Delavan Lake Rehabilitation Project

In the early 1980s, water quality in Delavan Lake had deteriorated to the point that there were severe blue-green algae blooms and excessive rough fish populations, such as carp and bigmouth buffalo.

The Lake community organized the Delavan Lake Sanitary District, and sewers were constructed around the lake to stop point-source pollution, which was thought to be the cause for poor water quality.  The cost of this system was nearly $50 million.

However, just a few years after completion of the sewer system, water quality deteriorated; there were worse algae blooms causing restrictions on swimming and lake usage.

Again the Lake community rallied and organized a 3-year study with the cooperation of the U.S. Geological Survey and Wisconsin Department of Natural Resources.  The Lake Committee was formed to help the Town manage the Lake.  The University of Wisconsin’s Department of Civil and Environmental Engineering and the Institute of Environmental Studies both contributed research and engineering planning for the rehabilitation project.

By 1989, a comprehensive rehabilitation project began.  Some highlights of the steps taken over the next 3 years include:

  • The Lake’s water level was drawn down by 10 feet in order to facilitate the eradication of the entire fish population.  

  • Three ponds were constructed near Mound Road to help capture sediment coming from Jackson Creek before the water entered the Inlet.

  • A sediment control channel was dredged in the Inlet.

  • The dam at the end of the Outlet was reconstructed.  

  • The bottom of the Lake was treated with alum to trap phosphorus sediments and prevent them from re-entering the Lake.  

  • A peninsula was constructed near Community Park in an effort to divert sediment-laden water from entering the main Lake by redirecting it towards the Outlet.

  • Game fish were restocked as the Lake refilled to its normal level.

  • Costs for these projects were slightly more than $7 million.

The project was a success.  By 1991, water clarity was at 26 feet deep.   Additional projects were undertaken to purchase and restore wetlands.  This effort was one of the nation’s largest lake rehabilitation projects and demonstrated effective partnerships among several federal, state and local governmental agencies, especially the Town of Delavan.  

However, over time the effectiveness of these measures changed.  The Mound Road ponds filled in at a faster rate than expected, causing the need for a dredging project.  The Inlet sediment level also increased.  In 2005, the Town began discussions on new maintenance projects that would restore the sediment-capturing abilities of the Mound Road ponds, dredge sediment out of the Inlet, repair a weir (dam-like structure) and dredge Brown’s Channel, the southern tributary of the Lake.  Long-term goals may include long-range plans to not only complete restoration of the original project, but also develop ongoing maintenance plans to alleviate the necessity for costly larger projects.

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