Abstract Drainage wells include all wells that are used to inject surface water directly into an aquifer, or shallow ground water directly into a deeper aquifer, primarily by gravity. By this definition, drainage wells in Florida may be grouped into two broad types: (1) surface-water injection wells, and (2) interaquifer connector wells. Drainage wells of the first type are further categorized as either Floridan aquifer drainage wells or Biscayne aquifer drainage wells. Effective use of drainage wells requires a source of injection water (a losing aquifer or surface water); prevailing natural downward gradient from the source to the receiving aquifer; and transmission and storage characteristics of the receiving zone that will allow emplacement of the volumes of injection water without head buildup sufficient to decrease severely the downward gradient.
The most common use of Floridan aquifer drainage wells is the supplement surface drainage for urban areas in the karst terrains of topographically higher areas of central and north Florida. Drainage wells are the primary means of urban drainage for the Ocala (35 wells), Live Oak (46 wells), and Orlando (392 wells) areas. Records are available for a total of 607 Floridan aquifer drainage wells. These wells are generally effective as a method of urban drainage and lake level control. In areas so served, they emplace more recharge in the Floridan aquifer than it would receive under natural conditions. Continuing caution, however, is suggested in regard to the water-quality aspects of these wells because they often inject to the same aquifer zones from which public water supplies are withdrawn.
Biscayne aquifer drainage wells are used locally to dispose of storm-water runoff and other surplus water in southeast Florida. More than 5,000 drainage wells have been permitted in Dade County, and there are an estimated 2,000 in Broward County. The majority of these wells are used to dispose of water from swimming pools or to dispose of heated water from air-conditioning units. The remainder are used for disposal of urban runoff or of wastewaters from business and industry in the area. The use of Biscayne aquifer drainage wells may have minimal effect on aquifer potability so long as injection of runoff and industrial wastes is restricted to zones where chloride concentrations exceed 1,500 milligrams per liter.
The predominant use of interaquifer connector wells in Florida is concentrated in the phosphate mining areas of Polk and Hillsborough Counties. These wells serve the dual purposes of facilitating mining operations (by providing drainage) and supplying artificial recharge to the Floridan aquifer. Records are available for 167 interaquifer connector wells in the mining areas of Polk, Hillsborough, and Manatee Counties. Their use should have less effect on ground-water quality than that of surface-water injection wells.