On the hydrogeology of the Southwest Florida Water Management District - August 25th, 1975

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On the hydrogeology of the Southwest Florida Water Management District - August 25th, 1975

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On the hydrogeology of the Southwest Florida Water Management District - August 25th, 1975
Parker, Garald G. (Garald Gordon)
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Aquifers -- Hydrogeology -- 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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891343127 ( OCLC )
G16-00684 ( USFLDC DOI )
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• • I • • On the Hydrogeology of the Southwest Florida Water Management District 1/ Garald G. parker, C. P. G. Abstract 7'5-25 Underlying all of Florida and extending northward under the Coastal Plairi _ of Aiabama, Georgia and South Carolina is one of the world's largest and most pro lifically-yielding ground-water reservoirs, . the Floridan Aquifer. Composed chiefly of limestone and, toward its base, increasing quantities of dolostone, the .. Floridan Aquifer is the source of about 90 percent of all the water withdrawn for use in the Southwest Florida Water Management District. The District comprises all or parts of 15 counties in central western Florida and covers an area of about 10,400 square miles, an area about the size of Maryland. The aquifer is supplied by recharge from precipitation having a long-term average over the District of about 55 inches. However, evapotranspiration takes a big cut out of this, amounting to about 40 inches. The remaind~r shows up as discharge amounting to about 14 inch _ es of measured runoff from the strearns and one inch of ground-water dis charge directly into salt water of the Gulf of Mexico. Ranging in thickness up to about 3,000 feet, the aquifer's upper 2,000 feet within Flori~a contains more fresh water in storage than the entire Great Lakes system. Surrounded by salt waters of the Gulf of Mexico on the west and -by the Atlantic Ocean on the . south and east, the aquifer is underlain everywhere at some depth by salt water, some of it being brines several times as salty as the ocean. Haphazard, unplanned, and all too commonly unwise development, use and ahtise of the aquifer's supplies have created serious water problems in many areas, both of water quality and water quantity. All of the problems can be sa~isfactorily handled, given adequate funding and enlightened water management of the kind which h~s been pioneefed by the Southwest Florida Water Management District, beginning in 1969. But only a start has been made. Much additional work remains to be done ;ln large part dependent' upon the development of a better understanding of the hydrogeologY, of the Fluridan Aquifer, its natural recharge and discharge ch,1r=1cteristic s, and its re . lationships with overlying and underlying hydrogcologic u~its, its geologic facies changes, its geochemistry, a~d finally of man's impacts on its hydrologic health and well being . 1/ Certified Professionnl Geoloc:1ist, . No. Geologist and Hydrologist, McFarland Road, Tampa, _ Florida 336 1~ 69 L Consul ting and Assoc~, 3303


• • • On the Hydrogeology of the Southwest Florida Water Management District by 1/ Garald G. Parker, C.P.G.Introduction Hydrogeology is that branch of the science of geology that treats of the geologic fabric and framework in which ground water occurs and the broad geologic environment which controls the recharge, storage, transmission and qischarge of water into and out of the earth's crust. Hydrology is that branch of science that relates to water. According to Meinzer, (1942, p. 1), its central concept is the hydrologic cycle (Fig~ 1), a term to denote the circulation of water from the sea, through the atmos phere, to the land; and thence, with numerous delays, back to the sea by overland and subterranean routes, and in part, by the way of the atmosphere; also the many short circuits of the water that is returned to the atmos phere without reaching the sea . Basically, then, hydrogeology is a highly specialized division of hydrology relating particularly to ground water. 'However, especially in peninsular Florida, the surface water on the land and the salt water of the seas are commonly, closely and intimately related to ground water. The latter is the water that occurs below the water table, in the water saturated rocks of the earth's crust. Here in Florida sinkholes may swallow the entire flow of a stream --a common occurrence in such stream basins as the Santa Fe and Suwannee -and in doir.g so surface water becomes instant ground water. On the other hand, springs discharge ground water to become instant surface water. Because of this com.~on interchange of ground and surfa . ce water, the hydro geologist must become capable in evaluating the ground-water -surface water relationships. He knows that ground water and surface water are but two sides of the same hydrologic coin and in making water-resources studies the oneness of llcertified Professional Geologist, No. 691. Formerly Chief Hydrologist and Senior Scientist, Southwest Florida Water Management District; since June, 1975, Consultin~ Geologist and Hydrologist, P. E. Lat1oreaux and Associates, 3303 McFarland Road, Tampa, Florida 33618 2 Figure l near here


• • • the water resource must be recognized and prope _ rly accounted for in • water-resource evaluations. Thus, it is that in practically any modern ground-water or hydrogeologic publication there is a thorough treatment of the hydrologic cycle for the area reported upon~ Further, since the late 1950's and ~ith greater prominence ~n the 60's and 70's, water-budget studies have become the core of areal quantitative hydrologic analysis~ But our . principal objective in the current report is • to emphasize the hydrog~alogy of the Southwest Florida Water Management District (Fig.2). The District comprises some 10,400 square miles, including all or parts of 15 counties in central-western Florida centering around the Tampa Bay area. The District is about the same size as Maryland and larger than Connecticut, Rhode Island, Delaware, New Hampshire, New Jersey, Massachusetts or Vermont. Formed in 1961 as a result of the disastrous floods of March 1959 and again in March and September of 1960, the District called itself a water management district; but it wasn't until 1969 that it actually became one, and it wasn't until 1970 that the control and regulation of ground-water develop ment, use and conservation came into existence under the author's direction. At that time of undertaking control and management of Figure 2 near here the District's water resources, little specific and detailed information existed on the hydrogeology of the area, particularly of the hydrologic characteristics of the Floridan Aquifer and its relationships with the overlying and underlying units. Even to this day large areas of th~ District still lack comprehensive hydrogeologic data-gathering programs and reports upon which to base sound water-management decisions. However, the situation is rapidly being rectified, and the Southwest Florida Wate-r Management District now has a large and comprehensive cooperative program of studies of the geology and hydrology with . the u. S. Geological Survey. Additionally, the District's staff of about 35 water resources specialists, i ncluding~ core of competent young hydrogeologists, is conti nually and at an accelerating pace developing additional data and the means of storing and retrieving data for subsequent study. Likewise, the drilling of all wells 2-inches in diameter or larger requires not only a registered driller's permit but a well-completion report. With an average of about 1,000 wells a month having been drilled since January 1, 1970, ~he District now has a tremendous store of detailed knowledge available --or becoming available --to help make the detailed knowledge of the geology and hydrology far more nearly complete . 3


• • • But this isn't to say that little or nothing . of the hydrogeology was known. The cooperative investigations between the Florida Geological Survey and its succes~ors began in the early 1930's. In those early days V. T. Stringfield and David Thompson of the Survey's Ground Water Branch began the first hydrogeologic studies, working out of Washingon, D. C. headquarters. Since that early beginning, the cooperative water-resources studies have grown until now the U. S. Geological Survey's Florida District boasts the Nation's largest cooperative study program. A long list of publications has come out of thes s--studies, published mostly in the Florida Bureau of Geology ~llet,vis,~~ Information Circulars, Special Publications, . Leaflets an , 'R~~:t:i ,-in the early days (1908-1933) The Annual Reports which wer ' succeeded (1933-1960) by the Biennial Reports. Also, work by other agencies, notably the Corps of . Engineers in their investigations of the several starts and stops on the Cross Florida Barge Canal . and their extensive drainage works in the KLOE Area (Kissimmee-Lake Okeechobee Everglades) and the u. s. Soil Conservation Service with their big program of soils and drainage works in the Everglades in the 1940's, all contributed to the general knowledge of the State's hydrogeology. But back of the statewide program was the basic support and guidance of the Florida Geological Survey and its suc s~ s~rs. Always cramped for operating funds, equipment and /4 l1m1ted personnel, Ors. E. H. Sellards, Herman Gunter and Robert O. Vernon kept a notable research and investigations program going. Among other things, developing an outstanding library of well cuttings and driller's well logs on all the deep wells that could be used to determine and describe the paleontology, stratigraphy, petrology, . structure and . hydrogeology of Florida. The excellent series of publications mentioned earlier is largely the outcome of these studies. Additionally, the drilling of oil-and-gas exploratory wells supplied the Florida Survey with an invaluable mass of data regarding the deeper geologic formations. With first the discovery of the Sunniland Field, followed by other Figure 3 discoveries such as the Felda Field aria e recently the near here huge Jay Field, large new quantities of subsu~face data became available and have helped to enable the development of a reasonable good definition of fhe structure and strati~ graphy of the State (Fig. 3). With Bob Vernon's move from the Survey to the Interior Resources Division, Charles W. . "Bud" Hendry, Jr. became the new chief of the Bureau of Geology. Bud is carrying on in the tradition of his illustrious pre decessors and we should have every expectation of the success ful continuance of the drive to develop an adequate and compre hensive understanding of the geology and hydrology of the state . 4


• • • • The Hydrogeologic Framework Basic to . an understanding of the ground-water resources of any region is an understanding of the geologic fabric and framework in which water occurs. The geologic structure, stratigraphy, lithology, and chemistry of the rocks and their included fluids control the storage and transmissive capacities of the rocks under given hydraulic heads or pressures. Numerous workers, too many to list in an overview report of this kind, have contributed to our current knowledge of the hydrogeology of Florida. Their work covers the full range of geologic studies including paleontology, paleogeo graphy, stratigraphy, structure, mineralogy, geomorphology, geochemistry, geophysics, hydrogeology, hydrology, geologic history and mining geology ~ Much of the work; however, is either highly generalized over a very broad area or is in great detail on a small area. Relative to Southwest Florida Water Management District's ar~a of 10,400 square miles, there is considerable information of the generalized type and some excellent reports of the detailed type, but there currently exists a great need for a comprehensive and detailed study of the whole District, such as is presented in the U.S. Geological Survey's Water Supply Paper 1255 for southeaste~n Florida (Parker, Garald G., et al, 1955). Among the most useful over-all reports available to help defir1e the hydrogeology of the District are the following publications: Applin and Applin, 1944; Cherry, stewart and Mann, 1970; Cooke, 1945; Kaufman, 1967; Kleinj 197t; _ Matson and Sanford, 1913; Parker, Ferguson and Love, 1955; Pride, Meyer and Cherry, 1966; Puri and Vernon, 1964; Shampine, 1965a, b, c, and d; Stewart, Mills, Knochenmus and Faulkner, 1971; Stringfield, 1933a, 1936, and 1964; U.S. Geological Survey 1973, 1974a and b; Vernon, 1970; White, 1970; and Wilson, 1975. Among the most useful limited area reports, the ~ allowing are outstanding: Coble, 1973; Knochenmus, 1971; Menke, Meredith and Wetterhall, 1961; Peek, 1953; Robertson, 1973; Shattles, 1965; Sinclair, 1~75; Stewart, J. W. and Manan, 1970; Stewart, J. W. and Hughes, 1974; Stewart, H. G., 1966; Stringfield, 1933b and 1933c; Vernon, 1951; and Wetterhall, 1964 . 5


• • • The Stratigraphic and Structural Setting The Peninsul~r Arch and the Ancient RocksPuri and Vernon (19~4) collaborated to prepare the most comprehensive and succinct report available depicting the subsurface geology of Florida. I couldn't do better in developing this topic for the present paper • than to utilize two of their illustrations, with minor modifications: their Figure 1, "Generalized Geologic Cross Section . s Through Florida" (my figure 3) and "Panel Diagram of Post-Avon Park rocks in Central Florida." Plate 5 (my figure 4) • Based chiefly ~pon petroleum and gas exploratory data, the structural and stratigraphic interpretation depicted in Fig. 3 was developed. Test-well cuttings and corings, with supplementary geophysical data, defined the huge Peninsular Arch. This is an immense anticlinal dome of folded, faulted and metamorphosed sediments, pyroclastics and ign~6s rocks, including basalts and gabbros. In general, these rocks appear to be the southern, deeply-buried extension of similar rocks in the great Appalachain Mountains Chain. Its flanks descend from the crest of the Peninsular Arch in Levy County at an altitude of about 3,200 below mean sea level to depths greater than -16,000 feet msl. Draped over these chiefly dense, crystalline rocks ranging in age from Pre-Cambrian to Triassic, are Mesozoic 1Jura~sic and Cretaceous) sediments that thicken outwardly in all directions from the crest of the Peninsular Arch. Composed mainly of dense limestone, dolostone and evaporites (a~hydrite, gypsum, halite and other similar rocks) these beds contain no fresh ground water at any depth. They do, instead, contain salt brines, some of which are many times saltier than the sea. The Sunniland and Felda Oil Fields, of the Big Cypress Swamp area, and the Jay Field of the extreme northwestern Florida Panhandle, produce large quantities of these brines. Where not carefully handled and prevented from escaping to the land surface or e underlying fresh-water aquifers, . these brines could constitute a serious threat to the adjacent fresh-water resources. In the early ~ays of the development of oil in Florida (the late 1940's), careless waste of these brines occurred in the Sunniland Field but the problem and danger therefrom is now under control. The brines, after separation from the petroleum, are returned in deep disposal wells to the depths of their origin. This means, for Sunniland Field, about -12,000 feet msl and for the Jay area about -16,000 rnsl . 6 Figure 3 near here


• • • Except for the oil-related brines, the pollution problem and the structural geologic conditions that caused a great deepening of overlying Cenozoic sediments outward from the crest of the Peninsular Arch, hydrogeologists have little concern for these de~ply buried, a~cierit, up-bowed rocks . . The Ocala Uplift and the Cenozoic RocksOverlying the uppermost Mesozoic rocks, the Upper Cretaceous sediments with their included salt water and salt brines, are the Cenozoic formations in whicp our usuable fresh-water aquifers have been formed. These rocks arid their combinations that form aquifers or confining beds (aquic~udes) are the chief concern of the hydrogeologists and the main topic of this report. A glance at Figure 3 and the map inset shows the Cenozoic materials to range in depth from about 1,600 feet msl atop the crest . of the Peninsular Arch to more than 6,000 feet ~sl in the Sunniland Field area to about 4,500 feet below rnsl at the western terminus of the Florida Panhandle, near Jay Field . The Ocala Uplift, a later and much smaller uplift than the Peninsular Arch, raises Eocene limestone and dolo stone up to altitudes of 80 feet above msl in an irregular, . elliptical, patchy area about 45 miles long in a N26w direction and about 20 miles wide. This domal crest extends from-the vicinity of Dunnellon to Ellzey, mostly in Levy . County. The mapping is shown in great detail, together with the associated fracture patterns created by the folding and faulting of the Ocala Uplift, in Vernon's (1951) report, especially Plates 1 and 2 and Figure 11. Aquifers and AquicludesThe gross structural and stratigrao . ~ lations of . the ro6ks of prime concern to the hydroqeologists working in centrai Flotida are shown . in the fenc~ diagr~ws, Figure 4. Basically, the geologic structure, iiratigraphy and lithology . combine to create two primary hydrogeologic units. The . uppermost unit consists primarily of a widespread, g e nerally sandy mantle of quartz sands w i th som e intercalated silt a nd clay lens e s, extending f rom t h e land sur f ace downward t o depths averaging about 30 . to 40 feet but in places as d e ep as 600 f ee t wh e r e the sands fill deep, dilated faults 7 Fi q ur e 4 n e ar h c r r.


• • • or large and deep sinkholes. These sediments range in age from Holocene through the Pleistocene in the northern part of Central Flor i da and through the Pliocene (Caloosahatchee Formation) in the southern part of the state. Their relation ship to the underlying, older formations is shown in the fence diagrams, Fig. 4. Together these uppermost sediments constitute the Shallow, or Water-table Aquifer. Commonly beneath the Shallow Aquifer there is a more~or-less continuous confining bed of lowly permeable clay, clayey marl, or other dense, silty and clayey materials, and in the Central Florida Phosphate District the phosphate ore layer, commonly called "the matrix," lies immediately beneath the Shallow Aquifer (Fig. 5). Generally the Ha~thqrn Formation acts as a confining layer between . the Shallow Aquifer and the underlying Floridan Aquifer. However, over large areas the basal Hawthorn con tains a permeable--even cavernous--limestone section that is hydraulically connected with the underlying Floridan Aquifer. In these areas the Hawthorn limestones are considered to be part of the Florid~n Aquifer, "Florida's rainbarrel," from which about 90 percent of all the water developed for human use in peninsular Florida is taken either from flowing or pumped artesian wells . Figure 5 near here By means of arrows placed alongside the ends of the fence diagrams in Figure 4, the thickness and disposition of the Shallow Aquifer, Confining Beds and Floridan Aquifer are shown. Figures 5 and 6 f~rther depict these relationships, with the network of caverns and connecting horizontal and vertical solutional passageways emphasized. Fig. 5 also emphasizes the fact that in the southwestern part of SWFWMD the Ocala Group of limestones (Crystal River, Williston and Inglis Limestones) are of low permeability and non-cavernous. In other parts of the state, notable in the outcrop area of these limestones from the Green Swamp northward, eastward and westward , these formations of the Ocala Group are not only highly permeable but are also quite caverno~s and both store and transrni t trem . endous quanti t:i . P.c:; n-f wate r ~ Figure 6 shows the existence of a Secondary Artesian Aquif e r in th ~ Hawthorn Formaticin lying between . confining beds above and b e low. This secondary aquifer is widely spread over --,----southern and southwestern Florida, commencing on the southern Fi g ur e l > shoulders of th e Gr e en Swamp High (Fig. 7) and extending southn ea r h e r w a rd along th e Gul f Coas t to and b e yond Everglades City, wh e re it serv e s a s th e princ i pal artesian aqui f er. The Floridan in the Everglad e s City area is deeply buried and cont a ins salty, sulfurous water unfit for culinary purposes. F1~ur ~ 1 r. r -: u -h er , _ 8


• • • The Floridan Aquifer Scientific studies of the geology and artesian waters of Florida were first begun on a systematic basis by F. G. Clapp and George C. Matson of the U. S. Geological Survey in 1907, working first in northern and central Florida and finally statewide. At about the same time; Dr. E. H. Sellards and Herman Gunter, Assistant Geologist and in 1913 Sellard's successor as State Geologist, began work in the central Florida ar ea. Matson' s and Sanford's work was . published in 1913 as U.S. Geological Survey Water-Supply Paper 319, but contained no maps of the artesian pressure surface. The work of Sellards and Gunter appeared in reports by Sellards (1908); Sellards and Gunter (1910), (1911), and (1913). None of these reports contained maps of the a~tesian pressure surface. During these early days the Floridan limestones in which the art~sian wells were developed were called "Vicks burgian" and included the rocks now called the Suwannee Limestone, Ocala Group and Avon Park Limestone. It seems possible that these early workers thought of these "Vicksburgian" rocks as a single hydrologic unit, _ but they did not describe them as such. N~ither did their work lead to the mapping of an artesian water-level surface ~ which later was called a npiezometric surface" and more lately has been and is now being called a "potentiometric surface". Later, when Stringfield began his work in Florida under David Thompson's direction in 1930, he may have recog nized, but did not describe, the hydrologic unit which we now call the Floridan Aquifer. In his early reports Stringfield _ (193.3a, 1933b, 1933c and 1936) simply refers to . the "principal arte . sian formations" as the Ocala Limestone, the Tampa Limestone and the Hawthorn Formation, but he apparently treats them as a unit. In his report on "Artesian Water in the Florida Peninsula" (1936, plates 10 and i2) he maps respe.ctively the "Area of Artesian Flow" in 1934 and "The Piezometric Surface of Artesian Water" in 1934. This potentiometric map was the first const r ue ed for Florida and indicates, again, that Stringfield th ~ ~; 1 of the source of the artesian water as being from a single, large, hydrogeologic unit --an artesian aquifer-~ but he did not call it that nor did he give it a name at this time. It wasn't until the 1940's, app~rently, . that Stringfield began to think of this huge artesian system, which he recognized as extending into Alabuma, Georgia and South Carolina, as the "principal artesian aquifer". To my knowledge, the first published reference to "The Principal Artesian Aquifer'' in Florida occur~ simultan e ously i n reports by Par k er and Ho y (19 4 4) and Unkle s b ay {1944) . Maps of the "piezom e tric" sur :fa c t ) ( a s it w as th e n c all e d) occur in both reports. 9


• • The early workers, as noted earlier \ c~lled the rocks in which artesian wells were developed "V1.cksburgian". Later these rocks were found to be of Eocene, Oligocene and Miocene ages, and in these times the Eocene rocks were all called "Ocala Limestone" (Cooke, 1945). Later these rocks were found to be of distinctly different ages and were divided into three separate formations; from oldest to youngest these were named the Inglis, Williston and Crystal River Limestones (Puri and Vernon, 1964). With each change of stratigraphic nomenclature there came a need to re-name the sources of the artesian water, first from Vicksburgian to Ocala and later to Inglis, Williston or Crystal River. Applin and Applin (1944) discovered that the lower parts of the "Ocala" also should be separated out, and they named and described the Avon Park Limestone and the Lake City Limestone. But through all the stratigraphic name changing it became apparent that, over most of the state, these separate formations (no matter what the stratigraphers called ~hem) were in essence one huge, folded and faulted hydrologic unit with more or less _ effective hydraulic interconnection between the formations. For these reasons, and similar problems he had with stratigraphic nomenclature interfering with understanding of the hydrology of southern Florida, the writer erected three new hydrogeologic units: (1) The Floridan Aquifer; (2) the Biscayne Aquifer; and (3) the Floridan Aquiclude (Parker et al, 1955). The latter unit was established to simplify the terminology for the principal artesian confining bed, which consists mainly of a thick mass of clays and silty _ marls of the Hawthorn Foundation but also, in places includes clays, marls and other dense detritals of the Tampa, Choctawhatchee, Caloosahatchee, Alachua and Tamiami formations. South of Lake Okeechobee the Floridan Aquiclude ranges in thickness from about 400 to 600 feet . . Because of facies changes in the geologic formations that compose theie three units, large differences in trans_ missivity, storage and leakage occur from place to place. In large parts of Florida, particularly the area from the lati tude of Tampa Bay and the Green Swamp High northward, the Floridan Aquifer is fairly homogenous in its vertical tran~miisibility and water moves rather easily f op to base of the aquifer or vice versa. On the other hand, in the area south of the latitude of the Green Swamp Hig~ facies changes take place that have important consequences in ground-water development, management and conservation. In the area of the crest of the Green Swamp, only th 2 Shallow Water-table Aquifer overlies the Floridan Aquifer. In some areas, particularly in the western part of th e Green Swamp, the commonly present clay layer b e tw e en the~ Water-table and Flor i dan Aqu i fers is eith e r lacking or thin • a nd ineffective as a con f ini n g la y er. Howev e r, to th e south l . O


• • • and southwest first one, then two . and finally up to five aquifer zones have been identified (Sproul and Others, 1972; Sutcliff e , 1973). Somewhere between Polk City in the Green Swamp and Punta Gorda on Charlotte Barbo~ the simple Shallow Aquifer -Floridan Aquifer system becomes completely split into the . di verse high-and low-permeability zones described by Sproul and Others in the Fort Myers area and by Sutcliffe in the Punta Gorda area. These relationships are in great need of being carefully sorted out and mapped, but to do this will require a considerable amount of expensive test-well drilling, core and cuttings studies, geophysical borehole exploration, geochemical testing of the various zones and finally the construction of hydrogeologic maps, cross sections and the construction of potentiometric-surface maps for each water-bearing (aquifer) zone. Some notable advances have been made in tracing out and defining these zones which, below the Hawthorn , I recognize as Floridan Aquifer Zones but not as separate aquifers. The work of Herbert Stewart in Polk County (1966), of Al Robertson in the Lakeland Ridge (1973), of Bill Wilson in Hardee and De Soto Counties (1975 open file?), of Sutcliffe in Charlotte County (1973) and of Sproul, Boggess and Woodard in Lee County (1972) has helped greatly to attain the understanding we now have . of the aquifers, aquifer zones and confining beds (aquicludes) of this southern part of the SWFWMD, but a great deal more must be learned to fill in the chinks in our understanding. The ~urrent move of the phosphate industry into Hardee, De Soto, southeastern Hillsborough and eastern Manatee County will do much to provide the missing knowledge. Information that the phosphate companies and oil companies, with their teams of consul ting geologist and hydrologists, are required to present in their A.D.A. (Application for Development Approval) and D.R.I. (Development of Regional Impact) State ments to gain mining and water-use . permits, will help immensely in supplying detailed hydrogeologic information that could have been obtained in no other way. Already a half-dozen or more such ADA and D~I reports are either completed or in the process of completion. Wilson (personal communication, 1975) recognizes in Hardee and De . Soto Counties, abo~t ~idway between Polk City and Fort Myers, three subdivisions in the Surficial Aquifer: (1) An upper sand unit averaging about 25 feet thick; (2) a shelly sand unit averaging abo u t 28 feet thick; and (3) a phosphorite unit averaging about 14 feet thick. Average trans missivity of this unit is , about 1,300 ft2/day or, in values of .. • . ..


• • • the old coe~ficient of transmissibility, T = 9, . 725 gpd/ft. Shallow producing wells average about 65 feet deep in De Soto County and up-dip, in Hardee County, about 40 feet. Most . are "open hole'' (i.e., unscreened) in their lower parts and yield a few tens of gallons per minute. Regarding the highly productive Floridan Aquifer in De soto and Hardee Counties, Wilson's data show that it consists there mainly of limestone and dolostone. He divides the aquifer into upper and lower units which are separated by the sand-and clay unit of the Tampa Limestone (Figuie 6). Note also that a distinct lithologic facies change takes place in the southern area and thus in the ~ater-bearing qualities of this unit. The upper unit is composed of permeable parts of the Hawthorn and Tampa Formations. It is about 160 feet thick and down-dip in De Soto County reaches thicknesses up to 200 feet. In a pumping test near Arcadia, Wilson reports T = 22,440 gpd/ft. Wilson's lower unit of the Floridan Aquifer is composed of limestone and dolostone of the Suwannee Limestone, the Ocala Group and the Avon Park Limestone. The unit averages more than 900 . feet in thickness. To gain the greatest yields, most wells a.re completed in the upper part of the Avon Park. Wilson calls this the "Dolostone Unit", a cavernous and highly permeable zone of rock. Wells finished in it are high yielders, though large differences are reported between different parts of the two cqunties. He reports (Wilson, 1972) values of T = 2,020,000 gpd/ft; S = 0.00015 ft/day/ft and leakance (Krb' 0.00015 gpd/ ft2 ). This contrasts with data from another pumping test at a well in the southwest part of De Soto County where T = 81,500 gpd/ft; other hydrologic parameters . were not derived. _ Regarding natural hydraulic head in the Floridan Aquifer, Wilson (personal communication) has measured, in the Peace River Valley and the southern part of De Soto Couqty, typical increases in head ~ith depth. He reports that elsewhere in De Soto and Hardee Counties the hydraulic head generally de creases with depth _ in the Floridan Aquifer. This phenonenon (decreasing head wi ' -n ,~ . th} is not common elsewhere in the . District and at present is not satis~actorily explained. It may be due~ however~ to large-scale downward leakage into zones of • high~r T values where large-scale pumpage from de~p wells in the Dolostone Unit of the Avon Park Limestone hai low~red pressures over a large area and induced downward leakage from overlying, less permeable zon e s. The USGS water-use study of De Soto and Hardee Counties in 1970 indic a t e s that an av e rage of 94 mqd of qround water is p ump e d from tl w aq ui fe rs ( hief l.y from th e }\van Park Lim e stone, f or use in D e S o t o an d H~rdce Co u n t i e s. By w a y of h e lping 1.2


• • • visualize how much water 94 mgd is, it is roughly the amount of water currently used by Tampa and St. Petersburg combined. Of this, 96 percent is for irrigation and a large, but un measured part, is wasted as tail-water runoff to Peace River and thence to salt water of Charlotte Barbot. Such large abstractions of water from the Dolostone Unit could quite likely produce the decrease of head in depth that Wilson has noted. A comparison of potentiometric maps of SWFWMD, one each for 1949, 1964, 1969, 1971, 1973 and 1974, helps explain and develop an understanding of the situation. The earlier maps by Stringfield (1933; 1936) are essentially the same as that of 1949 (Fig. 8), therefore these earlier maps are not shown. They indicate no large and significant withdrawals from the aquifer up to and including 1949. Principal changes in these early days of Florida's development relate to changes in natural recharge and discharge from the aquifer. Such normal changes in potentiometric levels seldom exceed more than 10 feet at inland sites and usually are less than a foot or two near the Gulf of Mexico shoreline. But beginning in 1964 (Fig. 9) with largely increasing phosphate and citrus industrial use of water in the upper Peace and Alafia River Basins in Polk County, a large lowering of water levels began and resulted in development of a wide plateau-like area between the 70-and 80-foot contours on the potentiometric surface (Fig. 9). By 1969 (Fig. 10) a 50-foot closed contour had developed in this Polk County area of large drawdown and for the first time ever, ground-water flow from the main recharge areas of the Green Swamp High were cut off from furthe~ westward flow into Hillsborough and Manatee Counties to the west. From this date on, this huge sink has persisted and generally has grown larger and deeper with the passing of time and the growth and expansion of phosphate and citrus industrial use of water in this area. By 1971 (Fig. 11) the Polk County cone-of-depression had grown still larger and deeper. At this i its central area stood at 40 feet above sea level, register i tg 40 to 50 feet of loss of head in this area since 1949. But on this ~ap a new feature shows up for the first time-~ a wide and deep salient that pushed the 40, 30, 20, 10 ~nd 5-foot contours inland many miles along a NW-SE corridor extending Figure 8 near here Figure 9 near here Figure 10 near here Figu+e 11 ~6ar her ~ from SW Hillsborough County into SE Hardee. This could only have been caused by the very large increases in agricultural irrigation in southern Hillsborough, much of central dnd eastern Manatee and much of western Hardee and De Soto Counties. As 1 3


• • • • related earlier, the USGS water-use survey for 1970 showed 94 mgd being pumped out of the Floridan Aquifer in this area, mostly for irrigation from the Avon Park Limestone. There is no other large withdrawal of water to blame for this large, new potentiometric lowering inasmuch as 4 percent of the pumped water was used for purposes other than irrigation. In 1973 (Fig. 12) there was improvement in the drawdown in the ar~a. The Polk County cone-of-depression recovered 10 to 18 feet and showed a 50-foot above sea level contour in the Figure 12 central area of drawdown (Fig. 12). Even the area of the near here salient extending into De Soto County from the northwest showed improvement. But 1974 (Fig. 13) showed a resumption of the falling water levels. In the Polk County area~ where 1973's lowest water level stood at \ 50 feet above sea level, a new record was set with levels reduced to 20 feet above sea level, a fall of more than 60 feet compared with 1949 levels. In the salient extending southeastward to southeastern De Soto County, an extensive widening occurred bending the 30-foot contour in a big reentrant in De Soto County from about 7 miles wide in 1973 to about 28 miles wide; and water levels in this re entrant area had declined 45 to 50 feet below levels of 1949. By 1974 the long-term decline of artesian water levels in Polk, Hardee, De Soto, Manatee and southern Hillsborough had reached startling porportions. Clearly, aquifer storage was being depleted much faster than nature could recharge the system. And even though seasonal changes of level may show recoveriss of water level at the end of the irrigation season amounting to as much as 30 feet, the over-all, long-term trend of water levels is down. It will take a great deal of wise and careful water-use management, including the reduction of all possible wastes, to prevent disastrous, long-lasting drawdowns that could cause upconing of poor quality water into . the existing fresh-water supplies. In the Tampa Bay area the hydrogeology is much simpler than in the Peace and Alafia River Basins. Here there is a fairly simple hydrologic system consisting of a shallow, Water table Aquifer separated by a clay or fine-sand confining bed from a well-integrated, layer-cake arrangement or limestone dolostone beds of the Floridan Aquifer. The Shallow Aquifer transmits recharge from rainfall into the underlying Florid~n Aquifer either through the leaky confining beds, or directly to the Tampa Limestone where the confining beds are absent. Large amounts of recharge take place through deep, sand-filled sin k holes, or, . as in some places east of Tampa, through open 1 4 Figure 13 near here


,_ . sinkhole chi~neys more than 200 feet deep and up to 100 feet ormore in diameter. In this region and extending north to and beyond the District's northern boundaries, there is a minimum of layering in the Floridan Aquifer and excellent hydraulic communication generally exists from the uppermost limestones of the Floridan Aquifer to its base in salty water. Cavernous systems are present in all the formations from those in the Tampa Limestone downward. Greater permeability commonly exists in the Suwa~nee and Avon Park Limestones than in the Ocala Group in this region. This greater permeability is' commonly related to large, inte grated underground cavern systems, some of which probably are many miles long. Northward in Oitrus and Levy Counties and eastward into the lower Withlacoochee River Basin and on into the lower Oklawaha River Basin, the rocks of the Ocala Group form . most of the upper part of the Floridan Aquifer. In this northern part of the District these rocks of the Crystal River, Williston and Inglis, together with the overlying Suwannee wherever it is present, are highly permeable and cavernous and readily accept recharge by seepage from the overlying Water-table Aquifer. It is principally in these hydrogeologic units that so many of Florida's large first-and second-order springs occur. • These huge springs, including Weeki Wachee, Chassa-• howitzka, Homosassa, Crystal River, Rainbow and Silver are the land-surface terminals of many miles of inter-related underground drainage systems consisting of interconnected caverns and tubular channels draining hundreds of square miles. The Silver Springs Basin, for example, ~s paramecium shaped. It is about 6 0 miles long in a general north-south direction, about 15 miles wide at its greatest width, near Ocala, and covers about 600 square . miles. The flow of Silver Springs averages about 530 mgd, all of which originates by . rainfall on the land surface of the Silver Springs Ground water Basin. Another larg ng, Rainbow, drains a huge area of . nearly 880 squar~ miles adjoining the Silver Springs Basin on the west. Rainbow, with an average daily discharge of about 520 mgd, is f e d by an extensive~ branched underground system of feeder channels. No surface stream worthy of the name flows on the land surface of the Rainbow Springs Basin. The rainfall tha ~ penetrat e s the sandy mantle sinks quickly into the underlying Flor i dan Aquif e r and reapp e ars in Rainbow Spring's orific e or as flow from dispersed smaller springs and seeps in Blue Run. Blu e Run is the 6-mi~c long river 1 5


• • • that connects Rainbow Spring with the Withlacoochee River and thus feeds it~ 14.5 inches of annual runoff into Lake Rofisseau, a short distance west of Dunnellon. At . this point, some 140 miles away from its source in the Green Swa~p, the Withla coochee's average flow is about 752 mgd, or 8.65 inches ~er yea~. Thus the underground drainage system of Rainbow Spring is a far more efficient producer of runoff (14.5 in/yr) than is the Withlacoochee's surface-water system (8.65 in/yr). Oddly enough, when the eleven drainage basini of the SWFWMD were being drawn up in 1961, those drawing the basin boundaries included only the small area of Rainbow Springs and Biue Run in the Withlacoochee Basin (Parker and Hernandez, 1975). The rest of the Rainbow Springs drainage basin went unrecognized and wa$ included in the 550 square-mile Waccasassa River Basin to the west -~ a totally unrelated hydrologtc feature . . Inasmuch as the 1972 Water Resources Act provides for transferring the Waccasassa Basin from the SWFWMD to the newly established Suwannee River Basin, this act needs modification. In actuality, the true Waccasassa Basin of 550 square miles is hydrologically unrelated to the Suwannee Basin and, since the statutorially constituted Waccasassa Basin includes Rainbow Springs 880 square miles of drainage with the Waccasassa, the act in essence cuts off 8 80 square miles of Withlacoochee drainage. Working this enigma out to satisfy the facts of hydrogeology and the needs of good water management seems to be a difficult task for State government. As of this writing, no final act has b~en made to correct the original error and leave the Rainbow Springs Basin where it belongs --in the Withlacoochee Basin . 16


• • • Selected Bibliography Applin, P. L. and Applin, E. R., 1944, Regional subsurface stratigraphy and structure of Florida and Southern Georgia: Am. Assoc. Petrol. Geol. Bull. v. 28, no. 12, p. 1673-l753 Cherry, _ R. N., Stewart, J. W. and Mann, J. A., 1970, General hydrology of the Middle Gulf area, Florida: Fla. Geol. Survey Rep't of Inv. no. 56, 96p. Coble, R. W., 1973, The Anclote and Pithlachascptee Rivers as water-supply sources: Fla. Bur. of Geol. Map Series no. 61 Cooke, C. w., 1945, Geology of Florida: Fla. Geol. Survey Bull. 29, 339p. Kaufman, M. I., 1967, Hydrologic effects of ground-water pumping in the Peace and Alafia River Basins, Florida: Fla. Div. of Geel. Rep't of Inv. no. 49, 32p. Klein, H., 1971, Depth to base of potable water in the Floridan Aquifer: FlaBur. of Ge~l. Map Series no. 42 Knochenmus, D. D., 1971, Ground water in Lake County, Florida: Fla. Bur. Geol. Map Series no. 44. Matson, G. C. and Sanford, s., 1913, Geology and ground waters of Florida: u. s. Geological Survey Water Supply Paper 319, 445p., Washington, D.C. Meinzer, O. E., 1942, Hydrology: Physics of the earth IX, McGraw Hill Book Co., Inc . , i'L Y., H. Y., 71 __ ): -,. genke, C. C., Meredith, E.W. and Wetterhall, W. S., 1961, Water resources of Hillsborough County, Florida: Fla. Geel . Survey Rep't of Inv. no. 2~ !Olp. Parker, Garald G. and Hoy, N. D., 1944, Geology and ground water of the Kissimmee River -Lake Okeechobee area, Florida . : Soil Sci. Soc. of . Fl a . Proc . . , v. 6, p. 20-70. Parker, Garald G., Ferguson, G. E., Love, S. K. and others, 1955, Water resources o f south e astern Florida with special reference to the g e ology and ground water of the Miami area: U. S. G e ological Survey Water Supply Paper 1255, 965p . , Washington ~ D.C. Parker, Garald G. and H e rna nde z, P .A., 1 9 75, Where are pioper boundaries of th e Withlacooch e e River: Southwest Fla. Wat~r Mgm't District, . The Hydroscope, v . 6, no. 2, p. 2 3.


• Peek, H. M., 1958, Ground-water resources of Manatee County, Florida: Fla. Geol. Survey Rep't of Inv. no. 18, 99p. Pride, R. W., Meyer, F. W. and Cherry, R. N., 1966, Hydrology of Green Swamp area in central Florida: Fla. Geol. Survey Rep't of Inv. no. 42, 137p. Puri, H. S. and Vernon, R. O., 1964, Summary of the geology of Florida and a guidebook to the classic exposures: Fla. _ Geol. Survey Spec. Pub. no. 5, 312p. Robertson, A. F., 1973 Hydrologic conditions in the Lakeland Ridge area of Polk County, Florida: Fla. Bur. of Geol. Rep't of Inv. no. 64, 54p. Sellards~ E. H., 1908, A preliminary r~port on the under ground water supply of central Florida: Fla. Geel. S _ urvey Bull. 1. Sellards, E. H. and Gunter, H., 1910, The Artesian water supply of eastern Florida: Fla. Geel. Survey 3rd Ann. Rep't., p. 77-200 Sellards, E. H. and Gunter, H., 1911, The water supply of west Florida: Fla. Geol. Survey 4th Ann. Rep ' t. ,p. 87-154 . Sellards, E. H. and Gunter, H., 1913, The artesian water supply of eastern and southern Florida: Fla. Geel. Survey 5th Ann. Rep't., p. 103-290. Shampine, W. J., 1965a, Chloride concentration in w~ter from the upper part of the Floridan Aquifer in Florida: Fla. Geol. Survey M ap Series no. 12. Shampine, W. J., 1965b, Hardness from the upper part of the Floridan Aquifer in Florida: Fla. Div. of Geol. Map Series no. 13. Shampine, W. J., 1965c, Dissolved solids in water from the upper part o ~ th~ Floridan Aquifer in Florida: Fla. Div~ of Geol. Survey map Series no. 14. Shampine, W. J., 1965d, Sulfate concentration in water from the upper part of the Floridan Aquifer in Florida: Fla. Div. of Geol. Map Series no. 15. Shattles, D. E., 1965, Quality of water from the Floridan Aquifer in Hi 11 s bo r ou , 1 h County , Florid a , 1 9 6 3 : Fl a • Div. of G e o 1. Map S eri.es no. 9.


• • • Sinclair, W. c., 1975, Hydrogeclogic characteristics of the Surficial Aquifer in northwest Hillsborough ~aunty, Florida: Fla. Bur. Geol. Info. Circ. no. 86. Sproul, C. R., Boggess, o~ H. and Woodar~, H.J., 1972, Saline-water intrusion from deep artesian sources in the Mc Gregor Isles area of Lee County, Florida: Fla. Bur. Geel. Info. Cir. no. 75, 35p. Stewart, H~ G., Jr., 1966, Ground-water resources . of Polk County, Flor~da: Fla. Geol. Survey Rep't of Inv. no 44, 170p. Stewart, J. W. and Hanson, R. V., 1970, Hydrologic factors affecting the utilization of land for sanitary landfill in northern Hillsborough County Florida: .Fla. Bur. of Geol. Ma~ Seri~s no ; 39. 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, U.S. Geol. Survey ijydrol. Atlas H.A.-440. Stewart; J. W. and Hughes, G. H., 1974, Hydrologic con sequences of using ground water to maintain lake levels affected by water wells near Tampa, Florida: Fla. Bur. of Geol. Rep't of Inv. no. 74, p.41. Stringfield, V. T., 1933a, Ground-water investigations in Florida: Fla. Geol. Survey Bull. no. 11, 33p. Stringfield, V. T., 1933b, Ground-water resources of Sarasota County, Florida: Fla. Geol. Survey 23rd24th ~nn. Rep't for 1930-1932, p. 121-194 . . Stringfield, V. T., 1933c, Exploration of ~rtesian wells in Sarasota County, Fla., Geol. Survey 23rd-24th Ann. Rep't for 1930-1932, p. 195-234. Stringfield, V. T., 1936, Arte~ian water in the Florida Peninsula: U. S. Geological _ Survey Water-Supply Paper 773-C, p. 115-195~ Stringfield, V. T., 1966, Artesian water in Tertiary limestone in the southeastern states: U. S. Geoloiical Survey Prof. Paper 517, 226p., Washington, D.C .


• • • Sutcliffe, H. Jr., 1973, Appraisal of the water resources of Charlotte County, Florida: U. S. Geol. Survey Open File Report no. 73010, 6lp. Unklesbay, A.G., 1944, Ground-water conditions in Orlando and vicinity, Florida: Fla. Geol. Survey Rep't of Inv. no. 5, 7 Sp. U.S. Geological Survey, 1973, Water resourc~s data for Florida, Pt. 2, Water quality records: Tallahassee, Water Resources Division, 614p. U.S. Geological Survey, 1974a, Water resources data for Florida, Pt. 1, Surface water records, vol~ 3, Lakes: Water Resources Division, Tallahassee, 208p. U. S. Geological Survey, 1974b, Water resources data for Florida, Pt. 1, Surface water: Tallahassee, Water Resources Division, 339p. Vernon, R. O., 1951, Geology of Citrus and Levy Counties, Florida: Fla. Geol. Survey Bull. no. 33, 256p. Vernon, R. O., 1970, The beneficial uses of zones of high transmissivities in the Florida subsurface for water storage and waste disposal: Fla. aur. of Geol . Info. Circ. no. 70, 39p. Wetterhall, W. S., 1964, Geohydrologic reconnaissance of Pasc6 and southern Hernando Counties, Florida: Fla, Geol. Survey Rep't of Inv. no. 34, 28p . . White, W. A., 1970, Geomorphology of the Florida Peninsula: Fla. Geol. Survey Bull. no. 51, 164p. Wilson, W. E., 1972, Hydrogeology of Florida's largest citrus grove: ASCE Conference on age of changing priorities for land and water, Irrig. and Drainage Dtv., Spok a ne, Wash., p. 293-308 Wilson, W. E., 1975, Ground-water resources of De Soto and Hardee Counties, Florida: U. S. Geel. Survey Open ~ile Rcp't, Tallahas~ee; Fla., 244 ms. p. t-Ut> . 7 5 .. 2Cf



• • • -----S.W.F.W.M.D . Fig. 2 Index map showing the location of the Southwest Florida Water Management District


..... (Jq ; . ------------------------------------~ ~ ------Generalized Geologic Cross Secfions through Florida A 11 ... --------------------816miles-----------------------,i} ~: ___..ay . Fleld ........-Levy County -Sunnlland Field ! i MSL ................ ___ -,--_________________ _._ _____________ __. _______ 4-i~1~1~hee--~ Suwannee Straits CENOZOIC -----2 South Florida --Embeyment CENOZOIC COMMONWEALTH WELL STRUCTURE 1!_L-.------------------------------------------SCALE IN MILES ADAPTED FROM PURI & VERNON CH , UPLI I / Kl // ~t~xu I /FLORIDA PENINSULA SEDIMENTA PROVINCE I I D.N.R., e.o.G. SPECIAL PUBLICATION NO. 5, 1964 30 0 30 IO to OUTHEAST GEORGIA EMBAYMENT SOUTH FLORIDA EMBAYMENT




• • • ---------------. 0 500 1000 1500 2000 Idealized Hydrogeologic Cross Section, Western Hardee & De Soto Counties SECONDARY AQUIFER & CONFINING LAYER HAWTHORN FORMATION BASAL LIMESTONE HEST ZONES PERMEABILITY E CO M MONLY AT CLOSE TO RMATION CONTACTS CAVERN SYSTEM (NOT TO SCALE) a: w u. 5 0 ct :z ct 0 0 .J u. Fig. 5 Idealized Hydrogeologic Cross Sectio11, Western Hardee and DeSoto Counties


• • • Poten iometric su face of Floridan Aqui er for May ,1 974 ADAPTED FROM U.S. G EOLOGICAL SURVEY EXPLANATION SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDAR Y 10--POTENTIOMETRIC SURF ACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DI \/ID SCALE IN MILES r -----. 15 0 11 HIGHLANDS _ . __ J GLADES I --r---• LEE HENDRY Fig. 7 Potentiometric Surface of Floridan Aquifer for May, 1974 showing the Green Swamp, Putnam Hall and Pasco Highs and the Peninsular Florida Hydrologic Divide


1-:rj ..... (J'q . m . g1 ::r:: . . '. 11 11 '< , H, s:i, p.. ; p) c-1'-11 C 1-1, 0 : ..ro ; "O 0 j ~ O"' 0 . p) .... . (J'q '< C ..... , ..,:C::: C : C.O tj 0 . -:i ..... 11 , c.n fi!" 0 rn p) rn tj Ul o. ro C 11 C. 0 0 tj ,..... c-1'-ro O"' 0 11 ...., 0 c-1'-J:: g'. 0 ::s 11 c-l'..... 11 p.. p) p) ,..... tj ::r:: > p) .0 11 J:: p.. ..... ro ro 11 0 ~o 0 M-tj ro q tj C. rn 0 O"' s ro ..... ::s ..... (J'q C • • ---Hydrogeologic Cross Sectfon through Central Hard e e County showing Stratigraphic Units and Profile of the Floridan Aquifer Potentlometric Surface, May 1975 .. N N .1 a, ('I) en N co N..1 ~w I 3: ~us ~d -s-~--N.E.-r.:,, POTENT,OMETRIC SURFAC OF HAWTHORN AQUIFER MSL ;;t,~!!f!f!t , .,:~ :: ~: , ~~::~ , : .. __ . T• ~ -~ -: : : ~ ~~~~~:: _ ~-::: .d ~ : :~~:~r-: _ .. _,: ::: •: .. •: : , ~: , , : ; ,_;. ~ . -. "" J . .. .. "{\tm@t~}i .... . ~ ;i ti~ : ;j1~~; . ,, • •:,, . , A . ';:~~~;~~ : t ' ~ s -. '1:,;w ,r LIMEST ::~~~g~ ~ --:;:ili&:1;::'f,;,; • 600 1'. i: ,: -/it-',:: E l s-'"~~4~ ~.,,. v .,:;_.•>,""' 'F5'"'' 800 5 z C a OC A LA G R OU P 10001;: ; :;: l !ti~i ! ~ l .......,....... @ ~ U:JM~ . fr.~~ : ! : : : : ii: :j i iJ : ! : u; i ! [; i ILiliU t@Ji : iiLd DO L O ST ONE U NI T OF AVON PARK LIMESTONE 1200} : : : : Z-i ! ' • "" •r, :a;,~,,,", " , . .,-,, ' '-•• " - • , ,..... , . • ,-'-'~'"""' " •, "''"'' $• • ._, .. ' ... ,,_, .. ., , "' • ,,. ; •-• ,, ~ • . • ... ,,.;-;:' •-•+••r•0 ••-' --,-:3 asi c Infor :: !ati o n ; u . s . Ge o l o ci ca l Surv ey , '.i'ai : 1 :pa , :'lor::..da • Scale Ratio, Vertical to Horizontal :s 1: 5280 Scale In Ml les i---i 1 0 1 2 3


• • • Potentiometric Surface of Floridan Aquifer for Sept.,194 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 EXPLANATION -SOUTHWEST FLORIDA WATER O _ MANAGEMENT DISTRICT BOUNDARY 10_.... POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r--. 15 0 15 GLAD~S I r---I HENDRY Fig. 8 J?otentiometric Surface of Floridan Aquifer for September, 1949 and the Peninsular Florida Hydrologic Divide


• • • Potentiometric Surface of Floridan Aquifer for Jan., 1964 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 EXPLANATION (Y'_ -SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10-POTENTIOMETRIC SURFACE CONTOUR -PENINSULAR FLORIDA . HYDROLOGIC DIVIDE SCALE IN MILES r ~-1 15 0 15 I pSCEOLA \J \ \..... --,--_ I LEE I HENDRY Fig~ _ 9 Potentiometric Surface of Floridan Aquifer for January, 1964 and the I>eninsular Florida Hydrologic Di~ide


• • • Potentiometric Surface of Florid a n Aquifer for May, 1969 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 EXPLANATION 0 u -YI""_ SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10-POTENTIOMETRIC . SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r --1 15 0 15 LEE I OSCEOLA \J \ \..... GLADES --r--. I HENDRY Fig. . 10 Potentiometric Surface of Floridan Aquifer for May, 1969 and the Peninsular Florida Hydrologic Diyide


• • • • ' :t \_~ I "\ TAY LOR L~FA Y Ell~ ~-~, ST . JOHNS . T . ILCHRIST' '\J,:=, / ' "-. I Potentiorrietric Surface of Floridan Aquifer for May. 1971 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 0 u EXPLANATION . YI"'_ SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10_.... POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r --1 15 0 15 / j PUTNA\ ~• _ __y ALACHU I 50 30 -~ILLE L.,,-,~~ >O \ ~LAGLER LEE \l__ I yo~ -\ ' DO GLADES --r---• HENDRY F~g. 11 Potentiometric Surface of Floridan Aquifer for May, 1971 and the Peninsular Florida Hydrologic Divide


.. • • • ' \_,./ I "\ YLOR L~FAYETTE ~---------.. , ST. JOHNS • HRIST' '}-..... I PUT~ ~-_y" Potentiometric Surface of Floridan Aquifer for May, 1973 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 EXPLANATION v,;:_ SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10_.... . POTENTIOMETRIC SURFACE CONTOUR --PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE IN MILES r -s;., 15 0 15 LEE \LAGLER L_ IA t • GLADES --t---1 HENDRY _ Fig. 12Potentiometric Surface of Floridan Aquifer for May, 1973 and the Peninsular Florida Hydrolog~c Divide


• • Potentiometric Surface of Floridan Aquifer for M ay,1974 ADAPTED FROM U.S. GEOLOGICAL SURVEY 3-29-75 EXPLANATION SOUTHWEST FLORIDA WATER O MANAGEMENT DISTRICT BOUNDARY 10_.POTENTIOMETRIC URF'. . E CONTOUR -PENINSULAR FLORIDA HYDROLOGIC DIVIDE SCALE . IN MILES r ~-1 15 o _ 15 I HIGH LANDS GLADES __ t_ __ I LEE !HENDRY Fig. 13 Potentiometric Surface of Floridan Aquifer for May, 1974 and the J?eninsular Florida Hydrologic Divide


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