Hydrology of Polk County, Florida By Rick M. Spechler and Sharon E. Kroening Prepared in cooperation with the Polk County Board of County Commissioners South Florida Water Management District Southwest Florida Water Management District St. Johns River Water Management District Scientific Investigations Report 2006-5320 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2007 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Spechler, R.M., and Kroening, S.E., 2007, Hydrology of Polk County, Florida: U.S. Geological Survey Scientific Investigations Report 2006-5320, 114 p. iii Contents Abstract ...........................................................................................................................................................1 Introduction ....................................................................................................................................................2 Purpose and Scope ..............................................................................................................................2 Previous Investigations........................................................................................................................3 Acknowledgments ................................................................................................................................3 Site-Numbering System .......................................................................................................................3 Description of Study Area ............................................................................................................................4 Population, Industry, and Land Use ...................................................................................................5 Physiography .........................................................................................................................................6 Climate ....................................................................................................................................................8 Ground-Water Use ..............................................................................................................................10 Chapter 1—Ground-Water Resources of Polk County ................................................................13 Data Collection .............................................................................................................................................13 Geologic Framework ...................................................................................................................................13 Stratigraphy .........................................................................................................................................13 Karst Features .....................................................................................................................................18 Ground-Water Resources ..........................................................................................................................18 Surficial Aquifer System ....................................................................................................................19 Intermediate Confining Unit and Intermediate Aquifer System ..................................................26 Floridan Aquifer System.....................................................................................................................33 Upper Floridan Aquifer ..............................................................................................................33 Middle Semiconfining Unit and Middle Confining Unit .......................................................35 Lower Floridan Aquifer .............................................................................................................37 Sub-Floridan Confining Unit .....................................................................................................38 Ground-Water Flow System .....................................................................................................38 Recharge and Discharge .................................................................................................38 Potentiometric Surface ....................................................................................................38 Long-Term Trends in Ground-Water Levels ....................................................................................42 Head Relations ....................................................................................................................................46 Water Budget ......................................................................................................................................50 Ground-Water Quality .................................................................................................................................51 Surficial Aquifer System ....................................................................................................................52 Intermediate Aquifer System ............................................................................................................57 Floridan Aquifer System.....................................................................................................................58 Vertical Distribution of Chloride and Sulfate Concentrations ............................................62 Chapter 2—Streamflow and Lake-Level Characteristics in Polk County ............................67 Purpose and Scope .....................................................................................................................................67 Methods.........................................................................................................................................................67 Streamflow and Lake-Level Characteristics ...........................................................................................67 Streamflow Characteristics ..............................................................................................................68 Peace River Basin .....................................................................................................................70 Kissimmee River Basin .............................................................................................................74 Alafia, Hillsborough, Ocklawaha, and Withlacoochee River Basins ................................77 iv Low-Flow and Flood-Frequency Statistics .....................................................................................77 Lake Characteristics...........................................................................................................................77 Regulation of Lake Levels .........................................................................................................81 Temporal Trends in Lake Levels ..............................................................................................84 Factors Controlling Lake Levels ..............................................................................................85 Summary........................................................................................................................................................88 Selected References ...................................................................................................................................91 Appendix 1. Well and spring data-collection sites .........................................................................99-105 Appendix 2. Chemical and physical data for water from the surficial aquifer system, intermediate aquifer system, and the Upper Floridan aquifer wells in Polk and parts of adjacent Highlands, Hillsborough, Lake, Orange, and Osceola Counties ....107-112 Appendix 3. Lake and stream data-collection sites .....................................................................113-114 Figures 1. Map showing location of study area in central Florida..........................................................4 2. Graph showing historical population for Polk County ............................................................5 3-4. Maps showing generalized: 3. Land use in Polk County, 1995 ..........................................................................................6 4. Physiography of Polk County ............................................................................................7 5-6. Graphs showing: 5. Annual rainfall at Lakeland, Mountain Lake, and Avon Park, Florida, 1931-2003 ..............................................................................................................................9 6. Monthly evapotranspiration at the Disney Wilderness Preserve in eastern Polk County, August 2000 to December 2005 ...............................................................10 7. Diagram showing total ground-water use, by