This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 1994. The map is based on water-level measurements made at more than 900 wells and springs. Ninety-two new wells were added to the September 1994 map--42 in southern Georgia and 50 in Florida. Data on the map were contoured using 5-foot contour intervals in most areas. The potentiometric surface of this karstic aquifer generally reflects land surface topography. Potentiometric-surface highs often correspond to topographic highs, which are areas of surficial recharge to the Upper Floridan aquifer. Springs within topographic lows along with areas of more diffuse upward leakage are natural zones of discharge. Municipal, agricultural, and industrial withdrawals have lowered the potentiometric surface in some areas. The potentiometric surface ranged from 131 feet above sea lvel in Polk County to 86 feet below sea level in southern Georgia near the St. Marys River. With the additon of new wells in southern Georgia, water level data now indicate two distinct depressions at industrial well fields near the St. Marys River in southern Georgia and eastern Nassau County where previously there was only one depression indicated. Water levels measured in September 1994 generally were about 0 to 4 feet higher than those measured in September 1993, except in Seminole County, where increases of 1 to 7 feet above September 1993 levels were recorded at most wells. Generally, September 1994 water levels were 1 to to 5 feet higher than levels in May 1994 except in Union, Gradford, Alachua, Levy, and western Marion Counties where levels remained nearly unchanged, and in Seminole and northwestern Orange Counties where water levels generally were 3 to 12 feet higher than levels in May 1994.