Lake Panasoffkee SWIM Plan - Southwest Florida Water ...

percent of the river's dry-season flow. Recorded average daily discharge from the lake to the
river has ranged from 99 cis (64 mgd) in 1992 to 288 cis (186 mgd) in 1973.
Two aquifers lie in connection with Lake Panasoffkee; the water table, or suficial aquifer
which exists in the unconsolidated sediments, and the upper part of the Floridan Aquifer found
in the deeper limestone layer. The water table is recharged by rainfall. Losses from the lake
occur mostly through outflow, evaporation, some through downward leakage into the artesian
aquifer, and minor amounts through pumpage. The Floridan Aquifer is recharged via water
table leakage, sinkholes, and small discharges from the Green Swamp. Several springs and
sinkholes are found in the vicinity of the lake and .ts tributaries that probably resulted from
solution cavities formed along limestone fractures.
Figure A 4 shows the groundwater basin boundaries for the lake as compared to the surface
water boundaries. The contributing groundwater basin area is approximately 300 square
miles and flows in a northwesterly direction from the Green Swamp to Lake Panasoflkee.
Since there is a hydraulic connection between the lake and the aquifer, water level changes
in the Floridan Aquifer will directly affect water levels in the lake.
Rainfall is the only recharge source to the lake's ground water supply so the amount and
timing of rainfall greatly impacts the ground water table. Since rainfall patterns are erratic, the
amount of rainfall on a basin can vary between points; however, in an average year, this basin
receives 55 inches of rainfall and loses 48 inches through evaporation (Heath and Conover
1981) leaving an average annual
surplus of seven inches. Total annual
rainfall for 1969 to 1999 is compared
to the period of record (POR) mean in
Figure A-5.
Water Budget
Variation from Mamn Annual Ftalnfal
for* Period from 1968 to 1899
Direct surface water inputs to Lake
Panasoffkee include Little Jones
Creek, Big Jones Creek, Shady Brook,
and small ungaged streams. The
subbasins associated with direct
inflows to Lake Panasoffkee represent
about 13,900 acres, which is 35
percent of the total contributing
drainage basin. Therefore,
approximately 65 percent ofthe 39,800
acre (62.2 mi2) watershed contributes
flow to ~ake ~knasoffkee as sheetflow or via small ungaged streams (CH2MHill1995). The
single output is the Outlet River, historically known as Spring Run. The Outlet River is a two
mile run and joins Lake Panasoffkee to the Withlacoochee River at Princess Lake.