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<br /> <br />ground water downgradient from Lake Barco, and (4) deeper <br />ground water beneath Lake Barco. Oxygen-rich lake water <br />moving through the organic-rich lake sediments is reduced, <br />resulting in discharge of oxygen-depleted water into the <br />ground water beneath Lake Barco. This downward-moving <br />ground water may have an undesired effect on the chemical <br />quality of ground water in the underlying Upper Floridan <br />aquifer, which is the principal source of water supply for the <br />region. The patterns of ground-water movement determined <br />from hydraulic-head data were corroborated by chemical <br />tracers. For example, the dates that ground water in different <br />parts of the flow system was recharged, as determined from <br />CFC dating, show a fairly consistent increase in the length of <br />time since recharge with depth (Figure L-2C). <br /> <br /> <br />-. . ,,.. <br /> <br />~ <br /> <br />Lake Barco, Florida. (Photograph by Terrie Lee.) <br /> <br />Figure L-2. Lake Barco. in northern Florida, is a flow-through <br />lake with respect to ground water (A and B). The dates that <br />ground water In different parts of the ground-water system <br />was recharged indicate how long it takes water to move from <br />the lake or water table to a given depth (C). (Modified from <br />Katz, B.G., Lee, T.M., Plummer. L.N.. and Busenberg, E., <br />1995. Chemical evolution of groundwater near a sinkhole <br />lake, northern Florida, 1. Flow patterns, age of groundwater, <br />and influence of lake water leakage: Water Resources <br />Research, v. 31, no. 6, p. 1549-1564.) <br /> <br />A <br /> <br />82001' <br />29041' <br /> <br />82000'30" <br /> <br />82' <br /> <br />-101- WATER TABLE AlTITUDE--ln feet above sea level. <br />Contour interval is variable <br />DIRECTION OF GROUND~WATER FLOW <br />. WELL LOCATION <br />83 ALTITUDE OF LAKE SURFACE-In feet above sea level <br /> <br /> <br />. <br /> <br />--70, <br /> <br />80 <br /> <br />Long <br />Lake <br />82 <br /> <br />B EXPLANATION <br />D ORGANIC-RICH SEDIMENTS <br />82 - EQUIPOTENTIAL LINE-In feet above sea level <br /> <br />FEET <br />150 <br /> <br />DIRECTION OF GROUND-WATER FLOW FEET <br />PIEZOMETER 150 <br /> <br />. <br /> <br />'00 <br /> <br />1PNB <br />well <br />nest <br />Water ~ b <br />.--__ a Ie Lake Barco <br />:-~---- -- . ~-~------- <br />- ~--- <br />B3 -~....... . '-_ // <br />82 "'" Surficial sand' . <br />81.2 ~ __/ . <br />79.5 <br />79 <br /> <br />SEA <br />lEVEL <br /> <br />2PNB <br />well <br />nest <br /> <br />'00 <br /> <br />so <br /> <br />50 <br /> <br />SEA <br />LEVEL <br /> <br />. <br /> <br />77 <br /> <br />Bedrock <br /> <br />-so <br /> <br />-50 <br /> <br />VERTICAL SCALE GREATLY EXAGGERATED <br /> <br />o <br /> <br />500 FEET <br />, <br /> <br />c <br /> <br />EXPLANATION <br />D ORGANIC-RICH SEDIMENTS <br />1987. WELL LOCATION-Number is the year <br />that ground water at that location <br />was recharged <br /> <br />FEET <br />150 <br /> <br />FEET <br />150 <br /> <br />'00 <br /> <br />-~':'~~ table <br />1987--;--- <br /> <br />1986 <br /> <br />. --~-196j-- <br />1973 <br />.1:..6~_ <br />/~ <br />,,/ .1962 <br />_..../' .1959 <br />.1958 <br /> <br />SEA <br />lEVEL <br /> <br />Lake Barco <br /> <br />100 <br /> <br />. <br /> <br />. <br />1986 <br /> <br />50 <br /> <br />. <br />1964 <br />Surficial sand <br /> <br />50 <br /> <br />----.. <br />1981 ........... <br />" <br />. " <br />, <br /> <br />------ <br /> <br />SEA <br />LEVEL <br /> <br />1978 <br />. <br /> <br />Bedrock <br /> <br />-so <br /> <br />-50 <br /> <br />VERTICAL SCALE GREATLY EXAGGERATED <br /> <br />o <br /> <br />500 FEET <br />, <br /> <br />53 <br />