Potentiometric surface of the upper Floridan aquifer in the St. Johns River Water Management District and vicinity, Florida, September 1985

This map shows the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 1985. The Upper 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 of Nassau County, a 40-foot interval is used to show a deep cone of depression. The potentiometric surface ranged from 130 feet above sea level in Polk County to 91 feet below sea level in Nassau County. Water levels in key wells were mostly about 1 foot below average for September but were trending upward in response to the rainfall that broke the drought-like dry season. Most levels in the district were below the levels of September 1984. Declines of 3 to 5 feet from September 1984 levels were common in the midwestern part of the district. However, most September 1985 levels ranged from 2 to 7 feet above those of May 1985. (USGS)