WATER-QUALITY IN THE SHINGLE CREEK BASIN, FLORIDA, BEFORE AND AFTER WASTE-WATER DIVERSION

Shingle Creek is a major inflow to Lake Tohopekaliga, Florida. Water quality and the trophic status of Lake Tohopekaliga are affected strongly by the water quality of Shingle Creek. This report documents 10 yr of water quality data in Shingle Creek at the lake outfall; for a pre- (October 1981-December 1986) and a post-wastewater discharge (January 1987-September 1991) removal period. Nutrient budgets for the subbasins were calculated from an intensive research program (January 1983-December 1985) to document instream impacts attributable to wastewater, determine the role of the cypress swamp in the middle subbassin, and document relationships between water quality and land uses. Rapid urbanization converted forested uplands and agricultural lands to housing and commercial land use during the study. Stormwater runoff in Florida has been identified as a major pollution source. Treatment of stormwater pollution, through Best Management Practices (BMPs), has been regulated by the State of Florida in this area since 1982. By 1988, 84% of the urban landuse in the upper basin was subject to stormwater treatment prior to being discharged to the creek. Potential increases in urban derived nutrient inputs were offset by stormwater management, and alum treatment and diversion of municipal wastewater. Nitrogen loads, and P loads and variance decreased significantly during the 10-yr period, despite rapid urbanization in the northern and central subbasins. Nutrient export from the subbasins was influenced by the dominant land use. The middle subbasin contains a swamp that contributed the greatest P and Cl- loads because of the increase in discharge to the swamp from sources other than the canal. The northern urban subbasin received the wastewater discharges and served as a net sink for N and P exported from the subbasin.