publications > circular > Circular 1134 > water and environmental stress > degradation of water quality > charlotte harbor watershed U.S. Department of the Interior U.S. Geological Survey Circular 1134 Water and Environmental Stress Water and Environmental Stress Charlotte Harbor Watershed Much of the Charlotte Harbor watershed has been altered by human activities. Streamflow has declined significantly during 1934-84 in sections of the Peace River, probably as a result of ground-water pumping in the upper basin. Nutrient concentrations generally have increased in the rivers over the last 15 years because of an increase in wastewater effluent and agricultural runoff. In 1984, 114 facilities were permitted to discharge domestic or industrial effluents to waters tributary to Charlotte Harbor. One of these facilities is in the Myakka River Basin, 11 are in the coastal basin, 14 are in the Caloosahatchee River Basin, and 88 are in the Peace River Basin. Citrus and phosphate-ore processing account for most of the industrial effluent. Several locations in the headwaters of the Peace River show significant effects of receiving wastewater effluent. At some locations, dissolved-oxygen concentrations were lower than 2.0 mg/L, which is the minimum State standard for any class of surface water (Hammett, 1990). The water quality of several lakes in the headwaters of the Peace River has been affected by citrus-processing effluent (Hammett, 1990). Citrus processing produces a strongly buffered, high carbon waste that can contain inorganic debris from washing, and can have a residue of pesticides and toxic peel oils (Lackey, 1970). The degradation of the waste produces objectionable odors and a high biochemical oxygen demand. Citrus production involves the use of numerous chemicals that include fertilizers, insecticides, herbicides, and fungicides. Benomyl, bromocil, diuron, dicofol, chlorobenzilate, ethylene dibromide, and aldicarb have been used or are currently in use. The trace elements copper, manganese, and zinc also are applied to citrus (Rutledge, 1987). Runoff or ground-water seepage from citrus groves has the potential of transporting any of these substances to the stream system. The concentrations of phosphorus are naturally high in the Peace River because of extensive phosphate deposits in its basin. The phosphate deposits also are rich in radionuclides of the uranium-238 series, including radium-226. In the upper basin, these deposits are exposed in the riverbed. Extensive phosphate mining and processing have exposed additional deposits to surface runoff. Periodic spills of phosphate industry sediments are caused by the structural failure of retaining dikes and have resulted in the discharge of clayey wastes, known as slime, to the Peace River and has contributed additional phosphorus and radium-226 to the river and estuary. A single spill can contribute a phosphorus load equal to the annual loading in the Peace River at Arcadia (Miller and McPherson, 1987). The effects of these slime spills have been seen as long as 2 years after the event (Martin and Kim, 1977). In phosphate ore processing plants, a mixture of organic chemicals, which include kerosene and fuel oil, is used to facilitate separation of phosphate ore from unwanted sands and clays. Runoff from sand tailings may represent diffuse sources of organic-chemical contamination (Rutledge, 1987). The chemical processing of phosphate ore into phosphoric acid produces a highly acidic process water. Organic chemicals, which include phenols, also are used in processing. The gypsum stacks, cooling ponds, and recirculation ditches of the chemical-processing plants are a potential source of contamination of the surficial aquifer (Miller and Sutcliffe, 1984). Runoff from phosphate mines may increase turbidity and significantly reduce light in the receiving bodies of water (Miller and Morris, 1981). There are other potential sources of nutrient and pollutant loads to the Charlotte Harbor watershed. Ground-water inflow to the rivers and Charlotte Harbor is an apparent source of radium-226 (Miller and Sutcliffe, 1985; Miller and others, 1990). Background levels of radium-226 in the rivers and Harbor reported by Miller and others (1990) are an order of magnitude higher than those found in other parts of the United States (Elsinger and Moore, 1980; 1983; 1984). Runoff from pastures and cropland carries nutrients and, in some cases, pesticides to the river system. Septic-tank drainfields are another source of nutrients and a potential source of bacterial contamination. Runoff from urban areas may carry heavy metals, nutrients, bacteria, viruses, and pesticides. Marinas contribute oil and gas, as well as wastewater and metals, to the rivers and estuarine system. Rainfall and dustfall bring contaminants and nutrients by air to the river system and estuary. Numerous deep wells under high artesian pressure, drilled into the Floridan aquifer system many years ago, have been a source of brackish water contamination of shallow aquifers in southwestern Florida and south of Lake Okeechobee (Parker and others 1955; McCoy, 1972). These wells were not cased deeply enough or else the casings have corroded, allowing brackish water that is under pressure from the Floridan aquifer system to move upward along open well bores or through corroded sections and seep outward to contaminate large parts of shallow aquifers (Klein and others, 1964; Sproul and others, 1972). Next: Mercury contamination in south Florida Go to top Return to Publications Page

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