Physical and Hydrochemical Evidence for Lake Leakage in Lake Seminole, Georgia
Crilley, Dianna M.
Torak, Lynn J.
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Major ions, nutrients, radon-222, and stable isotopes of hydrogen and oxygen were collected from 30 wells, 7 lake locations, and 5 springs in the Lake Seminole area, southwestern Georgia and northwestern Florida, during 2000. These were used to investigate lake-aquifer interaction including surface water mixing with ground water from the underlying Upper Floridan aquifer, lake leakage beneath Jim Woodruff Dam, and karstic dissolution of the limestone aquifer matrix. Solute and isotopic tracers indicate that in-lake springflow evolves along ground-water and surface-water pathways, and that the fractions of these two source waters present in springflow varies with spring location and season. Leakage from Lake Seminole into the Upper Floridan aquifer is evidenced by upwelling in the channel bottom of the Apalachicola River about 300 yards downstream of the dam, where lake water “boils” up at rates that range from about 140 to 220 cubic feet per second. Dye tracing performed by the U.S. Army Corps of Engineers indicates that this “river boil” receives water from multiple sources that include a similar “boil” on land, which joins flow from a spring-fed ground-water discharge zone before flowing into a sinkhole adjacent to the river. Isotopic data from the river boil indicate about a 13-to-1 mixing ratio of lake water to ground water. The saturation index of calcite in surface-water samples indicates a higher potential for dissolution of the limestone matrix from late fall through early spring than in summer.