HYDROLOGY OF THE FLORAL CITY POOL OF TSAIA APOPKA LAKE, WEST-CENTRAL FLORIDA By L.A. Bradner U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 88-4024 Prepared in cooperation with the SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT Tallahassee, Florida 1988 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director For additional information Copies of this report may be write to: purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Books and Open-File Reports Section Suite 3015 Federal Center, Building 810 227 North Bronough Street Box 25425 Tallahassee, Florida 32301 Denver, Colorado 80225 CONTENTS Page Abstract.............................................................. 1 Introduction.......................................................... 2 Historical background............................................ 2 Purpose and scope................................................ 5 Previous studies................................................. 5 Acknowledgments.................................................. 6 Geography and geology................................................. 6 Hydrogeology.......................................................... 6 Water use............................................................. 6 Physical properties of the Floral City Pool........................... 7 Hydrologic conditions................................................. 9 Rainfall and evaporation......................................... 9 Surface water.................................................... 9 Water-level fluctuations.................................... 9 Floral City Pool........................................ 9 Streams................................................. 11 Streamflow.................................................. 11 Ground water..................................................... 15 Upper Floridan aquifer...................................... 15 Surficial aquifer system.................................... 20 Hydrologic relations among the Withlacoochee River, the Floral City Pool, and the Upper Floridan aquifer................................ 20 Withlacoochee River.............................................. 20 Floral City Pool................................................. 22 Upper Floridan aquifer........................................... 24 Surface-water movement near the Floral City Pool...................... 24 Orange State Canal............................................... 24 Leslie-Heifner Canal............................................. 27 Golf Course Canal................................................ 28 Site 1........................................................... 28 Site 2. .......................................................... 28 Site 3. .......................................................... 29 Site 4........................................................... 29 Site 5. .......................................................... 29 Site 6........................................................... 30 Site 7........................................................... 30 Lake Bradley Canal............................................... 30 Little Lake Canal................................................ 30 Ferris Canal..................................................... 30 Moccasin Slough.................................................. 31 Streamflow patterns................................................... 31 High-range water levels .......................................... 32 Middle-range water levels ........................................ 34 Low-range water levels ........................................... 36 1985--A year of extremes .............................................. 36 Water quality......................................................... 38 Floral City Pool................................................. 38 Canals and river................................................. 39 Ground water..................................................... 39 Hydrologic considerations for water management........................ 39 Inflow to the lake system........................................ 40 Withlacoochee River......................................... 40 Canals...................................................... 40 CONTENTS- -Continued Page Hydrologic considerations for water management--Continued Outflow from the lake system..................................... 41 Canals...................................................... 41 Summary............................................................... 41 Selected references................................................... 44 PLATE Plate l.--Map showing water-management system and data-collection In sites near the Floral City Pool........................... pocket ILLUSTRATIONS Page Figures 1-3. Maps showing: 1. Location of study area............................ 3 2. Water-management system and data-collection sites near the Floral City Pool................. 4 3. Depth contours of Floral City Lake, December 1985................................... 8 4-7. Hydrographs showing: 4. Water levels of the Withlacoochee River near Floral City and the Floral City Pool, 1957-86......................................... 10 5. Water levels of the Withlacoochee River near Floral City, the Leslie-Heifner Canal, the Orange State Canal, and the Floral City Pool, July 1984 through June 1986..................... 12 6. Streamflow in the Withlacoochee River near Floral City, July 1984 through June 1986........ 13 7. Streamflow in Orange State and Leslie-Heifner Canals, with comparison to water levels of the Orange State Canal and the Withlacoochee River near Floral City............ 14 8-9. Maps showing: 8. Potentiometric surface of the Upper Floridan aquifer in the Tsala Apopka Lake area, May 1985............................. 16 9. Potentiometric surface of the Upper Floridan aquifer in the Tsala Apopka Lake area, September 1985.................................. 17 10-12. Hydrographs showing: 10. Water levels of the Floral City well, 1977-86...... 18 11. Water levels of the Withlacoochee River near Floral City, the Floral City Pool of Tsala Apopka Lake, the Duval Island well, and the Floral City well, July 1984 through June 1986.... 19 12. Comparison of high-, middle-, and low-range stages of the Withlacoochee River before and after construction of the Wysong Dam at Carlson....................................... 21 iv ILLUSTRATIONS- - Continued Page Figure 13. Graph showing stage-duration curves of the Withlacoochee River near Floral City and the Floral City Pool, 1957-85.............................. 23 14. Diagram showing gradient of the potentiometric surface of the Upper Floridan aquifer across the Floral City Pool....................................... 25 15-17. Maps showing: 15. Streamflow during high-range water levels (above 41.0 feet elevation) of the Floral City Pool, September 25 through October 1, 1985.............. 33 16. Streamflow during middle-range water levels (39 to 41 feet elevation) 'of the Floral City Pool, June 4, 1986 ................................ 35 17. Streamflow during low-range water levels (below 39 feet elevation) of the Floral City Pool, March 25, 1985 .................................... 37 TABLE Page Table 1. Streamflow data for selected water-level periods at data-collection sites in the Floral City Pool area, Tsala Apopka Lake, 1985-86......................... 32 v HYDROLOGY OF THE FLORAL CITY POOL OF TSALA APOPKA LAKE, WEST-CENTRAL FLORIDA By L.A. Bradner ABSTRACT The chain of lakes known as Tsala Apopka Lake in west-central Florida has a surface area of approximately 19,000 acres. It is divided into three water- management pools: the Floral City Pool, the Inverness Pool, and the Hernando Pool, in downgradient order. The Floral City Pool has an extensive combina­ tion of lakes, wetlands, and connecting canals. Surface area of the pool is approximately 4,750 acres during years of average rainfall. The main influence on changes in lake levels in the Floral City Pool is inflow from the Withlacoochee River through the Orange State and Leslie- Heifner Canals. Inflow is controlled through structures in the canals oper­ ated by the Southwest Florida Water Management District. Water flows from south to north through the Floral City Pool and exits through the Golf Course Canal control structure and the uncontrolled Moccasin Slough area. Desired water-level fluctuation in the Floral City Pool is 2.0 feet, from 40.25 to 42.25 feet elevation, but lake levels stay below 40.25 feet elevation approximately 40 percent of the time. The Withlacoochee River, which supplies inflow to the lake, remains below 40.31 feet approximately 40 percent of the time. Virtually all inflow ceases when the river level drops below an eleva­ tion of 38.0 feet. Less-than-normal rainfall occurred in 1984 and early 1985, resulting in reduced inflow to the Floral City Pool. During the time of little or no surface-water inflow in May and June 1985, the lake level dropped approx­ imately 0.04 foot per day and surface area of the lake reduced to approx­ imately 700 acres. Heavy rainfall in August and September 1985 brought lake levels back to desired management levels. Surface-water inflow exceeded evapo transpiration and outflow between June 10 and September 27, 1985. At the same time, the lake surface area increased from 700 acres to 4,750 acres. By the end of September 1985, the surface-water outflow was 338 cubic feet per second and the surface-water