had already occurred in Fernandina and Jacksonville and south along the east coast of Florida, as well as from Tampa south to Fort Myers on the west coast. Over time, the number of wells increased, as did the finished depths, as demand increased. Industrial supply for pulp and paper mills became a large proportion of the water withdrawn starting in the late 1930s. In the 1950s, all municipal, domestic, and industrial supply (except cooling), and about half of agricultural supply in Orlando, Florida had been converted to groundwater from the Floridan aquifer system. Groundwater withdrawals from the Floridan aquifer system increased steadily from 630 Mgal/d () in 1950 to 3,430 Mgal/d () in 1990. Permitting and regulations enacted during the 1990s curtailed the year-on-year increases in withdrawal; however, withdrawals in 2000 increased to 4,020 Mgal/d () due to extreme drought conditions between 1999 and 2001 that prevailed over much of the Southeastern United States. Much of the increase was due to increased agricultural demand. Location The Floridan aquifer system spans an area of about in the southeastern United States and underlies all of Florida and parts of southern Alabama, southeastern Georgia, and southern South Carolina. The Upper Floridan aquifer contains freshwater over much of its extent, though is brackish and saline south of Lake Okeechobee. The Floridan aquifer system crops out in central and southern Georgia where the limestone, and its weathered byproducts, are present at land surface. The aquifer system generally dips below the land surface to the south where it becomes buried beneath surficial sand deposits and clay. In areas depicted in brown in the image at the right, the Floridan aquifer system crops out and is again exposed at land surface. These regions are particularly prone to sinkhole activity due to the proximity of the karstified limestone aquifer to land surface. Some of the fractures/conduits within the aquifer are large enough for scuba divers to swim through. Hydrology and geology The carbonate rocks that form the Floridan aquifer system are of late Paleocene to early Oligocene age and are overlain by low-permeability clays of Miocene age (upper confining unit) and surficial sands of Pliocene and Holocene age (surficial aquifer system). In west-central Florida, north Florida, and along the updip margin of the system, the limestone crops out and the aquifer system is unconfined. Where low-permeability clays of the upper confining unit are present and substantial, the system