Lake Operations

Lake Operations Overview

In the 1940s, Delavan Lake experienced a severe decline in water quality which drastically affected the health of the lake's fishery as well as the ability of the residents of the community to enjoy recreational use of the lake. Severe blue-green algae blooms were experienced as well as excessive rough fish populations of carp and bigmouth buffalo. As a result of this deterioration, the numbers of aquatic plant species decreased from 14 in 1948 to less than three in 1975. The causes of this water quality decrease were primarily development, wastewater discharges and failing septic systems.

Citizen concerns for the water quality in Delavan Lake were the major reason for the creation of the Delavan Lake Sanitary District (DLSD) in 1969. This was the first step in providing sewerage systems for the properties around Delavan Lake. This collection system would eliminate the lake pollution caused by the numerous failing septic drain field systems around the lake.

In 1973, DLSD assumed the responsibility for the aquatic nuisance control program on Delavan Lake. Periodic chemical treatments for nuisance algae were conducted by DLSD and this activity led to DLSD's direct involvement with other water quality projects.

In 1979 DLSD began construction of a sanitary sewer system around the lake. During the two year construction period over 39 miles of sanitary gravity collection pipes, 13 pumping stations and more than five miles of force main were constructed. This system would provide centralized treatment of sanitary sewage effluent from about 2,000 homes and businesses around the lake.

Lake area residents led local communities to form a regional wastewater treatment solution to the point source pollution in the watershed. The original interceptor sewer system connected four municipalities to a new regional wastewater treatment facility located downstream of Delavan Lake. By January 1982, discharges from all upstream wastewater treatment plants were diverted and all homes and businesses along the lakeshore were sewered. In spite of all this work, during the summer of 1983, Delavan Lake's water quality was ranked as the worst in the state. Extensive algae blooms and turbid waters resulted in poor fish and wildlife habitat and degraded recreational and aesthetic values.

As a result of the poor water quality, the local community in cooperation with the Wisconsin Department of Natural Resources (WDNR), the University of Wisconsin-Madison Water Resource Management Graduate Program (WRMG) and the U.S. Geological Survey (USGS) began to take steps to identify and correct the lake's problems. In 1983, the USGS and DLSD began a comprehensive investigation of the hydrology and water quality of Delavan Lake. Utilizing the results of the USGS study, the WRMG, in 1986, identified the major external and internal sources of phosphorus and developed a management plan to restore the lake's water quality. The recommended plan included total fishery restoration, an alum treatment, wetland restoration/creation, short-circuiting of lake inflow to the outlet and implementation of urban and rural best management practices to reduce not-point source pollution.

September 5, 1989 marked the beginning of a major restoration project on Delavan Lake as the recommended plan was implemented. The lake level was lowered nearly 10 feet to accomplish total fishery eradication in the watershed. Modifications were made at the dam and an in-lake barrier was constructed to facilitate short-circuiting of lake inflow from the Inlet.

During this period of reduced lake level the Inlet would freeze all the way to the bottom and thus in the spring vast amounts of Inlet bottom sediment would be carried into the lake. This channel was dredged so that during this construction period there would be enough depth for water to flow to the lake without washing in more sediment.

Sediments in the deeper portions of the lake received an alum treatment which was designed to "lock up" Phosphorus in the water column and take it to the lake bottom. It was intended that the Alum would create a "seal" over the lake bottom which would help reduce the amount of sediment Phosphorus that could re enter the water column.

In 2002 the Southeastern Wisconsin Regional Planning Commission completed "A Lake Management Plan for Delavan Lake". The stated intent of this plan was to "evaluate the combined effects of the various lake management measures implemented in and around Delavan Lake since the early 1980s, and to provide direction for future lake management actions to be carried out by the Town of Delavan and its partner agencies. This lake management plan represents an ongoing commitment by the Town of Delavan, the Delavan Lake Sanitary District, the Wisconsin Department of Natural Resources, the U.S. Fish and Wildlife Service, the U.S. Army Corps of Engineers, the U.S. Geological Survey, the University of Wisconsin and the private sector to sound environmental planning".

Quoted from this document's Introduction: "The primary objectives which this plan is intended to achieve are: 1) to contribute to the overall conservation and wise use of Delavan Lake through the environmentally sound management of vegetation, fishes, and wildlife populations in and around the Lake; 2) to provide the potential for high-quality, water-based recreational experiences by residents and visitors to the lake; 3) to effectively control the severity of nuisances resulting from the recurring excessive aquatic macrophyte and algal growths in portions of the Delavan Lake basin; and 4) to facilitate the conduct of water-based recreational activities, to improve the aesthetic value of the Lake, and to enhance its resource value. This plan should serve as a practical guide over time for achieving these objectives in a technically sound manner."

It has and will continue to guide us. 

DLSD Area Map


Sensitive Areas