Hydrogeology of the surficial and intermediate aquifers of central Sarasota County, Florida

The hydrogeologic units underlying a 300-square-mile area in central Sarasota County, Florida, consist of the surficial aquifer, intermediate aquifers (Tamiami-upper Hawthorn and lower Hawthorn-upper Tampa aquifers) and confining units, the Floridan aquifer system, and the sub-Floridan confining unit.The saturated thickness of the surficial aquifer ranges from about 40 to 75 feet and the water table is generally within 5 feet of land surface.The Tamiami-upper Hawthorn is the uppermost intermediate aquifer.The top of the aquifer ranges from about 50 feet to about 75 below sea level and has an average thickness of about 100 feet.The lower Hawthorn-upper Tampa aquifer is the lowermost intermediate aquifer.The top of the aquifer ranges from about 190 to about 220 feet below sea level and its thickness ranges from about 200 to 250 feet.The quality of water in the surficial and the two intermediate aquifers is acceptable for potable use except near the coast.Water from the Floridan aquifer system is used primarily for agricultural purposes because it is too mineralized for most other uses; therefore, the surficial and intermediate aquifers are developed for water supply.The artesian pressure of the various aquifers generally increases with depth.A more detailed hydrogeologic description is presented for the Ringling-MacArthur Reserve, a 51-square-mil e area in the central part of the county that may be used by Sarasota County as a future water supply.Average annual rainfall is 56 inches and evapotranspiration is about 42 inches at the Reserve.The area has a high water table, many sloughs and swamps, and undeveloped land, making it an attractive site as a potential source of water.