The hydrogeology and problems of peninsular Florida's water resources - January 3rd, 1976


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The hydrogeology and problems of peninsular Florida's water resources  - January 3rd, 1976

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The hydrogeology and problems of peninsular Florida's water resources - January 3rd, 1976
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Parker, Garald G. (Garald Gordon), 1905-2000
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Aquifers -- Hydrogeology -- Everglades (Fla.) -- Florida ( lcsh )
Hydrology -- Florida -- Biscayne Aquifer (Fla.) ( lcsh )

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University of South Florida
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University of South Florida
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The University of South Florida Libraries believes that the Item is in the Public Domain under the laws of the United States, but a determination was not made as to its copyright status under the copyright laws of other countries. The Item may not be in the Public Domain under the laws of other countries.
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032968560 ( ALEPH )
891343127 ( OCLC )
G16-00636 ( USFLDC DOI )
g16.636 ( USFLDC Handle )

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THE HYDROGEOLOGY AND PROBLEMS OF PENINSULAR FLORIDA'S WATER RESOURCES l_/ BY 2/ GARALD G. PARKER, C.P.G.-l_/ A lecture presented at the Second International Citrus Short Course, University of Florida, Cainsville, Fl. 32611, Oct. 13, 1975. ./ Certi.fied Professional Geologist #691. Consulting Geologist and Hydrologist, Geraghty & Miller, Inc. 3303 Mc Farland Road, Tampa, Fl. 33618.

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Illustrations Figure 1. Fence diagram of the Central Florida area showing the stratigraphic relations among the Floridan Aquifer, the confining beds (the Floridan Aquiclude) and the shallow aquifer. Figure 2. Idealized hydrogeologic cross section in western Hardee and De Soto Counties, Florida. Figure 3. Map of circular areas surrounding each large well field of the Tampa Bay Region showing areas required to produce recharge needed to supply minimum and maximum pumping rates shown. Figure 4. Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1975. Features shown include: Potentiometric contours; the three principal artesian highs; regional direction of ground-water flow through the Floridan Aquifer; and the Peninsular Florida Hydrologic Divide. Hatchured lines are closed contours outlining areas of internal flow. Figure 5 : Potentiometric map of Southwest Florida Water Management District and surrounding lands for Sept., 1949. Figure 6. Potentiometric map of Southwest Florida Water Management District and surrounding lands for Jan., 1964. Figure 7 . Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1969. Figure 8. Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1971. Figure 9. Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1973. Figure 10. Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1974 Figure 11. Potentiometric map of Southwest Florida Water Management District and surrounding lands for May, 1975.

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THE HYDROGEOLOGY AND PROBLEMS OF PENINSULAR FLORIDA'S WATER RESOURCES BY GARALD G. PARKER, C.P.G. The Floridan Aquifer and the Water Crop Underlying all of Florida and extending northward into Alabama, Georgia and South Carolina is one of the world's largest (82,000 mi 2 ) and most prolifically-yielding ground-water reservoirs, the Floridan Aquifer (Parker et al, 1955). Some of the wells yield upward of 8,000 gallons per minute, but more commonly yields of 1,000 to 2,000 gallons per minute are reported. Composed chiefly of limestone and dolostone (Fig. 1), with increasing quantities of evaporites (gypsum, anhydrite and halite) toward the base, the Floridan Aquifer is the source of about 90 per cent of the water withdrawn for human use in the Florida Peninsula north of Lake Okeechobee. South of that lake the Floridan Aquifer is deeply buried (depths of 600 to 800 feet along Florida's Gold Coast) and contains only saline water. In fact, most of the tier of eastern counties lying along the Atlantic Coast north of Lake Okeechobee to Jacksonville and beyond is also underlain by non-potable salty water in the Floridan Aquifer (Klein, 1971). Everywhere at some depth, the Floridan Aquifer either contains or is underlain by brackish to salty water, the deeper parts of it consisting of brines many times saltier than the ocean. Only sparsely used at present, such brackish water in the future may be utilized through desalination processes to produce potable water supply. Techniques are known and currently utilized in about a dozen Florida localities to produce potable water from the brackish ground water

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of the Floridan Aquifer. Economics will determine the future extent of such desalinatio~ projects. Even now, in some areas, it is cheaper to desalinate brackish ground water than to develop fresh water many miles distant and import it through lengthy pipelines. Currently, either fresh or brackish ground-water can be developed at the well head or pump orifice for less than ten cents a thousand gallons but to desalinate brackish water costs an additional 50 cents to $1.00 a thousand gallons, depending chiefly upon the salinity and the process used. The aquifer ranges in thickness from about 500 feet in Citrus and Levy Counties to about 2,000 feet in Duval County. Leve (1968) indicates that the aquifer is deeper than 2,200 feet in Nassau County with a fresh-water thickness of about 1,600 feet. In Central Florida the Floridan Aquifer extends to depths of 2,000 feet or more (Pride et al, 1962) and may be filled with fresh water to about 2,500 feet in some areas (Fig. 2). Kohout (1965, 1967) indicates that the Floridan is about 2,500 feet thick in the Miami area where he included the "Boulder Zone", a cavernous, caving (when drilled) dolostone containing salt water, in the Floridan Aquifer. Recharge to the Floridan ranges from about 250,000 gpd/mi2 (gallons per day per square mile) to more that 1 mgd/mi 2 (million gallons per day per square mile) in areas where recharge takes place. In all of those areas of the state where the potentiometric surface of the Floridan Aquifer is higher than the land surface, no recharge takes place. The rate of recharge is largely dependent upon the, permeability of geologic materials overlying the Floridan (where it is at or very close to the land surface) and of the overlying materials where the Floridan is buried more or less deeply. In the west-central Gulf Coastal area where precipitation (P) averages about 52 inches a year, direct recharge from precipitation averages about 12 to 13 inches per square mile, or about 572,000 gpd/mi2 to 619,700 gpd/mi2 • With 2

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an average measured runoff (R) of 14 inches per year, plus an estimated 1 inch of ground-water discharge directly to the Gulf of Mexico (Cherry et al, 1970), this leaves only 2 to 3 inches of direct, overland runoff contributing to streamflow. Thus, about 77 to 80 per cent of the total discharge of 15 inches is derived from the aquifer discharge to the streams that drain the area. The rest of the long-term P value of 52 inches, about 38 inches per year, is lost to evapotranspiration (Et). The water budget equation for these relationships is: P(52") = R(l5") + Et(37"). Inasmuch as R represents the only significantly manageable part of the water-budget equation it also sets the upper limit of developmental water supplies. If we were to take all of R(l5") for consumptive use we could derive approximately 715,000 gpd/mi2 . This is the potential water crop. But if we did, the streams would cease flowing, lakes and swamps would dry up and the lowered water table _would no longer sustain soil moisture during dry periods for most plants. This is unthinkable, so we must not take all of R (the potential water crop) but something less, the available water crop. This may be only 1/3 or 1/4 of the potential water crop, thus our available water crop becomes about 5" (238,360 gpd/mi2 ) or 3.75" (178,770 gpd/mi2). The Biscayne Aquifer and the Water Crop The southeastern Florida Gold Coast is chiefly dependent for its water supply upon the Biscayne Aquifer, a wedge-shaped ground-water reservoir about 200 feet to 300 feet thick along the Atlantic Coast and thinning to a feather edge along the western margin of the Everglades where the glades abut against the higher lands of the Big Cypress and the Devil's Garden (Parker et al, 1955; Parker, 1974). 3

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The Biscayne Aquifer is one of the most highly permeable aquifers in the world ranking with clean, well-sorted gravel in its capacity of transmitting water under water-table conditions. However, the aquifer has been badly abused and mismanaged in the past, thus leading, among others, to serious salt-water encroachment problems that are now nearing controlled management (Leach et al, 1972). Many 6-inch diameter wells yield 1,000 gpm or more with less than a foot of draw-down. Larger wells, 16 to 20 inches in diameter, yield 3,000 to 4,000 gpm. The top of the Biscayne Aquifer is generally at or very close to the land surface with very little soil cover in Dade County; to the north a thickening cover of permeable sand mantles the aquifer. Thus, recharge from precipitation is direct and the water table rises quickly in response to recharge from rains. Parker and Warren (Parker et al, 1955) have shown that, of an average of 60 inches annual average precipitation in the Miami area, about 38 inches actually recharges the aquifer annually, thus 22 inches is lost to Et before reaching the water table. But 25 inches is discharged from the aquifer by seepage to canals and Biscayne Bay, thus 13 inches is discharged to Et directly from the water table. Adding the 22-inch loss of rain not reaching the water table to the 13-inch loss to Et from the water table, we get a total Et loss of 35 inches • . In other areas, such as Kendall and Homestead, 35 to 40 inches of P actually reach the water table, not greatly different from that at Miami. But of this amount, about 15 to 20 inches is lost by ground-water discharge to canals and Biscayne Bay while 20 to 25 inches is directly lost to Et from the water table. Thus, in the Kendall and Homestead areas, total Et losses run about 40 to 45 inches a year. Looking at these figures in terms of the potential water crop, we find for the Miami area about 25 inches per mi 2 per year (60"P -35"Et); for 4

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the Kendall area, 20 inches per year per mi2 (60"P -40"Et); and for the Homestead area, 15 inches per year per mi 2 (60"P -45"Et). In terms of gallons these figures translate to 1,191,781 gpd/mi2 for the Miami area; 1,000,096 for Kendall; and 715,068 for Homestead. These values are generally higher than or equal to those of the Tampa Bay region where the potential water crop is about 715,069 gpd/068 gpd/mi2 (Parker, 1975b). The available water crop of the Gold Coast area is generally higher than that of the Floridan Aquifer in Central Florida. This is because of the normally much more rapid and greater direct recharge to the Biscayne Aquifer than to the Floridan, and to the additional water transmitted from the Everglades by the controlled canals and the three huge water-conservation areas owned ,and operated by the Central and South Flood Control District (Leach et al, 1970). As one example, the Hialeah-Miami Springs Well Field now obtains, at times, up to 90 per cent of its water by seepage out of the sides and bottom of the Miami Canal. This canal, in turn, derives most of its water from storage in C&SFFCD's Conservation Area No. 3. With the tremendous storage available in the three big conservation areas and the large amounts of ground-water seepage eastward, from them into the Biscayne Aquifer, the well-regulated system of canals and huge, high-capacity .pumps that are capable of moving tremendous quantities of water from places of excess to places of deficit, water management in the Gold Coast is much simpler and more effective than elsewhere in Florida. Although problems of water supply still occur there, these problems are more related to management problems (which are rapidly being overcome) than to a dearth of available water in the KLOE (Kissimmee Lake Okeechobee -Everglades) system (Parker, 1974). Because of these facts, the current paper will delve no further into the Gold Coast as an area of critical water problems. Such problems exist mostly in the South-5

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west Florida Water Management District and in the adjoining, temporary, Ridge and Lower Gulf Coast Water Management District. Critical Water-Problem Areas of SWFWMD. There are currently defined three principle water-problem areas: (1) The coastal strip of salt-water encroachment (Fig. 3); (2) the big well fields of the Tampa Bay area (Fig. 3); and (3) the areas of large drawdown of the aquifer water levels as shown in Figure 4 by the hatchured contours. Each of these three proble111areas is distressed either by overdevelopment of the water resources for water-supply uses or a combination of large water-supply development with tidal canals and ditches which result in salt-water encroachment. Let us look at each of these. Coastal Strip of Salt-Water Encroachment Extending along the Gulf Coast from Lee County northward is a coastal strip of varying width containing an encroaching wedge of salt water. The northern part of this strip, from Tampa northward to Citrus County, has been mapped by the U.S. Geol~gical Survey (Cherry et al, 1970; Reichenbaugh, 1972). A part of this mapping, which will give an idea of the width and general inland extent of the salt-wate~ wedge from the Gulf shore, is shown in Fig. 3. The inland edge of the encroachingsalt-water edge is marked by a heavy dashed line indicating the place at which, in 1969, salt water of 250 mg/1 (milligrams_ per liter) occur~ed at a depth of 100 feet below msl (mean sea level). Below this depth the chloride content increases steadily with increasing depth. Likewise, chloride content increases seaward until, at or close to the shoreline, even at very shallow depths, chloride in the ground water equals that of the waters of the 6

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Gulf of Mexico (about 20,000 mg/1). Southward from Tampa the U. S. Geologic.al Survey has not completed its mapping of the encroaching wedge of salt water, but complaints of coastal residents in the coastal strip of western Hillsborough, Manatee and Sarasota Counties indicate that wells formerly producing fresh water now have become salty. The phenomenon of salt-water encroachment, its causes and controls are too well known to require a comprehensive explanation here. For such information readers are referred to Stringfield (1933), Parker (1955), Parker et al (1955) and Reichenbaugh (1972). Suffice it to say that, in a coastal area of freely permeable materials, for each foot that the water table averages one foot above sea level it will be 40 feet down to the salt water contact. Thus, where the water level averages 2 feet above msl it will be about 2 x 40 feet, or 80 feet to salt water and where the water table stands 10 feet above msl it will be 10 x 40 feet or 400 feet to salt water. Thus, when water levels in a coastal area are lowered below their average levels in the past, the natural equilibrium between the overlying lighter, fresh water and the denser, heavier underlying salt water becomes upset and Nature goes about her implacable way of restoring a balance. This causes the salt-water wedge to move inland and, in so doing, the salt-water contact with the fresh water rises. Over the years since white men entered Florida there has been as obsession with draining the swamps and marshes to "reclaim" the land, or to build new water-front homes, or dredge natural coastal stream channels deeper for navigation or other purposes, such as flood control. The result is the same, no matter what the purpose salt-water encroachment. In addition to the drainage and its lowering of water levels, the development of water supply wells in the coastal zone especially has had its impact. Every 7

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well when discharging, whether by artesian pressure or by pumping, lowers the water level in a generally circular area surrounding it. This lowering takes the form of an inverted cone with the greatest lowering of levels at the well itself and the least amount of lowering at some distance away. Hydrologists call this lowered water-level condition around a discharging well or spring a cone-of-depression. When two or more wells are drilled too closely together their cones-of-development overlap, thus producing a single larger and deeper cone-of-depression. Such conditions have happened on a larger scale where municipal, industrial or agricultural wells are crowded too closely together, thus resulting in largearea lowering of the water table or of the potentiometric surface or both. An example of this is shown in Fig. 3 where the big municipal well fields of St. Petersburg and Pinellas have been developed too closely together. More will be said of this in a subsequent section. The progressive lowering of the potentiometric surface with man's development of the west costal region is shown in a series of potentiometric maps of the SWFWMD and surrounding lands, Figures 4 through .l l. A potentiometric map of the Floridan Aquifer shows, by means of contours, the height to which water rises in artesian wells penetrating the rocks of the aquifer for the time during which the water level in the wells was measured. Such a map has many uses. By drawing arrows that cross contours at right angles and proceeding to the next lower contours in the shortest distance possible (as in Fig. 4) one can discern the directions of regional ground-water flow and determine where water comes from and where it goes. 8

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One can also discover the shape of the potentiometric surface and note that there are "highs" and "lows", with ground water flowing away from the highs toward the lows. Three large and prominent highs dominate the potentiometric surface of the Floridan Aquifer in the Floridan Peninsula: (1) The Green Swamp High; (2) the Pasco High; and (3) the Putnam Hall High. From each of these elemental hydrologic eatures ground water continuously flows centripetally outward in all directions indicating continuous recharge from rainfall that is required to sustain this continuous outflow. Another very important hydrologic feature of note is'the Peninsular Florida Hydrologic Divide (Parker, 1975a). No ground-water flow crosses this divide and, except for the St. Johns in its tidal estuary near Palatka, no surface stream of any consequence crosses it. Thus, for our water supplies in peninsular Florida, we are totally dependant upon precipitation that falls on the land south of the Peninsular Florida Hydrologic Divide. No mysterious subterranean streams from the north flow under or over this divide. A glance at the Putnam Hall High shows the flow pattern with all flow arrows pointing away from the divide. But back to the coastal zone of salt-water encroachment. A comparison of potentiometric contours in Figures 5 through 11 shows that, north of Pinellas Co~nty, little apparent change has taken place since 1949. The contours show only a mile or more of eastward migration. Even this small amount, however, involving a lowering of coastal water levels up to 5 feet on the average, has been enough to cause the salt-water encroachment that brought about the loss of the St. Petersburg and Tampa Well fields in the late 1920's and the gradual salting of the New Port Richey well field beginning in the 1960's. Additionally, in the urbanizing coastal strip from Pinellas County northward into Hernando County, hundreds of private wells have turned salty, especially since 1969 when building, dredging and filling on 9

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low lands west of US 19 began on a large scale, particularly in Pasco County. In the area from Tampa southward the change of potentiometric contour conditions has been much more notable and hydrologically important. Perhaps the best way to see this change is to examine the change in location of particular contours, such as the 20-foot contour. The 1949 map shows it disappearing into the Gulf west of Bradenton. Presumably it turned southward paralleling the shoreline at some distance seaward. Stringfield (1933) found that water levels of artesian wells on the offshore islands of Sarasota County stood at 25 feet or more in the early 1930's. Thus the 20-foot contour had to be somewhere seaward of these islands in those early days. Gradually, as one examines subsequent maps, the 20-foot contour is noted to be farther and farther inland. The most notable advance is indicated on the 1971 map (Fig. 8). Between May, 1969 and May, 1971 this 20-foot contour moved inland about 25 miles, a greatly accelerated rate compared with that on previous maps. Now compare this 20-foot contour of 1971 (Fig. 8), with that of 1975 (Fig. 11). The 20-foot contour has advanced inland another 18 miles. And, in the coastal region (this shows up best on Fig. 11), a huge cone-of-depression bounded by the 5-foot potentiometric contour surrounds a greatly depressed area with water levels reaching ten feet below sea level in some places as much as 37 miles from the shore. These conditions are an open invitation for salt-water encroachment to occur. Fortunately, these May conditions of greatly lowered water levels do not persist year arounrl. Once the rainy season sets in and irrigators turn off their big pumps, water levels rise once more, near the coast only a few feet and inland, in central and eastern Manatee County and southern Hardee as much as 30 or 35 feet. But over the years, both high and low seasonal levels show a downward trend that is most accentuated inland (Kaufman and Dion, 1968; Stewart, J.W. et al, 1971). 10

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A crisis situation has not developed yet, but if this trend of downward dropping water levels continues on an ever-expandingarealscale (as exemplified by Fig. 11), a crisis can develop and will be evidenced first by increasing salinity of water-supply wells nearer the coast; already salty water has appeared in the vicinity of the New Riverview Well Field (Hillsborough County), Figure 3. The situation demands careful and accurate monitoring because once salt water has invaded the aquifer it may take many years --if ever--to get it out again. The worst of this situation is that it need not occur at all if only local water-users, particularly irrigators, would use only the water actually needed by their crops or pastures. In the area of concern, there are literally hundreds of large abandoned, irrigation wells flowing to waste year in and year out and wasting billions of gallons yearly. In doing so these wild-flowing wells not only lower the water level for miles around but also create conditions that invite salt-water encroachment. Another reprehensible practice is the wastage of huge volumes of artesian water by over-irrigation. In this area of large coastal drawdown, chiefly in southern Hillsborough, Manatee and northern Sarasota Counties, (Fig. 11) there are no large ..men1lfat0f!ttring plett.ts or ~i~y well fields, but there are hundreds of large irrigation wells. Thes~e in production during the irrigation season from about 1,000 to 5,000 gpm produces 7.2 mgd,at which and a few ,run even higher. A 5,0~ 00 gpm well . , frrrJa 3-month irrigation seaso 648 million ~be pump~ However, as no records are kept of the pumpage, its total quantity is not known nor is it known over what period of time during the irrigation season the pumping is done. It reminds me of the young man who inherited a fortune from a deceased relative but spent his money carelessly and kept no account of his expenditures. It wasn ' t long before he had exhausted his inheritance and was dead broke. Counties, municipalities and even Water Manage-11

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ment Di~tricts can do this too --if care is not taken to see to it that proper management practices are diligently followed in their care and use of our water resources. During the irrigation season of 1974, chiefly January through May, it was a common sight in Manatee County . to see furrow-and-ditch irrigation systems with both ditches and furrows running full of water and, at the lower ends of the to fill the roadside ditches full /c fields, water pouring off as wasted tai~ater v to overflowing. Such ta~ater runoff is not only direct waste of the irrigato~•sP money but a waste of our most precious natural resource profligate waste of water would not be tolerated in New our water. Such Mexico, Arizona,/._ Colo-rada, Utah and other lands of the arid west. Nor should it be tolerated here. Irrigation water should be picked up from sumps at the lower ends of irrigated fields and returned to the upper ends for recycling, thus greatly reducing pumpage from the aquifer. Beginning in 1964, with the large increase in ground-water pumpage to supply both a greatly expanding phosphate industry in the Central Florida Phosphate District (Fountain and Zellars, 1974) and a rapidly expanding citrus, vegetable and improved pasture-irrigation agribusiness, hundreds of new large wells were drilled and pumped. By 1970 total pumpage from the southern Polk --northern Hardee Counties area, according to S. Lee Cawley (unpublished SWFWMD records, 1974), amounted to about 250 mgd for citrus (chiefly); 350 mgd for phosphate mining and milling; and 50 mgd for all other purpose~ amounting to grand total of about 650 mgd. This is about 13 times as much water as is required by either Tampa's or St. Petersburg's municipal water-supply systems and resulted, as time went on, in the development of a large area of potentiometric drawdown centering in the phosphate district south of Bartow. It began showing up first on the 1964 potentiometric map (Fig. 6) as a greatly widened area, mostly in southern Polk 12

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County, between the 70-and SO-foot contours. Water from the Green Swamp High (Fig. 4) could still flow, though very slowly, to the southwest and on into southeastern Hillsborough and eastern Manatee Counties, but at a greatly retarded rate. Thus, for the first time ever, ground-water flow into these two counties was diminished throughground-waterdevelopments in adjacent counties to the east. Figure 7 (1967) shows a SO-foot closed contour occupying the phosphate district drawdown area, and. both the 6O-foot and 7O-foot contours were squeezed to the east and northeast where, in 1964, the 8O-foot and 9O-foot contours had existed. The development of this sump, for the first time ever, cut off the historic Green Swamp flow to the coastal areas of southern Hillsborough, Manatee and Sarasota Counties. This ground-water flow cutoff, first occurring in 1969, created a shortage of inflow and thus, even had irrigation use of water in the coastal counties remained the same in subsequent years as it had been prior t9 1969, the cutoff helped create much greater drawdowns in the coastal agricultural areas than otherwise would have occurred. Because Manatee and Sarasota Counties were not a part of the SWFWMD and had no hydrologic staff or consulting hydrologists to keep track of what was happening to their water supplies, the developing conditions of spreading _ground-water lowering was not realized until the author recognized the situation ~US<'iShG from studies/in the surrounding counties in late ar7i1!ce~ 1973. Even yet, no on e know how much .water is being pumped annually in Manatee and Sarasota County --it can only be estimated. Therefore, precise analyses of the situation still cannot be derived from existing data. The best information available is from the U.S. Geological Survey potentiometric maps and related water-level data which only tell us the symptoms of the disease, not exactly what the causes are. We know that more water is being taken out of the Floridan Aquifer than Nature, in a 13

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given period of time, can put back in. We have the gut feeling that, were the water not wasted on such a colossal scale as seems evident, there would be enough water for all real needs. But intelligent use and conservation of the water supply is greatly needed. The situation is urgent and crying for assistance. Detailed studies of the hydrogeology of both Manatee and Sarasota Counties are direly needed, as are comprehensive studies of the water use and quantities of water actually required. The Ridge and Lower Gulf Water Management District should underwrite a full-scale, comprehensive cooperative study with the U.S. Geological Survey to gain the information needed to handle this problem properly. The same kind of study is needed for Manatee and Sarasota Counties as the SWFWMD has had with the U.S. Geological Survey for Hardee and De Soto Counties (Wilson, 1975). The Big Well Fields of the Tampa Bay Area A classic case of inadequate well-field design and management exists in the Tampa Bay area. No hydrologist in his right mind would have designed and located the existing well fields where they now are, nor would he have prepared pumpin~ schedules such as have been utilized in recent years. In the first place, the well fields are too close together. In the second place they have been pumped too heavily. Figure 3 is a map of the big well fields area and shows by scale drawings, the location of each well field, the area of land held (vertically-lined inner circle) and the areas required to furnish recharge sufficient to supply minimum and maximum pumpage shown. Let us take, for example , Pinellas County's Eldridge-Wilde well field. The inner, vertically-lined circle shows 2.80 mi 2 in the well field. The next circle, dotted, shows that when the well field is producing

PAGE 17

50 mgd an area of almost 77 mi 2 is required to produce from recharge the pumpage taken out. SWFWMD's water crop value of 640,000 gpd/mi2 was used to calculate the area needed for recharge to supply any given pumpage. It doesn't take a highly trained and widely experienced hydrologist to understand why the "water-war" between Hillsborough, Pinellas and Pasco Counties developed, or why, even in the face of the severe drought the area has under since 1961, shallow wells in this area have gone dry, lake levels have fallen and streams, such as Brooker Creek which flow westward to Lake Tarpon through the southern parts of the circles of influence of St. Pete's Sec. 21, St. Pete's Cosme-Odessa and Pinellas County's Eldridge-Wilde well fields, should have had its average flow about halved since 1964. Had SWFWMD (Regulatory) been in existence when these well fields were being planned, there is no doubt that the well fields would not be where they now are. Each would have been located sufficiently far apart that no one well field's 4rawdown would have overlapped that of any other. The knowledge required to make these determinations of well-field spacings has existed since Theis' non-equilibrium formula for evaluating effects of a pumping well was published in 1935, yet these fields and, for that matter, almost all other large well developments in Florida until very recent times have been developed without a suitable hydrologic analysis having been made of the effects that the new development would have on adjacent wells, streams or the environment. To my knowledge, the first places in Florida where such evaluations were made was under the author's direction in the Miami area in the spring of 1947 (Parker et al, 1955). The new Miami well fields were so planned that no interference with another would occur, nor would . salt-water encroachment result, nor would nearby streams or canals be harmfully affected. The samekindsof analyses are now being made under SWFWMD's direction not only for new well fields but for 15

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any large scale diversion of g~Qtlndor surface water within the District that might have potential deleterous effects either upon a neighbor's supply or upon the environment. I wouldexpectno more improper well-field locations ever be made in SWFWMD in the future. And the same conclusions may be reached regarding water-supply developments in the coastal area of salt-water encroachment and in those interior areas of overdraft, such as in the Central Florida Phosphate District. With proper application of hydrogeologic principles the maximum water supplies for municipalities, industry and agriculture can be developed without harm to the resource, the environment or prior users. Nature gives peninsular Florida a larger supply of rain and natural recharge than she gives most places elsewhere on earth. All we need to do to enjoy these blessings is the intelligent management of water and related land resources. Most of the "messes" we now suffer have developed without an understanding over-view of the requirements of good water-and-land management. We have these understandings now and, given an intelligent use of expertise and powers of the several regional Water Management Districts and the West Coast Regional Water Supply Authority, and, with the assistance of competent consulting hydrologists to guide the development of the resources, we need not repeat the errors of the past. We can, if we will, live within our individual and regional water crops and still have enough water to meet the needs of all. But, if we continue our careless and wasteful ways of the past, our most precious natural resource, our • water supplies, can be needlessly ruined. 16

PAGE 19

References Cherry, R.N., Stewart, J.W. and Mann, J.A., 1970, General hydrology of the Middle-Gulf Area, Florida: Fla. Bur. of Geol. Rep't. of Inv. No. 56, 95p., Tallahassee, Fl. Fountain, R.C. and Zellars, M.E._, 1972, Program for ore control in the Central Florida Phosphate District, in Proc. Seventh Forum on Geology of Industrial Minerals, Fla. Bur. of Geol. Spec. Pub. No. 17, p. 187-193, Tampa, Fl. Kaufman, M.I. and Dion, N.P., 1968, Ground-water resources data of Charlotte, De Soto and Hardee Counties, Florida: Fla. Div. of Geol. Info. Circ. No. 53, Tallahassee, Fl. Klein, Howard, 1971, Depth to base of potable water in the Floridan Aquifer: Fla. Bur. Geol., Map Series No. 42. Kohout, F.A., 1965, A hypothesis concerning cyclic flow of salt-water related to geothermal heating in the Floridan Aquifer: New York Acad. Sci. Trans., Ser. 2, v. 28. Kohout, F.A., 1967, Ground-water and the geothermal regime of the Floridan . Plateau: Gulf Coast Geol. Societies, v. 17, p. 339-354. Leach, S.D., Klein, H. and Hampton, E.R., 1970, Hydrologic effects of water control and management of southeastern Florida: Fla. Bur. Geol. Rep't. of Inv. No. 60, 115p., Tallahassee, Fl. Leve, G.W., 1966, Ground water in Duval and Nassau Counties, Florida: Fla. Bur. Geol., Map Series No. 43. Parker, Garald G., 1955, The encroachment of salt water into fresh, in Water, the Yearbook of Agriculture, 84th Congress, 1st Session, House Docu;;nt No. 32, P. 615-625; 732. Parker, Garald G., 1974, Hydrology of the pre-drainage system of the Everglades in southern Florida in Environments of South Florida, present and _past: Miami Geol. Soc. Memoir No. 2, p. 18-27. Parker, Garald G., 1975a, On the hydrogeology of the Southwest Florida Water Management District, in Hydrogeology of West-Central Florida: Southeastern Geol. Soc. Puhl. No. 17, 19th Field Conf., Tampa, Fl. p. 2-32. Parker, Garald G. 1975b, Water and water problems in the Southwest Florida Water Management District and some possible solutions: Am. Water Resources Assn. Bull., v. 11, No. 1, p. 1-20, Minneapolis, Minn. Parker, Garald G., Ferguson, G.E., Love , S.K. and others, 1955 , Water resources of southeastern Florida with special reference to the geology and ground water of the Miami area: U.S. Geol. Survey Water-Supply Paper 1255, 965p., Washington, D.C. 17

PAGE 20

Pride, R.W., Meyer, F.W. and Cherry, R.N., 1966, Hydrology of the Green Swamp area in central Florida: Fla. Bur. of Geol. Rep't. of Inv. No. 42, 137p., Tallahassee, Fl. Reichenbaugh, R.C., 1972, Sea-water intrusion in the upper part of the Floridan Aquifer in coastal Pasco County, Florida, 1969: Fla. Bur. of Geol., Map Series No. 47, Tallahassee. Stewart, J.W., Mills, L.R., Knochenmus, D.D. and Faulkner, G.L., 1971, Potentiometric surface and areas of artesian flow, May, 1969, and change of potentiometric surface 1964 to 1969, Floridan Aquifer, Southwest Florida Water Management District, Florida: U.S. Geol. Survey Hydrologic Atlas, HA-440, Washington, D.C. Stringfield, V.T., 1933, Ground-water resources of Sarasota County, Florida: Fl. Geol. Survey 23rd-24th Annual Rep't. p. 167-177, Tallahassee, Fl. Theis, C.V., 1935, The relation between the lowering of the piezometric surface and the rate and direction of discharge of a well using ground-water storage: Am. Geophys. Union Trans., Pt. 2, p. 519-524. Wilson, W.E., 1975, Ground-water resources of De Soto and Hardee Counties, Florida: U.S. Geol. Survey Open File Report 75-248, Tallahassee,Fl. GGP:cp:dp 01-03-76 18

PAGE 21

c:,. 'I> LM~_)h-~ '""' . 0 \\ -~ EX PLANATIOlf I.A. IHALI.OW AOOll'III COHflNINO HDI f.A. fLORIDAN AOUlfEII u PI.EIITOCUIE I CHOCTAWH A TCHEE Ii!!:] CALOOL\KATCHH S.A. STAGE D IUNDlfFUIENTIAUDl f :~~~Ff C) ALACKIA fORWATION C I . STAGE l rZJ HAWTHORN fACIEt d TAMPA f ST. IAANMIATIOOI GROUP IE ••LLIITON fORWATION F A . tZ] INOLII fOAIIATION _J_ AVON PAIOK LIMESTONE Scale in 12 Regional Location I 20

PAGE 22

500 2500 Idealized Hydrogeologic Cross Section, Western Hardee & De Soto Counties SHALLOW AQUIFE R I CONF l""""C l.OE8 SECONDARY AQUIFEll I CONFINING LAYE• H AWTt4O A N f(>A 1,,u . T IOH BASAL l ltr.l(STONE CAVERN S Y STEM INOT TO $CAL) a: ... .. 5 Q ii: 0 ... ... FJ6-2

PAGE 23

Jj REPRESENTS AREA IN WELL FIELD OWNERSHIP I;:::;:! REPRESENTS AREA TOTALLY D'E WATERED OF AVERAGE DAILY RECHARGE WITH PLANNED MINIMUM PUMPAGERATES rn REPRESENTS AREA TOTALLY DEWATERED OF AVERAGE DAILY RECHARGE WITH PLAN NED MAXIMUM PUMPAGE RATES J / 250 MPG/L CHLORIDE I 30 mgd [ AT 100 FT. MSL ,' 46.15 mi2 ' ( USES-MAY, 1969) I 15 mgd / 23.07 mi2 T. PETE PINELLA COUNTY ELDRIDGE WILDE 50 mgd 76.96 ml 2 ST. .PEt f I I I . , \ cou RIVERVIEW HILLSB~ COUNT KIN S POI =~-A. 1.49 mi2 15 mgd . :~+--23.07. rrii ..4-l----'~ 3 0 mg d 46.15mi~ . H. F. D. A. 40 mgd1 61.53mi S~N •. 7.69 ml2 i g . ~ MAP OF CIRCULAR AREAS SURROUNDING EACH WELL FIELD 1\LCULATED TO BE REQUIRED TO PRODUCE RECHARGE NEEDED TO ' IPPI Y Mll\JIMIJM R MAXlMIJM PllMPING RATF~ SHOWN 02-14-7

PAGE 24

+ Potentiometric Surface of Floridan Aquifer for May, 1975 Showing the Green Swamp, Putnam Hall, and Pasco Highs and the Peninsular Florida Hydrologic Divide ADAPTED FROM U . S. GEOLOGICAL SURVEY 0 t.l -EXPLANATION ..,.. --SOUTHWEST FLORIDA WATER O • MANAGEMENT DISTRICT BOUNDARY 10_... POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r ._, • 0 LEE ea' " Jo, . ff' LAG ER 0 GLADES --r--+

PAGE 25

Potentiometric Surface of Floridan Aquifer for Sept.,194 ADAPTED FROM U.S. GEOLOGICAL SURVEY EXPLANATION SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10-POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYOROLOGIC 01 VIOE SCALI IN MILEI ,.... -..., • 0 11 I HENDRY

PAGE 26

ADAPTED FROM U.S. GEOLOGICAL SURVEY EXPLANATION ---SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10_... P0TENTIOMETRIC SURFACE CONTOUR ~-PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCAlE IN Mll(S r--i • 0 I ,OS CEOLA \J \ \ ... -r---I l !. HENDRY

PAGE 27

Potentiometric Surface of Floridan Aquifer for May, 1969 ADAPTED FROM U.S. GEOLOGICAL SURVEY EXPLANATION ..,.. SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10__... POTENTIOMETRIC SURFACE C()NTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE I SCALE IN MILEI r• • . ~ 11 ' ...... GLADES -t--I LEE HENDRY

PAGE 28

Potentiometric Surface of Floridan Aquifer for May. 1971 ADAPTED FROM U.S. GEOLOGICAL SURVEY EXPLANATION ..,.. --SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10-POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DI VIOE SCALE IN MILH r-, "9 • . 0 11 lf GLADES --r---I LEE HENDRY

PAGE 29

' . I '\. LO.A LAS~YET , Cl~~--\ 5' JOHNS RIST' I ?UT~ ~ -Potentiometric Surface of Floridan Aquifer for May, 1973 ADAPTED FROM U.S. GEOLOGICAL SURVEY ST PH EXPLANATION U"". SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10---:" POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DI VIOE SCALE IN MILES r • 0 ti \ LAGLEA L. I A GLADES ... --r---I I HENDRY

PAGE 30

7 D Potentiometric Surface of Floridan Aquifer for May,1974 ADAPTED FROM U .S. GEOLOGICAL SURVEY EXPLANATION SOUTHWEST FLORIDA WATER . O MANAGEMENT DISTRICT BOUNDARY . . 10-POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DI VICE SCALE IN MllES r -..., ,. 0 11 HIGHLANDS GLADES --t --I LEE HENDRY

PAGE 31

-.------'--. -----Potentiometric Surface of Floridan Aquifer for May, 1975 ADAPTED FROM U.S. GEOLOGICAL SURVEY EXPLANATION 0 u -a.I ST.PETE ,.;_ SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10-POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r -;;;, 15 0 15 LEE GLADES I r---I HENDRY +


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