A map showing the potentiometric surface of the Floridan aquifer was prepared for that area north and west of Gainesville to near Tallahassee, Florida. Contoured at 10-foot (3.048-meter) intervals and at a scale of 1:500,000, the map illustrates the altitude to which water would rise in tightly cased wells that tap the aquifer as of May 1976. The sites of observation wells used as control are shown. The potentiometric surface slopes southwest toward the Gulf of Mexico and to the Suwannee River and its tributary, the Santa Fe River. (Woodard-USGS)