Cooperator: Delavan Lake Sanitary District
Project Chiefs: Dale M. Robertson; Gerald L. Goddard
Location: Walworth County
Project Number: 9KB33
Period of Project: August 1983–Continuing
 Problem
Eutrophication of Delavan Lake accelerated from the 1940s to 1980s, resulting in a hypereutrophic lake with severe blue-green algae blooms. Extensive rehabilitation efforts were implemented from 1990–1993 to improve the lake’s water quality. Monitoring of the lake and nutrient and sediment loads to the lake is continuing to determine the effectiveness of rehabilitation efforts and guide future management decisions.
Objective
The objectives of this project are to:
(1) quantify the effectiveness of rehabilitation efforts by measuring nutrient and suspended sediment loads at Jackson Creek tributary near Elkhorn, Jackson Creek at Mound Road (wetland outlet), Delavan Lake Inlet at Highway 50, and at the lake’s outlet,
(2) measure water quality, and plankton populations in the lake, and
(3) determine the trapping efficiency of the upstream wetlands for phosphorus and suspended sediment.
Approach
Nutrients, suspended sediments, and streamflow are monitored at Jackson Creek tributary, the wetland outlet at Mound Road, at Highway 50, and the lake outlet. Nutrient concentrations, dissolved oxygen, water temperature, pH, specific conductance, and planktonic populations are monitored within the lake. The effectiveness of the wetland is estimated by examining changes in the morphometry of the wetland ponds and changes in phosphorus and suspended sediment export at Mound Road.
 Progress (July 2003–June 2004)
Streamflow was monitored continuously at three inflow sites and at one outflow site. Water samples were collected monthly and during storm-runoff events at all stream sites. Water samples were collected at the center of the lake and analyzed for nutrients and plankton populations. The 2003 water-year data were compiled and published in USGS annual reports, “Water Resources Data–Wisconsin, Water Year 2003” and “Water-Quality and Lake-Stage Data for Wisconsin Lakes, Water Year 2003.” Although summer average total phosphorus concentrations have increased since 1993 (to about 40 µg/L), chlorophyll a concentrations remain relatively low and water clarity remains very good. Additional sediment deposition was measured in the wetland ponds.
Plans (July 2004–June 2005)
Reconfiguration of the wetlands is planned for this period. The monitoring program for the tributaries and the lake will be continued and the effects of changes to the wetland will be documented. Data will be compiled for publication.
Reports
Robertson, D.M., Goddard, G.L., Helsel, D.R., and MacKinnon, K.L., 2000, Rehabilitation of Delavan Lake, Wisconsin: Lake and Reservoir Management, v. 16, no. 3, p. 155–176.
Panuska, J.C., and Robertson, D.M., 1999, Estimating phosphorus concentrations following alum treatment using apparent settling velocities: Lakes and Reservoir Management, v. 15,
no. 1, p. 28–38.
Robertson, D.M., Elder, J.F., Goddard, G.L., and James, W.F., 1998, Dynamics in phosphorus retention in wetlands upstream of Delavan Lake, Wisconsin: Lakes and Reservoir Management, v. 14, no. 4, p. 466–477.
Elder, J.F., Manion, B.J., and Goddard, G.L., 1997, Mesocosm experiments to assess factors affecting phosphorus retention and release in an extended Wisconsin wetland: U.S. Geological Survey Water-Resources Investigations Report 97–4272, 14 p.
Goddard, G.L., and Elder, J.F., 1997, Retention of sediments and nutrients in Jackson Creek Wetland near Delavan Lake, Wisconsin, 1993–95, U.S. Geological Survey Water-Resources Investigations Report 97–4014, 22 p.
Elder, J.F., and Goddard, G.L., 1996, Sediment and nutrient trapping efficiency of a constructed wetland near Delavan Lake, Wisconsin, 1993–1995: U.S. Geological Survey Fact Sheet 232–96.
Robertson, D.M., Field, S.J, Elder, J.F., Goddard, G.L., and James, W.F., 1996, Phosphorus dynamics of Delavan Lake inlet in southeastern Wisconsin: U.S. Geological Survey Water-Resources Investigations Report 96–4160, 18 p.
Field, S.J., and Duerk, M.D., 1988, Hydrology and water quality of Delavan Lake in southeastern Wisconsin: U.S. Geological Survey Water-Resources Investigations Report 87–4168, 61 p. |
