Saltwater intrusion in the shallow aquifer in Martin and Palm Beach counties, Florida

Urban growth has been rapid in recent years in Palm Beach and Martin Counties, Fla. The withdrawal of large quantities of fresh ground water in the vicinity of the coast has reduced or locally reversed the natural seaward hydraulic gradient and, in places, allowed saltwater to advance landward in the aquifer, displacing freshwater. Maps show the position of the saltwater front in eight urban areas adjacent to the coast. The saltwater front, as shown on the profiles, is based on a chloride concentration of 250 mg/liter which is recommended as a limit for water that is considered potable. The chloride concentration of native freshwater almost always is less than 50 mg/liter in the coastal aquifer. (Woodard-USGS)