Home Abstract Introduction Hydrogeology of S. Florida Ground-Water Movement - Movement Based on Natural Isotopes - Flow Patterns - Effects of Rising Sea Level > Upwelling Ground Water Subsurface Storage Summary and Conclusions References PDF Version

Ground-Water Movement in the Floridan Aquifer System in Southern Florida: Upwelling Ground Water as Evidence of Circulation

The existence of upwelling warm, salty ground water in the Upper Floridan aquifer in southern Florida is further evidence that vertical circulation does occur. At least five temperature anomalies in southern Florida have been identified and discussed by various investigators (fig. 25). Most of the reported anomalies are on the southwestern coast of Florida, where the Upper Floridan aquifer is an important source of supply (and consequently there is a higher density of deep artesian wells) and where temperatures in the underlying Lower Floridan aquifer are highest. On the southeastern coast, temperature anomalies in Martin County were first reported by Lichtler (1960, p. 62) and expanded on by Sproul (1977, p. 84); data on temperature and salinity anomalies in St. Lucie County were later reported by Reece and others (1980).

The temperature anomalies in the Upper Floridan aquifer in the Martin County-St. Lucie County area (fig. 26) are indicated by composite temperatures of ground water from wells ranging in depth from about 800 to 1,200 ft, exceeding the background temperature of about 80 °F by as much as 10°F. Temperatures that are above normal occur in wells aligned generally in a northwesterly-southeasterly trend, extending from the northwestern corner of St. Lucie County to the southeastern corner of Martin County. Above-normal temperatures also occur in the vicinity of south-central Martin County. The temperatures of the anomalies compare closely with the temperatures of saltwater in the underlying Boulder Zone of the Lower Floridan aquifer. Also, the salinity (dissolved solids) of the ground water in the Upper Floridan aquifer near the temperature anomalies is locally higher (fig. 27), thereby providing additional evidence of upwelling from the Boulder Zone. The northwesterly-southeasterly trend of the salinity and temperature anomalies suggests that the source likely is water upwelling through sinkholes or vertical solution pipes, which are associated with major linears (fractures or perhaps faults) in the Tertiary limestone. During low stands of sea level, the same features probably facilitated recharge to the underlying Boulder Zone. The presence of brackish ground water with anomalously high carbon-14 activity in the Upper Floridan aquifer in southern Florida also is evidence that upwelling is widespread. The theory of inland circulation of seawater and subsequent mixing with seaward-flowing freshwater is preferred to the theory that saltwater in the Floridan aquifer system in southern Florida is connate or residual seawater from high stands of sea level.