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Hydrogeology and the Distribution and Origin of Salinity in the Floridan Aquifer System, Southeastern Florida

Water-Resources Investigations Report 94-4010
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https://doi.org/10.3133/wri944010

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Abstract

The Floridan aquifer system in southeastern Florida consists of the Upper Floridan aquifer, the middle confining unit, and the Lower Floridan aquifer. An upper zone of brackish water and a lower zone of water with a salinity similar to that of seawater are present in the Floridan aquifer system. The brackish-water zone is defined as that in which water has a dissolved-solids concentration of less than 10,000 milligrams per liter (chloride concentration less than about 5,240 milligrams per liter), and water in the the saline-water zone has a dissolved solids concentration of about 35,000 milligrams per liter (about 18,900 milligrams per liter chloride concentration). The brackish-water and saline-water zones are separated by a transitional zone, typically 100 feet thick, in which salinity increases abruptly with depth. The base of the brackish-water zone lies within the Upper Floridan aquifer along the coast but extends into the middle confining unit inland. The brackish- water zone is as much as 1,200 feet thick inland, whereas the Upper Floridart aquifer is typically 500 to 600 feet thick. Changes in lithology or permeability do not usually control the position of the boundary between the brackish-water and saline-water zones. Calculations of the depth of a brackish-water and saline-water interface using the Ghyben-Herzberg relation show good agreement between calculated and actual positions of the interface, indicating equilibrium between the zones. Several areas of high salinity with chloride concentrations greater than 3,000 milligrams per liter are present in the upper interval of the brackish-water zone near the coast, and in one of these areas in northeastern Broward County, salinity decreases with depth from the upper to lower interval. The high salinities could be a result of seawater preferentially encroaching into zones of higher permeability in the Upper Flofidan aquifer during Pleistocene high stands of sea level and incomplete flushing of the seawater by the present-day flow system.

Suggested Citation

Reese, R.S., 1994, Hydrogeology and the distribution and origin of salinity in the Floridan aquifer system, southeastern Florida: U.S. Geological Survey Water-Resources Investigations Report 94-4010, vi, 56 p., https://doi.org/10.3133/wri944010.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Hydrogeology and the distribution and origin of salinity in the Floridan aquifer system, southeastern Florida
Series title Water-Resources Investigations Report
Series number 94-4010
DOI 10.3133/wri944010
Year Published 1994
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Caribbean-Florida Water Science Center
Description vi, 56 p.
Country United States
State Florida
Other Geospatial Floridan aquifer system
Additional publication details