Ground-water accretions to streamflow in Horse and
 Pony Creek basins _.. --- -....----__ .._ ....... ..------------------. ---.. 61
 Aquifers ---........ -- -----------_. .--------- ...........----------- ..----. 64
 Nonartesian aquifer .-__ ........--------------------- -- 69
 Description of the aquifer ..--.. .. .-...........---- ---- -----------. --.... ---. 69
 Recharge and discharge ....-------...-.-------------------. 69
 Hydraulics of the nonartesian aquifer ------.. ........-.------------. 76
 Chemical characteristics of nonartesian ground water ------- 78
 Secondary artesian aquifer .....------.-....- ------------.. -- 78
 Relation to Green Swamp area ..........-----.--------------- 78
 Floridan aquifer ....-............... ----------- ------ 79
 Description of the aquifer ----...---------------------------- 79
 Recharge and discharge .---------------------------- 79
 Hydraulics of the Floridan aquifer ................----.--------------. 82
 Chemical quality of water in the Floridan aquifer ..----....--...---- 87
 Hydrochemistry of the Floridan aquifer in central Florida .---. 89
Analysis of the hydrologic system .. .--.-..------ -------.---.- --------. 92
 Rainfall, runoff, and water loss --...-..---- ----.. -. -----------------------.. 92
 Water-budget studies .......----------------------.--.--------- 99
 Evaporation and water budget of Lake Helene ...---....--...-.-----------.. 101
 Comparison of eastern and western basins ...-... .... .--------- ----.. 105
 Outflow from Green Swamp area ....................------------- .---. 109
Evaluation of proposed plan of water control __...----.--.--- ------ ----. 119
 Reduction of flood peaks in the Hillsborough River ....--.....-...---------... 119
 Reduction of flood peaks in the Withlacoochee River ...........---------.. 122
 Effect of water impoundment in Green Swamp Reservoir on
 ground-water levels ....------...---.- ------------------------------- 125
 Effect of water impoundment in Southeastern Conservation
 Area on ground-water levels ...... ..... ..--------------------- 126
Significance of the hydrology of the area .--....------ -- ..--------- 127
References -. -----------------------------------..---. 131
Glossary ------- -.------------------- --------- ----- 134



 ILLUSTRATIONS

Figure Page
 1 Ma.p of Florida showing location of Green Swamp area ------ -- 3
 1 Map showing data-collection points in Green Swamp area .. In pocket
 3 Diagram showing the well-numbering system used in Florida ..----. 6
 4 Map showing topography of central Florida and its relation to
 Green Swamp area -- ------ -------- In pocket
 5 Map showing surface-water drainage features of Green Swamp
 area ___-- --- In pocket
 6 Graphs showing annual and mean monthly rainfall of Green
 Swamp area ----- _.. 25
 7 Relation of annual water loss to temperature in humid areas _..- 26
 8 Generalized geologic cross sections along lines A-A', B-B' and
 C-C' _--- ----- ---- --- In pocket
 9 Map showing contours on top of the Avon Park Limestone __ In pocket
 10 Flow-duration curves for Withlacoochee River basin, 1931-62 -..----. 37