 to 1.2 1.3 to 2.0 2.1 to 4.0 >4.0 (mg/1) (mg/1) (mgll) Bandera 12 12 0 0 0 0 0.1 0.1 Gillespie 85 81 4 0 0 0 0.3 0.5 Km ..1 _.1 Q Q Q Q M M Totals 100 96 4 0 0 0 0.3 0.4 Percent Distribution 100 96.0 4.0 0 0 0 By Categories Range in n Analyses 0.0-0.5 0.6-0.8 0 0 0 N) ch Arithmetic Averages 0.3 0.7 0 0 0 0.3 Analyses Medians 0.25 0.70 0 0 0 0.3 Category Medians 0.25 0.90 0 0 0 0.3 Notes: None Exceed Secondary Standard MCL of 2.0 mg/1, Primary Standard MCL of 4.0 mg/1 and Regional Average of 1.2 mg/1.

PAGE 133

APPENDIX C3 Distribution of Sulfate Concentrations by Range in Concentration Categories, Averages and Medians for the Paleozoidc and Cretaceous Aquifers C3-l

PAGE 134

n Cf NJ The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Hickory aquifer. Distribution By Ranges in Concentration Categories in r.nnntvl..:) Nu..'!lber .Milligi.ui:aoi (mgil) -----,-, and Other Analyses <4 to 99 100 to 203 204 to 250 251-300 Blanco and Gillespie 48 42 5 0 Percent Distribution 100 87.5 10.4 0 2.1 By Categories Range in Analyses 7-92 100-190 0 267 Arithmetic Averages 41 130 0 267 Analyses Medians 49.5 145.0 0 267 Category Medians 51.0 151.5 0 267 Notes: None Exceed Secondary Standard MCL of 300 mg/1. 2.1 o/o Exceed Regional Average of 203 mg/1. Average and Median Concentrations Arithmetic Analyses Category Averages Medians Median >300 (mg/1) (mg/1) (mg/1) 0 55 137 0 0 0 55 0 64 66

PAGE 135

Notes: None Exceed Secondary Standard MCL of 300 mg/l. None Exceed Regional Average of 203 mg/l.

PAGE 136

The following table provides the distriburion of sulfate concentrations by range in concentration Categories, averages, and medians, for the Ellenburger-San Saba aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/l) Averages Medians Median and Other Analyses <4 to 99 100 to 203 204 to 250 251-300 >300 (mg/1) (mgll) (mg/1) Blanco and Gillespie 50 50 0 0 0 0 35 50 Percent Distribution 100 100 0 0 0 0 By Category Range in Analyses 8-91 0 0 0 0 Arithmetic n Averages 35 0 0 0 0 35 (.)0 Analyses Medians 49.5 0 0 0 0 50 Category Medians 51.0 0 0 0 0 51 Notes: None Exceed Secondary Standard MCL of 300 mg/l and Regional Average of 203 mg/l.

PAGE 137

The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Marble Falls aquifer. <4 to 99 14 93.3 11-45 22 28.0 51.0 Distribution By Ranges in Concentration Categories in Milligrams Per Liter (mg/1) 100 to 203 204 to 250 251-300 0 0 6.7 0 0 136 0 0 136 136 136 Notes: None Exceed Secondary Standard MCL of300 mg/l and Regional Average of203 mg/l. >300 0 0 0 Arithmetic Averages (melD 30 30 Average and Median Concentrations Analyses Category Medians Median {melD (ml!:/1) 74 35 57

PAGE 138

The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Lower Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category r,.. ..... .,.t .. \ "l .r ... n T •. I II\ Averages .Medians Median _"_ ..... , , .... , J.Y.l.llllf:,lcUII;) I.C:I LllCl \lllg/1} and Other Analyses <4 to 99 100 to 203 204 to 250 251-300 >300 (mg/1) (mgll) (mg/1) Bandera 5 4 0 0 0 69 84 Hays 8 5 0 0 0 3 286 535 Kendall 6 0 3 1 1 229 248 Kerr 8 6 2 0 0 0 68 73 Travis {il .2.2 z .2 .2. 22 1Q1 .2.Q.2 Totals 94 38 13 4 10 29 265 903 Percent Distribution 100 40.4 13.8 4.3 10.6 30.9 By Category n Range in t.>O a, Analyses 15-99 105-200 217-224 257-287 306-1790 Arithmetic Averages 41 145 221 272 617 265 Analyses Medians 57.0 152.5 220.5 272.0 1,048 405 Category Medians 51.0 151.5 227.5 275.5 1,048 404 Notes: 30.9% Exceed Secondary Standard MCL of 300 mg/1. 45.8% Exceed Regional Average of203 mg/1.

PAGE 139

The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Middle Trinity aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median a.."ld Other AnalysG nn iGG lo 203 204 (0 150 151-300 >jUU {mgll) (mgll) (mg/1) '"'t II.U 77 Bandera 13 0 6 0 I 6 386 860 Blanco 36 26 3 1 0 6 268 I,456 Co mal 8 8 0 0 0 0 27 48 Hays 36 14 4 2 4 I2 350 704 Gillespie 22 2I 1 0 0 0 33 55 Kendall 65 36 I6 4 8 I 52 852 Kerr 30 I7 I2 0 0 I 90 28I Travis Zl .li a 2 1 22 ill L2B.2 Totals 281 157 50 12 7 55 252 1,681 Percent C') Distribution IOO 55.8 I7.8 4.3 2.5 I9.6 (JQ I -..J By Category Range in Analyses 2-96 IOI-I97 205-245 253-299 3I0-3,360 Arithmetic Averages 33 I48 22I 273 976 252 Analyses Medians 49.0 I49.0 225.0 276.0 I,835 430 Category Medians 51.0 I51.5 227.0 275.5 I,835 43I Notes: I9.6o/o Exceed Secondary Standard MCL of300 mg/1. I6.4o/o Exceed Regional Average of203 mg/1.

PAGE 140

The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Upper Trinity aquifer. Average and Median Distribution Ry Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses <4 to')') lUU to lOj l.o4 to 250 25i-30u >300 I II\ \lllgt ., {mg/!) (mg!l} Blanco and Bandera 26 7 2 15 802 1,110 Blanco 23 16 1 0 0 6 353 930 Hays 26 15 3 1 2 5 365 968 Kendall 12 4 2 2 0 4 260 350 Kerr 6 2 0 0 0 4 867 1,023 Medina 8 7 0 0 0 1 69 218 :w.m ll .1.2. f Q _1. ill LlBZ Totals 149 72 27 8 3 39 360 1,187 Percent n Distribution 100 48.3 18.1 5.4 2.0 26.2 & By Category Range in Analyses 4-99 100-202 206-244 251-279 327-2370 Arithmetic Averages 29 134 227 263 1,162 360 Analyses Medians 51.5 151.0 225.0 265.0 1.349 423 Category Medians 51.0 151.5 227.0 275.5 1,349 423 Notes: 26.2% Exceed Secondary Standard of 300 mg/l. 33.6% Exceed Regional Average of 203 mg/l.

PAGE 141

The following table provides the distribution of sulfate concentrations by range in concentration Categories, averages, and medians, for the Edwards Plateau aquifer. Average and Median Distribution By Concentrations Ranges in Concentration Categories in Arithmetic Analyses Category County(s) Number of Milligrams Per Liter (mg/1) Averages Medians Median and Other Analyses <4 to 99 100 to 203 204 to 250 251-300 >300 (mgll) (mg/1) (mg!l) Bandera 17 17 0 0 0 0 7 12 Gillespie 85 84 1 0 0 0 16 66 Km: ..1 ..1 .Q .Q .Q .Q ll 12 Totals 106 105 1 0 0 0 14 66 Percent Distribution 100 99.0 1.0 0 0 0 By Category Range in n Analyses <4-70 130 0 0 0 (,)0 cb Arithmetic Average 13 130 0 0 0 14 Analyses Medians 36.0 130 0 0 0 37 Category Medians 51.0 130 0 0 0 52 Notes: None Exceed Secondary Standard MCL of 300 mg/1 and Regional Average of 203 mg/1.

PAGE 142

APPENDIX D Estimated 1985 Ground-Water Pumpage by County, by Use Catagory, by Aquifer, in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in the Hill Country Study Area, Texas

PAGE 143

Estimated 1985 Ground-Water Purnpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Bandera County Edwards Trinity EllenburgerNo. Plate:;m C'!ronn . Marble Falls San Saba Mid-Cambrian Hickory Precambrian Total Wells Use Category Aquifer Aquifers Aquifer Aquifer Aq.llfer Aquifer Aquifer Pwnpage Percent Used Major Public Supply •Bandera 199 199 13.3 3 Other Public Supply 165 165 11.0 14 Rural Domestic Supply 47 743 790 52.8 Unknown Manufacturing Power 9 Mining 24 24 1.6 Unknown Irrigation 89 89 6.0 12 Livestock 23 206 229 15.3 Unknown Total Pumpage and Wells Used 70 1,426 1,496 100.0 29 Percent 4.7 95.3 100.0

PAGE 144

Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Blanco County Edwards Trinity Ellenburger-No. Plateau Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Total Wells Use Category Aquifer Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer Pump age Percent Used Major Public Supply •Johnson City1 152 152 13.9 2 Other Public Supply 15 15 1.4 2 Rural Domestic Supply 253 5 42 17 11 4 332 30.3 Unknown Manufacturing Power 0 Mining Irrigation 64 150 40 254 23.2 142 Livestock 236 6 54 21 19 5 341 31.2 Unknown Total Pwnpage and Wells Used 568 11 398 38 70 9 1,094 100.0 18 Percent 51.9 1.0 36.4 3.5 6.4 0.8 100.0 1 Also used 58 acre-feet of surface water from the Pedernales River. 2 Includes approximately 6 Trinity Group, 6 Ellenburger-San Saba and 2 Hickory wells.

PAGE 145

Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Comal County Edwards Trinity Ellenburger-No. Plateau Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Total WeDs Use Category Aquifer Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer Pwnpage Percent Used Major Public Supply •Canyon Lake Forest Utility 178 178 13.0 4 •General Utilities & Development Co. 161 161 11.8 6 •Haskin Water Supply 93 93 6.8 99 •W&W Water Co. 292 292 21.4 14 9 Other Public Supply 454 454 33.2 57 (.)0 Rural Domestic Supply 55 55 4.0 Unknown Manufacturing Power Mining Irrigation Livestock 134 134 9.8 Unknown Total Pumpage and Wells Used 1,367 1,367 100.0 90 Percent 100.0 100.0

PAGE 146

0 Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Gillespie County Trinity EllenburgerEdwards Plateau Aquifer Group Marble Falls San Saba Mid-Cambrian Use Category Aquifer Aquifer Major Public Supply • Fredericksburg l 1,828 Other Public Supply 7 7 39 Rural Domestic Supply 287 336 7 99 8 Manufacturing Power Mining 16 Irrigation 103 890 376 Livestock 160 182 5 55 5 Total Pumpage and Wells Used 557 1,415 12 2,413 13 Percent 10.8 27.6 0.2 47.1 0.3 1 Very small amount which is included in Hickory aquifer pumpage (203 acre-feet). 2 Includes 5 Ellenburger-San Saba wells, 2 Hickory wells and 1 Trinity Group-Hickory well. 3 Includes 1 Edwards Plateau, 1 Trinity Group, 5 Ellenburger-San Saba, 7 Hickory and l Precambrian wells. 4 Includes 3 Edwards Plateau, 24 Ttinity Group, 10 Ellenbmger-San Saba and 9 Hickory Wells. Hickory Aquifer 203 29 82 342 45 701 13.7 Precambrian Aquifer 3 6 4 13 0.3 Total Pwnpage 2,031 85 825 16 1,711 456 5,124 100.0 Percent 39.6 1.7 16.1 0.3 33.4 8.9 100.0 No. Wells Used 82 153 Unknown Unknown 464 Unknown 69

PAGE 147

Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Hays County Edwards Trinity Ellenburger-No. Plateau Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Total Wells Use Category Aquifer Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer Pwnpage Percent Used Major Public Supply •Dripping Springs wsc 294 294 16.5 2 •Wimberly WSC 363 363 20.4 5 •Woodcreek Utilities 493 493 27.7 3 Other Public Supply 24 24 1.4 5 0 Rural Domestic Supply 300 300 16.9 Unknown Manufacturing Power Mining Irrigation Livestock 303 303 17.1 Unknown Total Pumpage and Wells Used 1,777 1,777 100.0 15 Percent 100.0 100.0

PAGE 148

0 6 Edwards Plateau Use Category Aquifer Major Public Supply •Boeme1 •Comfort Other Public Supply Rural Domestic Supply Manufacturing Power Mining Irrigation Livestock Total Pumpage and Wells Used Percent Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Kendall County Trinity Ellenburger-Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer 336 217 129 856 5 132 326 2,001 100.0 1 Also used 451 acre-feet of surface water from a city lake on Cibolo Creek. No. Total Wells Pumpage Percent Used 336 16.8 8 217 10.8 5 129 6.5 13 856 42.8 Unknown 5 0.2 132 6.6 12 326 16.3 Unknown 2,001 100.0 39 100.0

PAGE 149

Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Kerr County Edwards Trinity Ellenburger-No. Plateau Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Total Wells Use Category Aquifer Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer Pwnpage Percent Used Major Public Supply •Kenville1 872 872 25.3 13 •Ingram 376 376 10.9 4 •Kenville South Water Co. 235 235 6.8 4 •Hill Country Utilities 197 197 5.7 21 Other Public Supply 431 431 12.5 36 0 Rural Domestic Supply 252 470 722 21.0 Unknown Manufacturing Power Mining 81 81 2.4 Unknown Irrigation 204 204 5.9 14 Livestock 213 114 327 9.5 Unknown Total Pumpage and Wells Used 465 2,980 3,445 100.0 92 Percent 13.5 86.5 100 1 Also used 2,870 acre-feet of surface water from Quinlan Creek and the Guadalupe River.

PAGE 150

0 00 Use Category Major Public Supply Other Public Supply Ruraj Domestic Supply Manufacturing Power Mining Irrigation Livestock Total Pumpage and Wells Used Percent Edwards Plateau Aquifer Estimated 1985 Ground-Water Pumpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Medina County Trinity Group Marble Falls Aquifers ilquifer 5 78 17 100 100.0 EllenburgerSan Saba Mid-Cambrian ilquifer ilquifer Hickory ilquifer Precambrian ilquifer Total Pumpage 5 78 17 100 100.0 Percent 5.0 78.0 17.0 100.0 No. WeDs Used 4 Unknown Unknown Unknown 4

PAGE 151

0 cb Edwards Plateau Use Category Aquifer Major Public Supply •Apache Shores, Inc. Other Public Supply Rural Domestic Supply Manufacturing Power Mining Irrigation Livestock Total Pwnpage and Wells Used Percent E.4itimated 1985 Ground-Water Purnpage by Use Category by Aquifer in Acre-Feet and Estimated Number of Large-Capacity Wells Used in 1985 in Travis County Trinity Ellenburger-Group Marble Falls San Saba Mid-Cambrian Hickory Precambrian Aquifers Aquifer Aquifer Aquifer Aquifer Aquifer 125 !58 6 1,938 108 2,329 6 99.7 0.3 1 Includes 15 Trinity Group and 2 Marble Falls wells. No. Total Wells Pwnpage Percent Used 125 5.4 4 164 7.0 }7 I 1,938 83.0 Unknown 108 4.6 Unknown 2,335 100.0 21 100.0

PAGE 152

APPENDIX E Estimated Water Use in 1980 and 1985 by County (Texas Water Development Board, 1988) Ev-.tluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country ofC'A:ntral Texas July 1992

PAGE 153

Evaluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country ofCentr.al Texas July 1992 Estimated Water Use in 1980 and 1985 in Bandera County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Water Use Ground Surface Total Ground Surface Total Category Water Water Use Water Water Use Public Supply and Rural Domestic 910 -0-910 1,154 18 1,172 Manufacturing 8 -08 -0-0-0-Power -0-0-0-0-0--0Mining -0--0--024 -024 Irrigation 99 439 538 89 160 249 Livestock 303 73 376 229 55 284 County Total 1,320 512 1,832 1,496 233 1,729 Water Use Estimated Water Use in 1980 and 1985 in Blanco County, Texas Estimated Estimated 1980 'Vater Use in Acre-Feet 1985 Water Use in Acre-Feet Water Use Ground Surface Total Ground Surface Total Category Water Water Use Water Water Use Public Supply and Rural Domestic 350 386 736 499 310 809 Manufacturing -01 -01 1 Power -0--0-0-0-0-0Mining -0-0--0--0-0--0Irrigation 149 76 225 254 45 299 Livestock 387 87 474 341 85 426 County Total 886 550 1,436 1,094 441 1,535 Water Use E-1

PAGE 154

Water Use Category Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Use Water Use Category Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Use fo:\'aluation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Estimated Water Use in 1980 and 1985 in Comal County, Texas Estimated 1980 \\rater Use in Acre-Feet 1985 Water Use in Acre-Feet Ground Surface Total Ground Surface Total Water Water Use Water Water Use 920 -0-920 1,233 -01,233 -0-0-0-0-0-0--0--0-0-0--0-0--0-0--0--0--0-0-30 56 86 -0--0--0167 41 208 134 33 167 1,117 97 1,214 1,367 33 1,400 Estimated Water Use in 1980 and 1985 in Gillespie County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Ground Surface Total Ground Surface Total Water Water Use Water Water Use 2,273 -02,273 2,785 --02,785 505 80 585 156 117 273 -0--0-0--0--0--0--0--0--016 --016 800 880 1,680 1,711 48 1,859 664 497 1,161 456 456 912 4,242 1,457 5,699 5,124 721 5,845 E-2

PAGE 155

Ev-aluation of the Ground-Water Resources of the Paleozoic a:1d Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Water Use Category Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock Cowtty Total Water Use Water Use Category Public Supply and Rura] Domestic Man ufactming Power Mining Irrigation Livestock Cowtty Total Water Use Estimated Water Use in 1980 and 1985 Hays County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Growtd Surface Total Growtd Surface Total Water Water Use Water Water Use 723 -0723 1,474 -01,474 -0--0--0--0-0--0--0--0-0--0--0--0--0--0--0-0--0--0--042 42 -054 54 57 339 303 62 365 1,005 99 1,104 1,777 116 1,893 Estimated Water Use in 1980 and 1985 in Kendall County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Ground Surface Total Ground Surface Total Water Water Use Water Water Use 1,103 381 1,484 1,538 451 1,989 4 3 7 5 -05 -0-0--0--0-0--0--0--0-0-0--0-0-200 336 536 132 18 150 441 98 539 326 80 406 1,748 818 2,566 2,001 549 2,550 E-3

PAGE 156

Water Use Category Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Use Water Use Category Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Use Ev-,duation of the Ground-Water Re!IOurces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Estimated Water Use in 1980 and 1985 in Kerr County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Ground Surface Total Ground Surface Total Water Water Use Water Water Use 4,764 96 4,860 2,831 2,864 5,695 19 -019 2 5 7 -0-0--0-0--0-0--0-0-081 -081 500 784 1,284 204 996 1,200 433 102 535 327 80 407 5,716 982 6,698 3,445 3,945 7,390 Estimated Water Use in 1980 and 1985 in Medina County, Texas Estimated Estimated 1980 Water Use in Acre-Feet 1985 Water Use in Acre-Feet Ground Surface Total Ground Surface Total Water Water Use Water Water Use 77 -077 83 -083 -0-0-0--0--0--0--0--0--0--0--0-0-0-0-0-0-0--0--0--0--0-0-0--0-30 150 180 17 154 171 107 150 257 100 154 254 E-4

PAGE 157

E\'aluation of lh< Ground-W
PAGE 158

APPENDIX F Projected Water Demands for 1990,2000, and 2010 by County (Texas Water Development Board, 1988) E,,lluation of the Ground-Water Re!IOurcc• of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992

PAGE 159

ho•luation of the Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Countrv of(:C,ntrdl Texas .July 1992 ' Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Demands Water DemandCatagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Demands Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Demands Projected Water Demands For 1990, 2000, and 2010 in Bandera County, Texas Projected Water Demands in Acre-Feet 1990 2000 2010 2,666 3,429 12 15 -0--0--0-0213 217 440 506 3,331 4,167 Projected Water Demands For 1990, 2000, and 2010 in Blanco County, Texas 3,966 17 -0-0219 506 4,708 Projected Water Demands in Acre-Feet 1990 2000 2010 1,340 1,803 2 2 -0--06 12 218 222 556 639 2,122 2,678 Projected Water Demands For 1990, 2000, and 2010 in Comal County, Texas 2,267 3 -09 224 639 3,142 Projected Water Demands in Acre-Feet 1990 2000 2010 1,310 1,847 2,272 -0-0-0-0-0-0-0-0-0116 117 119 245 283 283 1,671 2,247 2,674 F-1

PAGE 160

Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation livestock Projected Water Demands For 1990, 2000, and 2010 in GiUespie County, Texas b•.tluation of the Ground-Water Re50urces of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas July 1992 Projected Water Demands in Acre-Feet 1990 2000 2010 3,719 4,523 5,029 776 1,044 1,330 -0--0-06 12 9 1,374 1,395 1,413 1,347 1,535 1,535 County Total Water Demands 7,222 8,509 9,316 Projected Water Demands For 1990, 2000, and 2010 in Hays County, Texas Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Demands Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation Livestock County Total Water Demands Projected Water Demands in Acre-Feet 1990 2000 2010 1,273 2,035 -0--0--0--0--0--075 77 399 459 1,747 2,571 Projected Water Demands For 1990, 2000, and 2010 in Kendall County, Texas 2,828 -0-0--077 459 3,364 Projected Water Demands in Acre-Feet 1990 2000 2010 3,158 3,974 4,571 11 13 17 -0--0-06 12 9 601 610 618 630 722 722 4,406 5,331 5,937 F-2

PAGE 161

E\'alualion of lhe Ground-Wal.Cr Reoources of lhc Paleozoic and Cre1.01ceous Aquifers in 1he Hill Counlry Texas July 1992 Projected Water Demands For 1990, 2000, and 2010 in Kerr County, Texas Projected Water Demands in Acre-Feet Water Demand Catagory 1990 2000 Public Supply and Rural Domestic 8,425 10,793 Man ufactming Power Mining Irrigation livestock County Total Water Demands 27 38 -0-06 12 816 828 621 709 9,895 12,380 Projected Demands For 1990, 2000, and 2010 in Medina County, Texas 2010 12,467 49 -09 839 709 14,073 Projected Water Demands in Acre-Feet Water Demand Catagory Public Supply andRural Domestic Manufacturing Power Mining Irrigation livestock County Total Water Demands 1990 123 -0--0--0--0214 337 2000 138 -0--0--0-0248 386 Projected water Demands For 1990, 2000, and 2010 in Travis County, Texas 2010 156 -0--0-0--0248 404 Projected Water Demands in Acre-Feet Water Demand Catagory Public Supply and Rural Domestic Manufacturing Power Mining Irrigation livestock County Total Water Demands 1990 8,355 -0--0-0-0248 8,603 F-3 2000 2010 11,442 13,824 -0-0--0--0-0-0--0-0248 248 11,690 14,072


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