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Hydrology and water quality of Delavan Lake in southeastern Wisconsin

Water-Resources Investigations Report 87-4168

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Abstract

Delavan Lake is a eutrophic, recreational lake in a densely populated area of southeastern Wisconsin. Sewage effluent and septic tank drainage were diverted out of the drainage basin of the lake to improve its water quality in 1981. The worst known blue-green algal bloom occurred in the lake in the summer of 1983. A comprehensive hydrologic and water quality investigation was started in October 1983 to determine why the water quality in the lake apparently had not improved after cessation of influxes of wastewaters. The in-lake phosphorus mass during the 2-year study shows a gradual declining trend that suggests an improving lake condition but also could be due to a random phosphorus decline. Future monitoring will be needed to determine whether the decline in phosphorus has indeed occurred as a result of wastewater diversion. Continuous streamflow and water quality monitoring in the subbasins of the Delavan Lake watershed showed a wide range of annual phosphorus and nitrogen yields during the study. Jackson Creek tributary, which predominantly drains the city of Elkhorn, had the highest average yields of phosphorus (838 pounds/sq mi) and Kjeldahl nitrogen (3,600 pounds/sq mi). External loading of phosphorus and nitrogen were sufficient to cause eutrophic conditions. Internal loading of phosphorus was more than two times the external phosphorus supply. Most of the internal loading occurred when the hypolimnion was anoxic during summer. Internal loading of phosphorus was more than two times the external phosphorus loadings of phosphorus during the 1985 water year was significantly reduced from that of 1984 because of a shorter anoxic period. (Lantz-PTT)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Hydrology and water quality of Delavan Lake in southeastern Wisconsin
Series title:
Water-Resources Investigations Report
Series number:
87-4168
Edition:
-
Year Published:
1988
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
vi, 107 p. :ill., maps ;28 cm.