Effects of Point-Source Removal on Lake Water Quality: A Case History of Lake Tohopekaliga, Florida

Abstract

ABSTRACT Lake Tohopekaliga (9,840 ha) is part of the Kissimmee River system headwaters in central Florida. Point source discharges to the lake and its tributaries began in the 1950s. By the early 1960s four municipal wastewater treatment plants were discharging secondary effluent that contained high concentrations of phosphorus and nitrogen. Rapid population growth and treatment plant expansion began in the 1960s, and by 1969 the lake had experienced deterioration of water quality, aquatic habitat, and biological communities. By 1979, annual phosphorus loading to the lake was eleven times higher than under natural conditions and nitrogen loads had nearly doubled. Efforts to reduce phosphorus concentrations in effluent from the two largest point sources began in 1982, followed by complete removal of all wastewater treatment plant discharges by 1988. Ten years later, Lake Tohopekaliga had experienced reductions in total phosphorus (80 percent), ortho-phosphorus (95 percent), total nitrogen (50 percent), and chlorophyll a (30 percent). Secchi disk transparencies increased an average of 50 percent. Measurable improvements in water quality were also documented for downstream lakes Cypress, Hatchineha, and Kissimmee. No water quality changes were noted in neighboring East Lake Tohopekaliga, which served as a comparison lake for this study.