The potentiometric surface and water quality of the Floridan aquifer; in southwest Hillsborough County, Florida, 1952-74

Large ground-water withdrawals and a 10-year period of below-normal rainfall have caused the potentiometric surface of the Floridan aquifer to decline more than 10 feet (3 metres) in most of a 200-square-mile (520-square-kilometre) area of southwest Hillsborough County (fig. 1). The lowered ground-water levels and the consequent threat of salt-water intrusion concern farmers and residents who depend on ground water for irrigation and domestic purposes. Extensive crop irrigation is continuing; small towns such as Ruskin, River-view, Sun City Center, and Apollo Beach are rapidly expanding; and new communities are being planned. In addition, there are plans to mine the extensive phosphate deposits a few miles east of this heavily-f armed area. All these activities require large supplies of fresh ground water.

The Hillsborough County Commission cooperated with the U. S. Geological Survey to study changes of water levels and water quality in southwest Hillsborough County. The purpose of this report is to compare the position of the potentiometric surface in 1953 with that in 1973 and to show chloride and sulfate concentrations in ground water in 1974.