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CHARLOTTE COUNTY v. SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
B. Geography, Hydrology and Water Use in the District 1. District Groundwater Basins and Aquifer Systems 130. Varying hydrogeology throughout the District influences groundwater location and accessibility. Along the coast, where a significant portion of the District's population is clustered, groundwater supplies are limited and primarily brackish. Differences in hydrogeological characteristics also influence the consequences of withdrawing fresh water from underground aquifers. Thus, a withdrawal in the northwestern part of the District will have significantly different impacts than the same size withdrawal in the southwestern part of the District. 131. The Floridan Aquifer provides 90 percent of Florida's drinking water and underlies most of the state and a large portion of the Southeastern United States. The Floridan Aquifer is composed of porous rock (including limestone) that is laterally extensive throughout Florida and parts of Georgia, Alabama, and South Carolina. A hydrological interconnection can exist throughout a region of the Floridan Aquifer system where there is a continuous distribution of porous rock with no geological barriers to lateral groundwater flow. 132. The location and depth of the Floridan Aquifer below ground varies greatly within the District. It is close to the land surface in the northern part of the District, but it lies 600 feet or more below the land surface and is overlain by a clay confining layer in the southern area. In some areas, particularly in the southern part of the District, the surficial and/or intermediate aquifers are found between the land's surface and the Floridan Aquifer. 133. Where the Floridan Aquifer is close to the surface (e.g., in Pinellas, Pasco and Hillsborough Counties), a withdrawal reduction in groundwater from the aquifer can directly affect surface waters and wetlands. From southern Hillsborough County through Manatee County, the Floridan Aquifer runs far beneath the surface, and the intermediate aquifer, encased in rock and clay, forms above it. 134. Rainwater that is absorbed into the ground can serve to replenish or recharge an aquifer. Variations in geology affect an aquifer's recharge capability and rate as well as the potential for contamination or adverse impacts to natural systems as a result of groundwater withdrawals. There are areas in the District where recharge is poor because the aquifer is either very deep or the overlying soil is composed of clay or some other non-porous substance.31 In such areas, water withdrawn from a confined aquifer can be replaced by horizontal flow within the aquifer. 135. A groundwater basin is generally defined as an area within which all of the groundwater is derived from rainfall and recharge from that area. As a general rule, rainfall and recharge that occur on one side of a groundwater basin divide tend to travel in one direction, while rainfall and recharge on the other side of the divide migrate in a different direction. 136. A withdrawal from one location within a groundwater basin can affect water resources throughout the entire basin. 137. While the measurable change that a withdrawal has at any particular location within a basin depends on the proximity of the withdrawal site to that location, withdrawals from within a groundwater basin affect the overall condition and/or potential of the water resource. 138. There have been some variations and resulting confusion in the identification and nomenclature of groundwater basins in the District. In most depictions of groundwater basins prior to 1987, the District's jurisdictional area was divided into the Northern West-Central Florida Groundwater Basin ("NWCFGWB") and the Southern West-Central Florida Groundwater Basin ("SWCFGWB"). The boundary between the basins was a groundwater divide that generally ran in a westerly direction from the potentiometric "high" in the Green Swamp (located in northern Polk County), through another high in Pasco County, to a point on the west coast that lies within northwestern Pasco County. This delineation is consistent with and apparently based upon the United States Geological Service (USGS) Regional Aquifer Systems Analysis ("RASA") depictions of the Floridan Aquifer system. This configuration has been utilized by the District in many reports over the years and has been reflected in some District illustrations as late as 1993. 139. As part of its investigation of water resource problems in certain areas, in particular the eastern Tampa Bay region, the District has identified an additional groundwater divide based on persistent groundwater flow lines in the Upper Floridan Aquifer System. This divide extends in a southwesterly direction from the Green Swamp potentiometric high to Tampa Bay and essentially splits the SWCFGWB into the "Central Basin" - lying north of the persistent flow line and encompassing much of the area now designated by the District as the Northern Tampa Bay Water Use Caution Area ("NTB WUCA")32 - and - the "Southern Basin" lying south of the divide and roughly coinciding with the area currently designated by the District as the Southern Water Use Caution Area ("SWUCA").33 140. The District's recognition and delineation of two distinct groundwater basins within the SWCFGWB is not without precedent. Similar basin boundaries have been used by researchers as early as 1980. 141. Several parties have objected to the District's delineation of the Southern Basin as a distinct hydrogeologic groundwater basin, noting that the USGS does not depict or officially designate the area as a separate basin on its potentiometric surface maps. However, the USGS focuses on major regional basins and views the Floridan Aquifer only from a macro perspective. The failure of the USGS maps to specifically depict the Southern Basin does not obviate the results of the District's analysis of groundwater flow lines. Persuasive evidence was adduced at the hearing to support the District's analysis and its delineation of the Southern Basin. 142. In sum, the District currently identifies three groundwater basins within its jurisdictional area: the Northern, Central and Southern Groundwater Basins.34 Each basin represents a hydrologically distinct groundwater flow system of the Upper Floridan Aquifer, with limited groundwater flow across basin boundaries. The groundwater divides are not absolute barriers to flow. Changes in potentiometric surface levels can affect the location of a basin divide and, absent a specific geologic barrier, the boundaries of a groundwater basin can fluctuate or shift with changing conditions. Theoretically, a withdrawal of water from the Central Basin could impact potentiometric levels within the Southern Basin. However, to have a noticeable impact, the withdrawal would have to be fairly significant and located close to the basin divide. 143. The Central Basin is less confined than the Southern Basin and is generally described as "semi-confined." In other words, the groundwater aquifers are often directly connected to the water table and to surface water bodies. Consequently, withdrawals of groundwater in this area tend to impact wetlands and other surface water features more immediately and noticeably than withdrawals in the Southern Basin where the Floridan aquifer is more confined. While there is some interconnection between the Floridan Aquifer and the intermediate and/or surficial aquifer in certain areas of the Southern Basin, the District's studies indicate that the linkage is isolated and sporadic. 144. With regard to the quantity and availability of groundwater within its jurisdiction, the District completed initial "Groundwater Basin Resource Availability Inventory" reports on all but two of the counties within its region by 1988. The investigations undertaken in connection with this inventory helped the District to identify certain problem areas as discussed in Section III-C below. The District continues to assess and update the report data.35 145. Within the District's boundaries, there are thirteen major rivers (five of which provide public water supply) and approximately 1,800 lakes measuring at least 10 acres. The productive groundwater system in the District consists primarily of the following three aquifers in descending order: the surficial, intermediate, and Upper Floridan. The depth of the aquifers varies greatly throughout the District. In some areas, particularly in the northern and eastern parts of the District, there is no intermediate aquifer. Different zones or pockets of relatively consistent geology have been identified for the intermediate and Floridan Aquifers in various areas of the District. 146. The surficial aquifer extends downward from the land surface to the top of the upper confining bed of the underlying aquifer system. The surficial aquifer provides a base flow of water to rivers, lakes and streams and acts as a repository for water that is required for evapotranspiration and recharge to the underlying artesian aquifers. Discharge from the surficial aquifer occurs by seepage into lakes and streams, evapotranspiration, downward leakage into the underlying aquifers, and pumping. 147. Lakes and wetlands are part of the surficial aquifer system, which is an important source of recharge to the Floridan Aquifer. In areas where the aquifers are not well-confined, groundwater withdrawals from the Floridan Aquifer can induce the leakage of water from the surficial aquifer into the Floridan Aquifer, thereby lowering lake levels and/or reducing surface water flow. 148. The intermediate aquifer system consists of all water bearing units and confining beds between the overlying surficial aquifers and underlying Floridan aquifer systems. Basically non-existent in Pasco County and sporadic along the Highlands Ridge, the intermediate aquifer system is used in varying degrees as a source of water in the Southern Basin. The formation begins about 15-20 miles south of the Pasco-Hillsborough County line, and the thickness of the water-bearing portion increases to about 300 feet at Charlotte County's southern boundary.36 149. The Upper Floridan Aquifer System ("UFAS") is the most highly developed and productive limestone reservoir in west- central Florida, and is currently the lowest-cost source of high quality fresh water in southwest Florida, supplying water for public consumption, agriculture and industry for much of the District, except in Charlotte County37 and the coastal area of Sarasota County. 150. The UFAS consists primarily of porous limestone and dolomite units. As noted above, the degree of confinement of the UFAS changes between the Central and Southern Basins. The UFAS in the Central Basin is less confined with much greater connection between the UFAS and other aquifers and surface water features. The increasing confinement in the south is due to the thickening of the confining bed, the occurrence of the intermediate aquifer and the presence of a confining unit separating the intermediate from the UFAS. 151. Generally, the base of the UFAS is the top of the middle confining unit of the Floridan Aquifer, which is sometimes called the evaporites. This relatively impermeable confining layer separates the overlying fresh water portion of the UFAS from the lower Floridan Aquifer which underlies much of the UFAS. The lower Floridan Aquifer is comprised of highly saline brine and is not a source of groundwater supply. 152. While technologies exist for treating a wide range of low-quality water to drinking water standards, treatment becomes increasingly expensive as water quality falls. Water quality in the UFAS is generally very good above the evaporites, but it deteriorates at the base of the UFAS and toward the coast. 153. As groundwater moves down-gradient in the UFAS, limestone, dolostone and gypsum units are dissolved. Groundwater near the bottom confining layer of the Upper Floridan has a high concentration of sulfates and total dissolved solids (TDS). 154. In the coastal areas, chloride-rich seawater is located beneath the sulfate-rich groundwater, and water quality decreases with depth from the fresh, bicarbonate-rich groundwater above, through sulfate-rich saline water, to chloride-rich water of seawater origins. In other words, the saline water consists of a layer of mineralized water characterized by sulfate concentrations that are much higher than chloride concentrations. Seawater, which possesses chloride concentrations up to seven times greater than sulfate concentrations, exists below the mineralized water in the coastal areas. In the inland areas, seawater is generally not present in the UFAS but there is poor quality, highly mineralized water at the base of the aquifer. 155. Chloride levels in the parts of the UFAS that have been completely flushed with fresh water are generally about 25 mg/liter. Seawater contains chloride concentrations of approximately 18,500 mg/liter and TDS levels (which include chloride, sulfate and other minerals) of approximately 35,000 mg/liter. The coastal water-quality transition zone between the fresh water and saltwater is interpreted by the District to begin at a chloride concentration of 1,000 mg/liter. Chloride concentrations above 1,000 mg/liter are non-potable and cause crop damage. 156. The saline water which underlies the fresh water in the Floridan Aquifer is connected with the Gulf of Mexico through the aquifer system and has a relatively constant head (of pressure) nearly equivalent to sea level. The interface between the fresh and saline waters is not abrupt or sharp; it occurs over distances of one to several hundred feet. In other words, a zone of transition in water quality exists between the fresh and saline waters. When the pressure in the aquifer is reduced in the coastal areas, the transition zone between fresh water and saline water shifts. This movement of the interface causes what is commonly known as saltwater intrusion. The nature of this problem in the District is explored further in Section III C-1 a. below. 157. Aquifers, such as the UFAS in west central Florida, that were filled with saline water during some geologic period(s) in the past can contain "connate water." Connate water was entrapped in sediment or the pore space of rock after its original deposition or the most recent retreat of the sea. Connate water is easily recognized by its chemical signature. Some of the parties have suggested that connate water explains much of the poor water quality currently being reported in the Southern Basin. The more persuasive evidence established that connate water is not present in significant volumes in an aquifer, such as the Southern Basin, that is interconnected and has experienced a high degree of flushing. 158. In a confined aquifer, the water in the pores of the rock is pressurized. The potentiometric level or surface at a particular point in an aquifer represents the total head in the aquifer at that point, and is made up of both the pressure head and the elevation head. The pressure head is a determination based upon the height to which a column of water would rise in a tightly confined well. The elevation head is a measure of water surface in relation to sea level. 159. A potentiometric surface map consists of contour lines charted from well measurements of an aquifer in a particular geographic area. Potentiometric surface maps do not portray the distribution of pressures in the aquifer; rather, they depict the distribution of its total head, which is a reflection of the energy available to produce the movement of water. 160. The earliest map of potentiometric surface levels in the District was prepared by Stringfield in the 1930's. In 1980, R.H. Johnston and others prepared a "predevelopment38" potentiometric surface (or "water level") map of the Upper Floridan aquifer system based upon the earlier Stringfield Map modified to reflect available information on changes that had occurred as a result of pumpage. While it is impossible to completely and accurately determine predevelopment groundwater levels, the more persuasive evidence established that the Johnston Map was based on the best available data and is a reasonable and the most reliable depiction of predevelopment conditions of the UFAS within the District. 161. The USGS has a well-developed system of monitor wells for the UFAS and utilizes data from the wells to prepare potentiometric surface maps. It has contracted with the District to prepare potentiometric surface maps for the District twice each year. One map is based upon measurements taken in May, following what typically represents the dry season and the time of heavy agricultural pumping. The second map is prepared in September, following completion of the rainy season when withdrawals from the Upper Floridan are typically low. 162. For the most part, in the areas pertinent to this proceeding, the UFAS is generally free of impediments to the lateral movement of water within the aquifer, although there are variations in District hydrogeology that influence how persistent flow patterns develop. 163. Groundwater flow in the UFAS originates as rainfall that percolates downward. "Leakance" is a measure of the ease with which water flows through a confining unit into an aquifer. "Leakage" or "recharge" - the actual flow of water through the confining unit - can occur naturally when a gradient exists, or can be induced by the pumping of groundwater beneath the confining unit. 164. In areas of high recharge, rainfall that is not lost to evapotranspiration eventually recharges the aquifer. In areas where there are subsurface confining layers reducing recharge capability, significant amounts of rainfall become run-off into streams or other surface waters. In a low-recharge area, such as eastern Tampa Bay, horizontal flow is the primary way in which water withdrawn from the aquifer is replaced. Depending on the head differentials, that flow can be saline water from the coast or fresh water from the east. 165. A drop or reduction in the potentiometric surface of an aquifer can result in differing hydraulic heads among the various aquifers. Depending upon the geology at a particular site, the aquifers will tend to equilibrate, which can result in downward leakage (induced recharge) from the overlying aquifers resulting in lower amounts of surface water run-off. Thus, a decline in the potentiometric surface can affect streamflow and/or lake levels by increasing the potential for downward leakage from the overlying aquifers. 166. The direction of groundwater flow within the UFAS is affected by changes in potentiometric levels within the aquifers. As the hydraulic gradient (i.e., the amount of fresh groundwater moving towards the coast) decreases, the saltwater transition zone moves vertically upward in the aquifer and is reflected by the inward or landward movement of the saltwater-freshwater interface. Lower potentiometric surface levels can also cause the deterioration of inland water quality due to the upward movement of chlorides and sulfates from the poor-quality mineralized water that lies at the base of the Floridan Aquifer. Water withdrawals from deep wells above the zone of mineralized water can produce an effect called "upconing," where the low-quality water is drawn up into the freshwater aquifers. When groundwater withdrawals exceed groundwater recharge, upconing can increase. 167. "Transmissivity" is a key aquifer characteristic that influences how a groundwater withdrawal-induced drawdown in the potentiometric surface is transmitted throughout a confined aquifer.39 Groundwater withdrawals at different locations can create very different cones of depression depending on transmissivity. 168. Although wide variations exist throughout the Floridan Aquifer, it is generally considered a very transmissive unit within the District with measurements in the "high" range for measured aquifers worldwide. Partly because of its high transmissivity, the Southern Basin equilibrates relatively quickly. Thus, after heavy groundwater pumping in May, lowered potentiometric levels recover significantly by September, when the amount of pumping is significantly lower and the rainy season has just concluded. 169. Upon implementation of a water use permitting program in 1975, the District began the process of converting common law uses to permitted uses. Owners of domestic wells that serve individual households were not required to obtain permits. See, Section 373.219(1), F.S. Most other users were required to obtain a WUP in order to continue the use. 170. As of the final hearing in this case, the District had issued 10,230 permits.40 Approximately 93 percent of the current outstanding permits are for quantities less than 0.5 MGD. These permits, which are characterized under the District's existing rules as "general permits,"41 account for about 22 percent of the total quantity of permitted water withdrawals District-wide. The remaining 7 percent of the permits account for 78 percent of the total quantity permitted. In fact, roughly 52 percent of the total permitted amount can be attributed to one percent of the permits. 171. Subsection 373.236(2), F.S., authorizes the issuance of a water use permit for up to fifty years for certain public supply purposes. For other uses, permits up to twenty years are authorized. See, Section 373.236(1), F.S. Because the District has been obligated to process permit applications while it was gathering data and accumulating information regarding the condition and interactions of the various resources, the District has generally issued permits for shorter periods, in part so that it retains flexibility to adjust to conditions as they become known. Under the current rules, the District generally issues a new permit for the withdrawal of 0.5 MGD or more for a period of 6 years or less. For a withdrawal of less than 0.5 MGD or for the renewal of an existing use where no problems or difficulties have been encountered during the prior term, permits for up to 10 years are typically issued. The District's rules and the Basis of Review provide sufficient flexibility to allow issuance of a permit for a longer term when the facts warrant it. 172. "Permitted quantity" refers to the maximum amount of water that a user is allowed to withdraw under a District-issued permit, assuming no emergency or other restrictive conditions at the time of withdrawal. Due to a variety of factors, permitted quantities and actual water use can be substantially different figures. Such a discrepancy is particularly common with agricultural permits.42 173. In 1989, the District began work on a "Needs and Sources Study" -- a major water supply research and planning project. The most recent draft of this study available at the hearing was dated January 1992. The District anticipates updating the study every two years. The study predicts water use trends for all major users in the District for the ensuing thirty years. According to the Needs and Sources Study, total freshwater use within the District for 1990 was estimated to be over 1625 MGD. The Study estimates that groundwater presently supplies 90 percent or more of current water supply demands in the District. 174. Some of the parties have challenged the accuracy of the data on actual water use within the District and in particular, the Southern Basin. The evidence established that the District utilized the best information available and that the information provides a reasonably accurate estimate of actual water use. Precise data on actual water use is not available because only permit-holders withdrawing large quantities of water have historically been required to monitor their use. Under the District's existing rules, all water users permitted to withdraw 0.5 MGD (500,000 gallons) of water or more must submit metered pumpage records to the District.43 Permittees who pump less than 500,000 gallons per day are not required to meter their pumpage except permit-holders who (1) irrigate pasture land or (2) are located in a Water Use Caution Areas ("WUCA"), and are permitted for at least 100,000 gallons of water per day.44 175. Prior to October 1989, agricultural operations were exempt from metering requirements.45 Metered records of actual agriculture use are now becoming available. Consequently, the accuracy of actual use estimates within the District has increased significantly in the last few years. 176. No persuasive evidence was presented to establish that the lack of totally accurate historical water use data is a basis for rejecting or disregarding any of the District's studies or analyzes. The District's estimates are the best information available. 177. Water use is sometimes classified into the following broad categories: agricultural; industrial; mining; public supply; and recreational. 178. During the period from 1975 through 1995, water use in the District increased for public supply and agriculture (primarily citrus and tomatoes), but decreased for industry (principally phosphate mining).46 Public supply has been the fastest-growing category of the District's water uses, more than doubling since the 1970's. 179. Agriculture is a major contributor to the District's economy and a large number of agricultural operations are located in the Southern Basin. The District has worked for several years with representatives of the agricultural community to determine and implement more efficient irrigation techniques. The District is proposing water conservation measures for farms in the SWUCA that will involve the increased use of efficient water-delivery systems such as "drip" irrigation, which delivers water to crops through a flexible, perforated pipe. Compared to traditional irrigation methods, drip systems can be relatively expensive to install and maintain. 180. The Needs and Sources Study forecasts that district water demands will rise to nearly 2400 MGD by the year 2020, with the largest user (agriculture) requiring about 1050 MGD, or about 44 percent of the total estimated demand based upon the efficiencies existing at the time of the study. 181. While the District projects that water conservation and greater use of reclaimed wastewater and desalinized water will reduce dependence on groundwater and surface waters in coming years, the Needs and Sources Study anticipates that groundwater will remain the primary source of fresh water. The projected increases in demand heighten concerns over the impacts of groundwater withdrawals. The District is faced with the immense and interrelated responsibilities of determining the nature and extent of the existing problems, developing adequate data and understanding of the systems and formulating long term management strategies while administering the current regulatory program. The District already characterizes the current overall condition of water resources within its jurisdiction as "stressed." As discussed below, the District has been examining particular problem areas over the past several years.
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