Potentiometric surface of the Floridan aquifer, southwest Florida Water Management District, September 1981

A September 1981 potentiometric-surface map of the Southwest Florida Water Management District depicts the annual high water-level period. Water levels in most wells measured in September 1981 are equal to or higher than in May 1981. Levels averaged about 26 feet higher in the southern part of the area and 5 feet in the north. In the agricultural sections of southern Hillsborough, Hardee, southwestern Polk, northwestern De Soto, and Manatee Counties, water levels increased 10 to 46 feet. From September 1980 to September 1981, water levels ranged from a decrease of 11 feet in Citrus County to an increase of 9 feet in southern Hillsborough County. (USGS)