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

This map shows the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 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 30-foot interval is used to show a deep cone of depression. The potentiometric surface ranged from 125 feet above sea level in Polk County to 74 feet below sea level in Nassau County. Water levels in key wells ranged from 1 to 8 feet below average for May in response to lack of rainfall and an attendant increase in pumpage. Many levels in the district were considerably below the levels of May 1984. Declines of 5 to 7 feet from May 1984 levels were common in the western and northern parts of the district. However, the largest declines from May 1984 levels were mostly in well fields along the coastline. Levels in some wells reached record lows. (USGS)