The Floridan Aquifer System (FAS) is one of the world’s most productive and extensive groundwater sources, spanning approximately 100,000 square miles beneath all of Florida and extending into parts of Alabama, Georgia, Mississippi, and South Carolina. Composed primarily of porous limestone and dolomite rock, this immense subterranean reservoir provides the vast majority of the region’s water supply. The FAS is the primary source of drinking water for nearly 10 million people and supports extensive agricultural and industrial operations throughout the southeastern United States. This invaluable resource faces increasing pressure from human activity that threatens both the quantity and quality of its water.
Excessive Water Withdrawal and Declining Levels
The volume of water drawn from the Floridan Aquifer System places unsustainable stress on the resource. Total withdrawals were estimated at over 4 billion gallons per day in the early 2000s, with nearly half dedicated to agricultural irrigation. Rapid population growth fuels this demand, causing withdrawals from public supply wells to increase significantly since the 1970s.
Agricultural use, including large-scale citrus production and turf farming, accounts for a major part of the aquifer’s water consumption. This high rate of extraction often exceeds the natural recharge rate, causing a measurable decline in the potentiometric surface. Long-term data shows a downward trend in water levels and spring flows, with a pronounced decline observed since the 1960s. In areas of concentrated pumping, such as the greater Orlando metropolitan area, water level drawdowns have been simulated to exceed 25 feet under drought conditions.
Saltwater Intrusion Threat
A severe consequence of excessive freshwater withdrawal in coastal regions is saltwater intrusion, an irreversible process that diminishes the usable water supply. This mechanism involves the movement of naturally occurring saline water into the aquifer’s freshwater zones. In a healthy coastal aquifer, the pressure from the lighter, land-based freshwater naturally keeps the denser, underlying saltwater at bay.
When pumping reduces freshwater pressure, this delicate balance is disturbed, allowing the saltwater-freshwater interface to migrate inland and upward. Intrusion occurs through lateral movement from the coast or through upconing, where saltwater is drawn up from deeper saline zones below pumped wells. Coastal areas like northeastern Florida’s Duval and St. Johns Counties are particularly vulnerable, with increased chloride concentrations observed miles inland. This process forces water managers to abandon compromised wells or invest heavily in desalination and alternative water sources.
Sources of Groundwater Contamination
The quality of the Floridan Aquifer is compromised by contaminants entering the system from the surface. The aquifer is vulnerable due to Florida’s extensive karst geology, characterized by porous limestone, sinkholes, and large conduits. These features allow surface water and pollutants to bypass the natural filtration provided by soil layers and move rapidly into the groundwater.
The primary quality issue is nutrient loading, specifically high concentrations of nitrate and phosphate. Agricultural runoff, including fertilizers used on crops and golf courses, is a major source of this contamination, along with septic tanks and wastewater treatment effluent. Nitrates are easily transported into the groundwater where the aquifer is unconfined and close to the surface. Other contaminants, such as pesticides, pharmaceuticals, and industrial waste, also pose a threat, moving quickly through the karst system.
Ecological Impact on Florida Springs and Wetlands
The issues of diminished quantity and quality converge to create a significant ecological impact on Florida’s unique spring and wetland systems. The Floridan Aquifer is the source for over 1,000 springs, including the world’s largest concentration of first-magnitude springs, which are natural discharge points for groundwater. Excessive water withdrawal directly leads to a reduction in spring discharge, with some springs experiencing flow declines of over 30% historically.
This reduced flow disrupts the entire spring ecosystem, leading to a loss of wetland habitats that depend on consistent water discharge. Simultaneously, the influx of nutrients like nitrates from surface contamination fuels the growth of filamentous algae, such as Lyngbya. This algal overgrowth covers spring beds and aquatic vegetation, reducing water clarity and causing extreme fluctuations in dissolved oxygen levels. These changes stress native aquatic life and displace native grasses, signifying the environmental cost placed on the aquifer system.