Potentiometric surface of the Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, May 1982

This map presents the potentiometric surface of the Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1982. The Floridan aquifer is the principal source of potable water in the area. Water-level measurements were made on approximately 1,000 wells and on several springs. The potentiometric surface is shown mostly by 5-foot contour intervals. In the Fernandina Beach area 20-foot intervals are used to show a deep cone of depression. The potentiometric surface ranged from 128 feet above NGVD (National Geodetic Vertical Datum of 1929) in Polk County to 68 feet below NGVD in Nassau County. Because of above average rainfall, water levels began to recover from record low levels set in September 1981 in many counties. Except in a few places, water levels throughout the District rose above May 1981 levels. May 1982 levels were as much as 9 feet and commonly 1 to 3 feet higher than the below normal May 1981 levels. (USGS)