Water quality of Nippersink Creek and Wonder Lake, McHenry County, Illinois, 1994-2001

Wonder Lake, McHenry County, Illinois was formed when an earthen dam was constructed across Nippersink Creek in 1929. The U.S. Geological Survey (USGS), in cooperation with the McHenry County Soil and Water Conservation District, operated two streamflow and water-quality monitoring sites (upstream and downstream of Wonder Lake) from July 1994 through June 1997, and examined the water quality of the lake during 1999-2000. From 1999 through 2001, the USGS National Water-Quality Assessment Program operated the same upstream monitoring station to assess the streamflow, sediments, nutrients, and other chemical and physical characteristics of Nippersink Creek. Interpolation and regression methods were used to compute loads of sediment and nutrients delivered to Wonder Lake through Nippersink Creek by the combination of data sets collected as part of these studies. Since the formation of Wonder Lake, sediment and nutrient loading from Nippersink Creek has caused lake water-quality degradation. Wonder Lake effectively trapped 75 percent of the 15,900 tons of suspended sediment delivered during 1994-97. The average daily sediment load delivered during 1994-2001 was 25 tons. High sediment loading from the watershed reduces water clarity and hinders lake navigation. Nutrient loading from Nippersink Creek results in eutrophic conditions within Wonder Lake as evaluated on a Trophic State Index. The load of total phosphorus trapped in Wonder Lake is from 6 to 28 percent of the delivered load from Nippersink Creek. If the lake could be restored to its original capacity, the sediment trapping efficiency may be increased.