Florida Water Science Center
Floridan Aquifer System Groundwater Availability Study
The U.S. Geological Survey Groundwater Resources Program is assessing groundwater availability in areas of critical importance across the Nation. The Floridan Aquifer System Groundwater Availability Study is being conducted as a part of this program. This regional study of the Floridan aquifer system will provide numerous benefits, including an updated hydrogeologic framework, regional and subregional water budgets, and a modern, system-wide, groundwater flow model that may be used to quantitatively assess the effects of human and environmental stresses. The Floridan Aquifer System Water Availability Model (FASWAM) will be a key tool developed during the study.
The Floridan aquifer system covers approximately 100,000 square miles in the southeastern United States in Florida and portions of Georgia, Alabama, Mississippi, and South Carolina. It is a sequence of carbonate rocks over 3,000 feet thick in south Florida and thins towards the north. Typically split into the Upper Floridan aquifer, the middle confining unit, and the Lower Floridan aquifer, the majority of freshwater is contained in the Upper Floridan aquifer and is used for water supply (Miller, 1986, 1997). The Lower Floridan aquifer contains fresh to brackish water in northeastern Florida and Georgia, while in south Florida it is saline and used to dispose of effluent from wastewater treatment processes.
Precipitation in the southeastern United States is around 53 inches per year. The majority of recharge to the Floridan aquifer system, approximately 10 to 25 inches per year, occurs from rainfall in the areas where it is unconfined or semi-confined, whereas in the areas of confinement the recharge is less than 1 inch per year (Bush and Johnston, 1988; Sepulveda, 2002). Natural discharge to streams and lakes occurs through springs or to the ocean through submarine groundwater discharge (Stewart, 1980). Florida alone has 33 first-magnitude springs, each discharging more than 64.6 million gallons per day (Spechler and Schiffer, 1995).
The Floridan aquifer system is a key source of potable water in the southeastern United States. Groundwater wells for water supply from the Floridan aquifer system were first drilled in the late 1800s. In the early 2000s, the Floridan aquifer system supports almost 10 million people as their primary source of water and is one of the most productive aquifers in the world (Marella and Berndt, 2005; Miller, 1990). Water from the Floridan aquifer system is used for public, domestic, and industrial water supply, with almost 50 percent of water being used for irrigation (Marella and Berndt, 2005).