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Hydrogeology of Southeastern Florida

The hydrology of southeastern Florida is unique because of the dynamic interaction between ground water and surface water. One of the most striking surface-water features in southern Florida is the Everglades, often referred to as the "river of grass," which flows south from Lake Okeechobee to Florida Bay. North of the Tamiami Canal, the Everglades are divided into water-conservation areas (fig. 1). These conservation areas, although originally part of the continuous Everglades "river," are now separated by canals, highways, and levees. South of the Tamiami Canal, the Everglades is uncontrolled in Everglades National Park, which extends to Florida Bay (fig. 1).

The Atlantic Coastal Ridge separates the Everglades from the Atlantic Ocean and Biscayne Bay (fig. 2). The ridge is about 5 to 15 km (kilometers) wide and roughly parallels the coast in the northern half of Miami-Dade County. In southern Miami-Dade County, the Atlantic Coastal Ridge is located farther inland and low-lying coastal marshes and mangrove swamps adjoin Biscayne Bay. Historically, the transverse glades (low-lying areas that cut through the Atlantic Coastal Ridge) allowed high-standing surface water in the Everglades to drain into Biscayne Bay.

Throughout much of the study area, a complex network of levees, canals, and control structures is used to manage the water resources. The major canals, operated and maintained by the South Florida Water Management District, are used to prevent low areas from flooding and prevent saltwater intrusion into the Biscayne aquifer. These water-management canals primarily have been constructed in the low-lying transverse glades to more effectively route surface water toward Biscayne Bay.

Anecdotal evidence suggests that prior to the construction of the canal network in southern Florida, submarine springs discharged ground water into Biscayne Bay. There are historical accounts of sailors lowering buckets into freshwater boils to replenish their potable water supplies. Beginning in the early 1900's, canals were constructed to lower the water table, increase the available land for agriculture, and provide flood protection. By the 1950's, excessive draining lowered the water table 1 to 3 m and caused saltwater intrusion, thus endangering the freshwater resources of the Biscayne aquifer. In response to saltwater intrusion, control structures were built near the mouths of canals to raise inland ground-water levels.

Figure 2. Natural physiographic features of southern Florida (from Parker and others, 1955). [larger image]

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