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The primary source of drinking water in much of Florida is the upper Floridian aquifer which lays beneath the surficial aquifer ; however the upper Floridian aquifer is often poorly confined and prone to contamination from the surficial aquifer . The shale separating the upper dolomite aquifer from the underlying sandstone and dolomite aquifers retards hydraulic connection between them . Recharge water entering the upper Floridian aquifer system can remain in the aquifer for more than 20 years before it discharges from a spring . The water is recharged locally from precipitation , and , where the overlying glacial materials are thin , the upper bedrock aquifer is susceptible to groundwater contamination .