144 REPORT OF INVESTIGATIONS No. 50
The major areas of discharge of ground water are springs in Orange and Seminole Counties, seepage into St. John River and Wekiva marsh, and underground flow into Seminole, Lake and Brevard Counties.
Yields of 4,000 gpm or more can be obtained from largediameter wells finished in the limestones almost anywhere in the county.
The water level (piezometric surface) in wells that penetrate the Floridan aquifer ranges from about 15 feet above the land surface in low lying areas of the county to more than 100 feet below the tops of some sand hills in the rolling highlands. In the Orlando area, the piezometric surface fluctuates as much as 20 to 25 feet from extreme wet to extreme dry periods partly because of the variation in recharge from numerous drainage wells. In outlying areas of the county the level fluctuates only about 5 to 10 feet.
The dissolved solids in the water of the Floridan aquifer are less than 150 ppm in the western part of the county, 150 to 300 ppm in the central part of the county, 300 to 2,000 ppm in most of the eastern part of the county, and over 2,000 ppm in a narrow strip along the St. Johns River at the eastern border of the county. The salty water in the aquifer is believed to be residual sea water that entered the aquifer the last time Florida was under the sea and has not been completely flushed. There is no evidence that sea water is currently (1964) encroaching into Orange County.
The nonartesian aquifer is composed of sand generally within 40 feet of the surface. This aquifer will usually yield enough water for domestic supplies, stock watering, and lawn irrigation. The dissolved solids content of water from the nonartesian aquifer is usually lower than that of the Floridan aquifer but it is often high in color and iron content. The nonartesian aquifer is recharged by local rainfall and discharges mostly by seepage into lakes and streams, by downward seepage into underlying aquifers, and by evapotranspiration.
The secondary (shallow) artesian aquifers are discontinuous permeable beds of porous sand, gravel or shell. The yield of wells in these aquifers varies greatly with the character of the bedsat some sites large supplies can be developed, but usually yields are moderate to small. The shallow artesian aquifers are recharged by downward leakage from the water table where the water table is above the piezometric surface and by upward leakage from the Floridan aquifer where the piezometric surface is above the water