Eagle Lake Pollution Control Project: Assessment of Lake Improvement

Abstract

In this study of the response of Eagle Lake, Kandiyohi County, MN, to the removal of septic effluent, detailed studies of the biological, chemical, sedimentological, hydrological and physical conditions in the lake were conducted. Comparisons of the data collected in this fifth year study were made with benchmark data. An annual hydrologic budget for Eagle Lake was prepared for the 1978 water year. Results show that the amount of water that flowed through Eagle Lake in the 1978 water year was 6,719 acre-feet. Inflow to the lake comprised 45 percent surface water, 22 percent groundwater, and 33 percent precipitation. Water out of the system comprised 72 percent surface water, less than 1 percent groundwater, 25 percent evaporation, and slightly greater than 2 percent net change in lake storage. Several observations give evidence of an improvement in the quality of Eagle Lake waters after the installation of a peripheral sewage collection line. One such observation is the decrease in total nutrient loads of nitrogen and phosphorus at the spring turnover 1978. However, increases in the phytoplankton biomass and the shifts in the most abundant species with the Blue-Green algae assuming dominance do no t indicate an improvement in water quality. The interpretation of our observations has been compiled by the increased nutrient load of the surface water inlets, especially that which resulted from unseasonably heavy rains flushing large quantities of nutrient rich and biologically active waters stored behind a beaver dam during weeks 24 to 28, 1978.