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Groundwater levels in the Balcones Fault zone, Hays and Travis Counties, Texas, 1937-2005

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Title:
Groundwater levels in the Balcones Fault zone, Hays and Travis Counties, Texas, 1937-2005
Alternate Title:
BSEACD Report of Investigations 2006-1025
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Barton Springs/Edwards Aquifer Conservation District
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Technical Report
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ABSTRACT More than 50,000 water-level measurements from 1937 to 2005 in the Balcones Fault Zone of Central Texas were compiled from 49 wells, and one quarry. Data represent water levels from the Edwards, Trinity, and Austin Chalk Aquifers. A simple database was constructed to compile the water-level and well-construction data. The purpose of this report is to provide a foundation for future hydrogeologic investigations. INTRODUCTION Groundwater is an important resource for Texans and constituted nearly 60% of all water used by Texans in 1999 (TWDB, 2002). Aquifers along the Balcones Fault Zone in Central Texas provide an important groundwater resource for industrial, domestic, recreational, and ecological needs. The study area is located along the Balcones Fault Zone of Central Texas within portions of Travis and Hays counties (Figure 1). Water- level data within this report are primarily from wells completed within the Edwards, and to a lesser extent, the Trinity Aquifer. A relatively minor, locally water-bearing unit in the study area is the Austin Chalk. This paper and accompanying database present a compilation of continuous water-level data from groundwater resources in the study area. Groundwater levels provide critical information about the hydrologic relationships of recharge and discharge to storage within an aquifer, and the direction of groundwater flow. Long-term, systematic measurements of water-level data are essential to develop groundwater models and to design, implement, and monitor the effectiveness of groundwater management programs (Taylor and Alley, 2001). This report includes data that numerous agencies have collected over the years: the United States Geological Survey (USGS), Texas Water Development Board (TWDB), Edwards Aquifer Authority (EAA), Hays-Trinity Groundwater Conservation District (HTGCD), San Antonio Water Systems (SAWS), and the Barton Springs/Edwards Aquifer Conservation District (BSEACD). Purpose and Scope This report compiles more than 50,000 water-level measurements made from 1937 to 2005 for 49 wells (and one quarry) completed in the Edwards, Trinity, and Austin Chalk Aquifers. A simple Microsoft(r) Excel-based database was constructed and accompanies this report. The database contains well-completion information and water-level data. The purpose of this report is to provide a foundation for future hydrogeologic investigations and evaluations of water resources in central Texas. The database presented in the report is currently the most comprehensive available for the study area.
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Description
ABSTRACT More than 50,000 water-level measurements from
1937 to 2005 in the Balcones Fault Zone of Central Texas were
compiled from 49 wells, and one quarry. Data represent water
levels from the Edwards, Trinity, and Austin Chalk Aquifers.
A simple database was constructed to compile the water-level
and well-construction data. The purpose of this report is to
provide a foundation for future hydrogeologic investigations.
INTRODUCTION Groundwater is an important resource for Texans
and constituted nearly 60% of all water used by Texans in
1999 (TWDB, 2002). Aquifers along the Balcones Fault Zone in
Central Texas provide an important groundwater resource for
industrial, domestic, recreational, and ecological needs. The
study area is located along the Balcones Fault Zone of
Central Texas within portions of Travis and Hays counties
(Figure 1). Water- level data within this report are
primarily from wells completed within the Edwards, and to a
lesser extent, the Trinity Aquifer. A relatively minor,
locally water-bearing unit in the study area is the Austin
Chalk. This paper and accompanying database present a
compilation of continuous water-level data from groundwater
resources in the study area. Groundwater levels provide
critical information about the hydrologic relationships of
recharge and discharge to storage within an aquifer, and the
direction of groundwater flow. Long-term, systematic
measurements of water-level data are essential to develop
groundwater models and to design, implement, and monitor the
effectiveness of groundwater management programs (Taylor and
Alley, 2001). This report includes data that numerous
agencies have collected over the years: the United States
Geological Survey (USGS), Texas Water Development Board
(TWDB), Edwards Aquifer Authority (EAA), Hays-Trinity
Groundwater Conservation District (HTGCD), San Antonio Water
Systems (SAWS), and the Barton Springs/Edwards Aquifer
Conservation District (BSEACD). Purpose and Scope This report
compiles more than 50,000 water-level measurements made from
1937 to 2005 for 49 wells (and one quarry) completed in the
Edwards, Trinity, and Austin Chalk Aquifers. A simple
Microsoft Excel-based database was constructed and
accompanies this report. The database contains
well-completion information and water-level data. The purpose
of this report is to provide a foundation for future
hydrogeologic investigations and evaluations of water
resources in central Texas. The database presented in the
report is currently the most comprehensive available for the
study area.



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GROUNDWATER LEVELS IN THE BALCONES FAULT ZONE, HAYS AND TRAVIS COUNTIES, TEXAS, 1937-2005 BSEACD Data Series Report 2006-1025 Barton Springs/Edwards Aquifer Conservation District 1124 Regal Row Austin, Texas BSEACD Data Series Report 2006-1025 i

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Disclaimer All of the information provided in this report is believed to be accurate and reliable; however, the Barton Springs/Edwards Aquifer Conservation District (District) assumes no responsibility for any errors or for the use of the information provided. While this report has attempted to provide a comprehensive database of water level data, there may be unintended omissions of data or wells. Cover. Hydrograph of two wells; top hydrograph is from the Zumwald Well (58-50-417) and is highly influenced by conduit development within the aquifer; the lower hydrograph is from the Lovelady Well (58-50-301) and is highly influenced by diffuse flow within the aquifer. BSEACD Data Series Report 2006-1025 ii

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GROUNDWATER LEVELS IN THE BALCONES FAULT ZONE, HAYS AND TRAVIS COUNTIES, TEXAS, 1937-2005 Brian B. Hunt, P.G. and Brian A. Smith, Ph.D., P.G. Kirk Holland, P.G., General Manager Board of Directors Dr. Robert D. LarsenPresident Precinct 3 Jack GoodmanVice President Precinct 4 Craig SmithSecretary Precinct 5 Chuck Murphy Precinct 1 Gary Franklin Precinct 2 BSEACD Data Series Report 2006-1025 October 2006 Barton Springs/Edwards Aquifer Conservation District 1124 Regal Row Austin, Texas BSEACD Data Series Report 2006-1025 iii

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CONTENTS Abstract 1 Introduction 1 Purpose and Scope 1 Well and Data Inventory 3 Water-Level Data 10 Data Collection Methods 10 Measurement Points and Datums 10 Frequency of Water Level Measurements 11 Data Compilation and Quality Assurance 11 Sources of Water Level Fluctuations 12 Barometric Effects 13 Well Completion 13 Acknowledgments 13 References 14 Appendix .... 15 FIGURES Figure 1. General location map showing aquifer hydrologic zones, District boundaries, rivers and creeks, roads, major cities/towns, springs, and other landmarks. Figure 2a-e. Water level hydrographs. TABLES Table 1. Summary of wells and data. Table 2. Source of water-level fluctuations in the Edwards Aquifer. BSEACD Data Series Report 2006-1025 iv

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GROUNDWATER LEVELS IN THE BALCONES FAULT ZONE, HAYS AND TRAVIS COUNTIES, TEXAS, 1937-2005 Brian B. Hunt, P.G. and Brian A. Smith, Ph.D., P.G. ABSTRACT More than 50,000 water-level measurements from 1937 to 2005 in the Balcones Fault Zone of Central Texas were compiled from 49 wells, and one quarry. Data represent water levels from the Edwards, Trinity, and Austin Chalk Aquifers. A simple database was constructed to compile the water-level and well-construction data. The purpose of this report is to provide a foundation for future hydrogeologic investigations. INTRODUCTION Groundwater is an important resource for Texans and constituted nearly 60% of all water used by Texans in 1999 (TWDB, 2002). Aquifers along the Balcones Fault Zone in Central Texas provide an important groundwater resource for industrial, domestic, recreational, and ecological needs. The study area is located along the Balcones Fault Zone of Central Texas within portions of Travis and Hays counties (Figure 1). Water-level data within this report are primarily from wells completed within the Edwards, and to a lesser extent, the Trinity Aquifer. A relatively minor, locally water-bearing unit in the study area is the Austin Chalk. This paper and accompanying database present a compilation of continuous water-level data from groundwater resources in the study area. Groundwater levels provide critical information about the hydrologic relationships of recharge and discharge to storage within an aquifer, and the direction of groundwater flow. Long-term, systematic measurements of water-level data are essential to develop groundwater models and to design, implement, and monitor the effectiveness of groundwater management programs (Taylor and Alley, 2001). This report includes data that numerous agencies have collected over the years: the United States Geological Survey (USGS), Texas Water Development Board (TWDB), Edwards Aquifer Authority (EAA), Hays-Trinity Groundwater Conservation District (HTGCD), San Antonio Water Systems (SAWS), and the Barton Springs/Edwards Aquifer Conservation District (BSEACD). Purpose and Scope This report compiles more than 50,000 water-level measurements made from 1937 to 2005 for 49 wells (and one quarry) completed in the Edwards, Trinity, and Austin Chalk Aquifers. A simple Microsoft Excel-based database was constructed and accompanies this report. The database contains well-completion information and water-level data. The purpose of this report is to provide a foundation for future hydrogeologic investigations and evaluations of water resources in central Texas. The database presented in the report is currently the most comprehensive available for the study area. BSEACD Data Series Report 2006-1025 1

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Figure 1. General well location map showing aquifer hydrologic zones, District boundaries, rivers and creeks, roads, major cities/towns, springs, and other landmarks. BSEACD Data Series Report 2006-1025 2

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WELL AND DATA INVENTORY This report contains tabulation of wells and data summarized in Table 1. More information about the completion and construction of the wells can be found in the accompanying database or in the BSEACD Data Series Report 2006-0818. Table 1. Well and Data Inventory. SWN Well Name Well Owner County DD Lat DD Long Lat/long Source LSD (ft) 1 LSD Source M.P. (ft) 2 TD (ft) 3 Date Drilled Aquifer Code 4 Period of record Data Count 1 5842819 Greenbelt City of Austin Travis 30.26101000 -97.81757000 GPS 680 USGS Quad 1.94 311 1982 218EBFZA 1999 1,974 2 5842911 Bee Caves Bee Caves Properties Travis 30.26861111 -97.78250000 USGS Quad 517 USGS Quad 0.00 135 1920 218EBFZA 1937 to 1982 133 3 5842927 Tx School for Deaf Tx School for Deaf Travis 30.25055600 -97.75361100 USGS Quad 505 COA topo ? 285 1986 218EBFZA 1986 93 4 5842929 Tx School for Deaf Tx School for Deaf Travis 30.25055600 -97.75361100 USGS Quad 505 COA topo ? 561 1986 218EBFZA 1986 95 5 5849406 Slopes of Nutty Brown J. Howeth Hays 30.17833330 -97.96277780 USGS Quad 1015 USGS Quad 1.00 530 1985 218GLRS 1986 31 6 5849706 Radiance Colony Radiance Colony Hays 30.14569444 -97.96701111 GPS 1060 USGS Quad 2.45 1050 1986 218GLRT 2004 to 2005 497 7 5849925 Borheim Trinity City of Austin Hays 30.12594000 -97.90382000 USGS Quad 789.86 Survey (toc) 3.63 1000 1985 218GRHC 1985 538 8 5849926 Borheim Trinity-Edwards Hybrid City of Austin Hays 30.12512778 -97.90510000 USGS Quad 794.24 Survey 0.22 609 1985 218EBFZA 1995 32 9 5850120 HEB TWDB Travis 30.23500000 -97.87305600 USGS Quad 832 USGS Quad 2.30 855 1984 217HSTN 1987 950 10 5850121 Legend Oaks Legend Oaks Home Owners Assoc. Travis 30.22018000 -97.86961000 USGS Quad 830 USGS Quad 2.20 950 1989 218GRLU 2001 999 11 5850205 Allred unknown Travis 30.23138890 -97.80583330 USGS Quad 685 USGS Quad 0.00 265 1887 218EBFZA 1939-1949 56 12 5850212 Sunset City of Sunset Valley Travis 30.22548000 -97.80618000 GPS 674 COA topo 1.70 336 1955 218EBFZA 1997 2,253 13 5850216 Target USGS Travis 30.23222220 -97.79277780 USGS Quad 690 USGS Quad 3.17 582 1978 218EBFZA 1981 1,097 14 5850301 Lovelady Texas Middle School Association Travis 30.21035000 -97.78159000 GPS 654 COA topo 1.35 388 1949 218EBFZA 1948 5,144 15 5850411 Circle C Stratus Development Travis 30.18666670 -97.84916670 GPS 770 USGS Quad 1.50 469 1940 218EBFZA 1978-1997 896 16 5850417 Zumwald City of Austin Travis 30.19536000 -97.84640000 GPS 804 COA Topo 1.70 330 1938 218EBFZA 2001 1,341 17 5850501 Garner L.J. Garner Travis 30.17333330 -97.83055560 USGS Quad 726 USGS Quad 0.00 ? <1958 218EBFZA 1949 to 1958 27 18 5850502 Herndon Shelly Hansen Travis 30.18694444 -97.81416667 USGS Quad 742 USGS Quad 0.00 300 1937 218EBFZA 1949 to 1985 52 19 5850511 Johnson Rodney Johnson Travis 30.17158611 -97.82578611 GPS 699 GPS 1.85 285 1956 218EBFZA 1956 16 20 5850601 TWDB Chalk well H.S. Lawson Travis 30.19861100 -97.77611100 USGS Quad 660 USGS Quad 0.00 25 <1937 211ASTN 1937 237 21 5850702 Charles C.R. Charles Travis 30.14777778 -97.87333333 USGS Quad 765 USGS Quad 0.00 217 1945 218EBFZA 1949 to 1959 36 22 5850704 Marbridge Marbridge Foundation Travis 30.13722220 -97.85583330 USGS Quad 727 USGS Quad 0.70 345 1968 218EBFZA 1968 79 23 5850801 Dowell Caroline Dowell Travis 30.14281000 -97.81076000 GPS 660 USGS Quad 1.50 264 1939 218EBFZA 1941 4,912 24 5857201 Rutherford Mike Rutherford Hays 30.10305560 -97.93722220 USGS Quad 925 USGS Quad 0.50 320 1945 218EBFZA 1950 91 BSEACD Data Series Report 2006-1025 3

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Table 1. Well and Data Inventory. SWN Well Name Well Owner County DD Lat DD Long Lat/long Source LSD (ft)1 LSD Source M.P. (ft) 2 TD (ft) 3 Date Drilled Aquifer Code4 Period of record Data Count 25 5857301 Thames John Thames Hays 30.09388890 -97.89055560 USGS Quad 883.00 Survey 1.10 312 1937 218EBFZA 1937 47 26 5857502 Hoskins City of Austin Hays 30.06634722 -97.94447222 GPS 890 USGS Quad 0.00 346 1963 218EBFZA 1977 287 27 5857509 Onion Creek Lodge Madelyn Uresti Hays 30.07240278 -97.92031111 GPS 781 USGSQuad 0.60 258 1988 218EBFZA 1988 57 28 5857602 Old Onion Creek Lodge Micheal Thames Hays 30.07420833 -97.91579722 GPS 798 GPS 1.00 208 <1975 218EBFZA 1975 to 2002 789 29 5857902 Gregg Paul Gregg Hays 30.00861110 -97.89611110 USGS Quad 822 USGS Quad 0.00 450 <1943 218EBFZA 1943 190 30 5857903 Negley Plum Creek/Negley Ranch Hays 30.03851000 -97.88618000 Survey 826.80 Survey 0.62 400 1943 218EBFZA 1949 2,351 31 5858101 Buda Keith Thornsberry Hays 30.08358000 -97.84263000 Survey 707.84 Survey 1.15 237.5 1907 218EBFZA 1937 5,368 32 5858123 Porter Elizabeth Porter Hays 30.10943000 -97.84173000 GPS 712 GPS 2.80 510 1985 218EBFZA 1994 3,100 33 5858201 Heep Heep Estate Travis 30.10805600 -97.80777800 USGS Quad 700 USGS Quad ? 105 1938 211ASTN 1938-1956 123 34 5858301 United Gas United Gas Pipeline Travis 30.09222220 -97.78944440 USGS Quad 734 USGS Quad ? 703 1943 218EBFZA 1943 477 35 6701303 Old Kyle PWS Edwards Aquifer Authority Hays 29.99000000 -97.87555600 USGS Quad 719.24 Survey 1.10 594 1939 218EBFZA 1959 3,027 36 6701304 Selbera Raynaldo Selbera, Jr. Hays 29.98472200 -97.87638900 USGS Quad 717.55 Survey 0.25 372 1934 218EBFZA 1934 413 37 6701311 Kyle Test Hole #1 San Antonio Water Systems Hays 29.98138900 -97.89138900 USGS Quad 768 USGS Quad ? 810 1997 218EBFZA 1997 75 38 6701809 Knispel A.F. Knispel Hays 29.91191700 -97.92877200 Survey 601.27 Survey ? 34 1937 218EBFZA 1937 4,311 39 6702104 Kyle Test Hole #2 San Antonio Water Systems Hays 29.98279167 -97.87153056 GPS 674 GPS ? 975 1998 218EBFZA 1998 254 40 6702105 Kyle Test Hole #4 San Antonio Water Systems Hays 29.97472200 -97.85722200 USGS Quad 647 USGS Quad ? 970 1998 218EBFZA 1998 29 41 6702106 Kyle Test Hole #3 San Antonio Water Systems Hays 29.97472200 -97.85722200 USGS Quad 678 USGS Quad ? 1100 1998 218EBFZA 1998 50 42 57569CB Camp Ben McCulloch Unknown Hays 30.12960931 -98.01430184 GPS 963 GPS 2.40 360 2002 218TRNT 2002 36 43 58428TW Eye Care Tom Walters Travis 30.26140000 -97.79518056 GPS 632 GPS 0.00 404 <1993 218EBFZA 1993 76 44 58495MH Hills of Texas unknown Hays 30.17986418 -97.94807433 GPS 955 GPS 0.95 840 1996 218TRNT 2001 41 45 58499BQ Borheim Edwards City of Austin Hays 30.12550000 -97.90366000 USGS Quad 787.38 Survey (toc) 0.90 180 2003 218EBFZA 2003 533 46 58499QL BorheimQuarry Lake City of Austin Hays 30.12697222 -97.90738889 USGS Quad 754.57 Survey 0.00 15 n/a 218EBFZA 2002 25 47 58501W2 Brush Country City of Austin Travis 30.22640000 -97.84147000 GPS 742 COA topo 1.45 187 1986 218EBFZA 1999 1,373 48 58573GC Callon Gary or Susan Callon Hays 30.09758056 -97.88685556 GPS 825 GPS 0.00 235 <1994 218EBFZA 2000 1,366 49 58579A Miller Susan Miller Hays 30.03002778 -97.89255556 USGS Quad 835 USGS Quad 2.05 300 <1991 218EBFZA 1991 2,397 50 58584CT Centex Centex Materials Hays 30.06020000 -97.86848000 Survey 734.80 Survey 1.13 206.4 <1994 218EBFZA 1994 2,034 1 Land Surface Datum (LSD) is the elevation in feet above mean seal level. 2 Measurement Point (MP), measured in feet above the LSD. 3 Total Depth (TD) of well in feet. 4 Aquifer code of the Texas Water Development Board. BSEACD Data Series Report 2006-1025 4

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Figure 2a: Water Level Hydrographs400500600700800900100008/04/3508/01/4507/30/5507/27/6507/25/7507/22/8507/20/9507/17/05Elevation of Water Level (ft-msl) 57-56-9CB 58-49-406 58-49-706 58-50-216 58-50-301 58-50-601 58-57-201 58-57-301 58-57-9A 58-58-101 58-58-301 58-49-9QL BSEACD Data Series Report 2006-1025 5

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Figure 2b: Water Level Hydrographs40050060070080090010008/4/19358/1/19457/30/19557/27/19657/25/19757/22/19857/20/19957/17/2005Elevation of Water Level (ft-msl) 58-42-819 58-42-929 58-50-502 58-50-801 58-57-903 58-50-1W2 67-01-809 58-49-926 BSEACD Data Series Report 2006-1025 6

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Figure 2c: Water Level Hydrographs40050060070080090010008/4/358/1/457/30/557/27/657/25/757/22/857/20/957/17/05Elevation of Water Level (ft-msl) 58-42-8TW 58-42-911 58-49-925 58-49-9BQ 58-50-121 58-50-411 58-50-501 58-57-509 58-57-902 67-01-303 58-57-502 BSEACD Data Series Report 2006-1025 7

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Figure 2d: Water Level Hydrographs400500600700800900100008/04/3508/01/4507/30/5507/27/6507/25/7507/22/8507/20/9507/17/05Elevation of Water Level (ft-msl) 58-49-5MH 58-50-120 58-50-205 58-50-212 58-50-417 58-50-511 58-50-702 58-57-3GC 5858123 67-01-304 67-02-106 BSEACD Data Series Report 2006-1025 8

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Figure 2e: Water Level Hydrographs40050060070080090010008/4/19358/1/19457/30/19557/27/19657/25/19757/22/19857/20/19957/17/2005Elevation of Water Level (ft-msl) 58-50-511 58-50-704 58-57-602 58-58-201 67-01-311 67-02-104 67-02-105 58-58-4CT BSEACD Data Series Report 2006-1025 9

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WATER-LEVEL DATA Hydrographs of the data within this report are presented in Figures 2a-e. A simple database accompanying this report contains water-level and well-construction data (see Appendix). The period of record for this report includes continuous data through March 2005, however some wells have data through August 2006. Data Collection Methods Data within this report were collected by a variety of agencies including: TWDB, BSEACD, USGS, EAA, SAWS, and HTGCD. It should be noted that each of these agencies has their own protocols and methods for the collection of data, which in some cases have changed over time. Methods are only briefly discussed in this report and individuals interested in the details of those methods are encouraged to contact the corresponding agencies. Data collection methods employed by the BSEACD are described in Hunt et al. (2004). Water-level data compiled in this report were collected with either manual measurements or with automated recorders. Manual measurements were often made with a steel tape or electric lines (eline). Automated instruments include chart recorders or pressure transducers with data loggers. Manual measurements are periodically made in conjunction with automated instruments for calibration and verification purposes. Manual measurements are generally accurate to within .1 feet. These data are also contained in the report where available and provide quality control and assurance for the automated data. Measurement Points and Datums Water-level measurements are made in reference to a measurement point (MP) at the well head. Commonly the MP corresponds to the top of casing (TOC). The MP or TOC measurement is subtracted from the depth-to-water measurement to reflect a depth from the land surface datum (LSD). LSD is generally defined as the top of the concrete slab around the casing, or from ground level. Data obtained from the TWDB, USGS, EAA and HTGCD are reported as depth from LSD; however, some data may actually be from the TOC. Historic data from the BSEACD were originally reported as depth from TOC (both manual and transducer data), but have been adjusted in this report to reflect the depth from LSD. Depth to water below LSD is a positive value, negative values reflect a level above the LSD, such as flowing artesian wells (see 58-42-927, 58-42-929; 58-50-601). Elevations for LSDs were obtained from USGS topographic maps (10-ft contours), City of Austin topographic maps (2-ft contours), or from surveys. Vertical datums from those maps are either North American Vertical Datum 1929 (NAVD29) or North American Vertical Datum 1988 (NAVD88). Many of the horizontal coordinates were collected with a Global Positioning System (GPS), or by locating on a USGS topographic map, or BSEACD Data Series Report 2006-1025 10

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by survey. Horizontal datums are in World Geodetic System 1984 (WGS84) or North American Datum 1983 (NAD83). Frequency of Water-Level Measurements All the data in this report are considered continuous because there is a significant density of data over a given period of time from a well allowing some inference as to the hydraulic stresses on the aquifer or well. However, a majority of the data are actually periodic in nature with data spanning weeks to years. Data prior to about 1980 consist of periodic manual measurements of this type. After the 1980s, automated data collection systems (chart recorders and pressure transducers with data loggers) were used more frequently within the study area. These automated systems collect data continuously, like chart recorders, or at a high frequency (such as hourly to daily), such as pressure transducers with data loggers. These large datasets have been reduced to daily measurements by the various agencies and may represent an average value for the day, or as in the case of the BSEACD data, represent the maximum elevation (minimum depth) for that day. Accordingly, data from automated recorders do not generally have a time associated with the date. However, many manual measurements do have an associated time. Those with an unknown time are indicated by a 0:00 AM or 1:00 AM in the date column. Data Compilation and Quality Assurance The TWDB database was the source of most of the historical data before 1990. Only data listed as publishable were incorporated into the database. TWDB data are available on their website at: http://www.twdb.state.tx.us/GwRD/waterwell/well_info.asp Additionally, the USGS collected a significant amount of historical data, and those are available via their website or in published reports. After about 1990, agencies such as the EAA, SAWS, BSEACD, and the HTGCD began collecting data from more sites, and more frequently. A systematic quality-assurance review was conducted for this report and database. Automated data from the BSEACD since about 1988 provided the greatest challenge for quality control and assurance. Manual measurements were compiled from field notebooks and were plotted with the automated data for quality control and assurance purposes. All of the information provided is believed to be accurate and reliable; however, the BSEACD assumes no responsibility for any errors or for the use of the information provided. BSEACD makes no guarantees or warranties as to the accuracy, completeness, currency, or suitability of the data provided in this report. All data from agencies other than the BSEACD should be regarded as provisional. BSEACD Data Series Report 2006-1025 11

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SOURCES OF WATER LEVEL FLUCTUATIONS The purpose of this report is to present data without significant interpretations. However, a brief discussion of the factors and hydrologic stresses on the groundwater resources is warranted. Water-level fluctuations represent changes in storage within the aquifer and are caused by hydrologic stresses. Long-term fluctuations in water levels represent changes in storage due to recharge and discharge (Table 2). Fluctuations from drought-of-record conditions to high-flow conditions in the Edwards Aquifer are on the order of 75 and 100 feet in the unconfined and confined portion of the Edwards Aquifer, respectively. Although data from the Trinity Aquifer are more limited, Trinity wells appear to have a similar dynamic range in water-levels, although they vary within specific Trinity units. Table 2. Source of water-level fluctuations in the Edwards Aquifer. Hydrologic Stress Approximate magnitude of fluctuation Comment Long-term Climatic (months to years) up to 100 ft (confined) up to 70 ft (unconfined) Pumping (daily) up to 50 ft (confined) Influenced by nearby large-capacity pumping wells Recharge (daily) up to 15 ft (confined) up to 10 ft (unconfined) Barometric (daily) up to 0.1 ft Confined conditions only Tidal (daily) 0.1-0.01 ft? Needs further study The dynamic nature of water levels in the Edwards Aquifer is a result of triple porosity of the aquifer, with diffuse, fracture, and conduit porosity (Hovorka et al., 1998). The Edwards and to a lesser extent, the Trinity Aquifer, are very heterogenous and anisotropic aquifers. Accordingly, the response of water levels to the various hydrologic stresses can be markedly different for each well site. For example, many wells correlate very well with Barton Springs, such as the Porter Well (58-58-123), which indicates they are heavily influenced by conduit flow. However, the Lovelady well (58-50-301) appears to have a muted response to recharge and is dominated by diffuse flow to the well. Other wells appear to be dominated by conduit flow such as wells 58-50-411 and 58-50-417. The Trinity Aquifer is dominated by diffuse flow; however there is some indication of dynamic water-level responses that could indicate fracture or conduit flow within certain limestone units (see well 58-49-706). Proximity to a pumping well can also influence water levels within a well. Although most of the wells in the database are not located close to actively pumping wells, or are not significantly impacted by their cones of influence, there are some wells that are heavily influenced by pumping, and their water levels can be temporarily lowered by 50 feet from the static level. The Buda (58-58-101) and Dowell monitor wells (58-50-801) are two examples of wells heavily influenced by nearby pumping. Other wells, such as the BSEACD Data Series Report 2006-1025 12

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Porter (58-58-123) and Centex (58-58-4CT) wells also have relatively minor pumping influences, on the order 2 to 3 feet under average conditions. However, these fluctuations are generally discernable on hourly data. It is important to note that the BSEACD collects data hourly with pressure transducers and data loggers, but the daily measurement reported is the maximum elevation for a given day. This method appears to filter out most minor fluctuations due to local pumping effects. Barometric Effects Barometric pressure acts upon the aquifer rock matrix and water levels within a well. Water levels have an inverse relationship to barometric pressure changes and are most commonly observed in confined aquifers because of the hydraulic gradient between the well and the surrounding aquifer. Barometric responses are not commonly observed in wells completed within unconfined aquifers because the pressures are evenly distributed between water levels within a wells and the water table (Domenico and Schwartz, 1990). The barometric efficiency of the Negley well (58-57-903) in the confined portion of the Barton Springs aquifer, and determined from a 2-day period, is 0.67, indicating a good relationship between water-level and barometric changes. BSEACD water-level data after 2002 were collected with non-vented (absolute pressure-transducer) probes. Most data have been compensated for barometric fluctuations unless otherwise noted. WELL COMPLETION Well completion information was obtained from drillers logs, many of which are within the TWDB database. Most wells were drilled as water-supply wells that have been converted into monitoring sites. Most wells have an open borehole completion with diameters of at least 4 to 6 inches. Many wells within the Edwards Aquifer only partially penetrate the entire saturated thickness. Water levels from a partially penetrating well may not be representative of the aquifer as a whole. Wells reported as completed within the Trinity Aquifer are often hybrids of the upper and middle Trinity aquifers. ACKNOWLEDGEMENTS The TWDB, USGS, SAWS, EAA, and HTGCD provided much of the data within this report. Specifically, thanks go to Rob Esquilin (EAA) and Kenneth Davis (HTGCD) for supplying data. BSEACD staff that collected data and contributed to the Districts water-level program include: Stefani Campbell, Joe Beery, Nico Hauwert, Ron Fiesler, Beckie Morris, and Shu Liang. BSEACD Data Series Report 2006-1025 13

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REFERENCES Domenico, P.A., and F.W. Schwartz, 1990, Physical and Chemical Hydrogeology: New York, John Wiley & Sons, 824 p. Hovorka, S., Mace, R., and Collins, E., 1998, Permeability Structure of the Edwards Aquifer, South TexasImplications for Aquifer Management: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 250, 55 p. Hunt, B., B. Smith, S. Helmcamp, and S. Liang., 2004, Groundwater-Level Monitoring Program: Example from the Barton Springs Segment of the Edwards Aquifer, Central Texas: in Proceedings from the 2004 Texas Water Monitoring Congress, Austin, Texas September 15-17, 2004. Taylor, C., and W. Alley, 2001, Ground-Water Level Monitoring and the Importance of Long-Term Water-Level Data. U.S. Geological Survey Circular 1217, Denver Colorado, 68 pp. BSEACD Data Series Report 2006-1025 14

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BSEACD Data Series Report 2006-1025 15 Appendix. Database of groundwater levels in the Balcones Fault Zone, Hays and Travis Counties, Texas, 1937-2005. The compact disk contains a simple Microsof t Excel-based database. It contains a summary worksheet titled: Figure 1-Well & Da ta Summary with an internal hyperlink to each well and corresponding data set. Figur e 2a-e hydrographs are also presented as worksheets in the database.