Water sediment, and nutrient budgets, and bathymetric survey of Old and New Gillespie Lakes, Macoupin County, Illinois, May
1996-April 1997; with a discussion of lake-management practices
Dataset Identification:
Resource Abstract:
The Gillespie Lakes system serves as a drinking water source for the town of Gillespie, Illinois, and is a major recreational
focus for the area. As part of an investigation of a concern that the lakes are being adversely affected by excessive sediment
and nutrient in flows, this report presents hydrologic, sediment, and nutrient budgets for Old Gillespie Lake and New Gillespie
Lake, calculated by the U.S. Geological Survey with data collected during May 1996-April 1997 in cooperation with the Illinois
Environmental Protection Agency and the city of Gillespie, Illinois. Bathymetric data also were collected in the two lakes
to produce maps of the lake bed elevations. The influx of sediment, phosphorus, and nitrogen into Old Gillespie Lake during
the study period was 4,063, 6.02, and 52.3 tons, respectively. Old Gillespie Lake retained 92 percent of the inflowing sediment
(which agrees with theoretical calculations of trapping efficiency for Old Gillespie Lake), 84 percent of the inflowing phosphorus,
and 87 percent of the inflowing nitrogen. The influx of sediment, phosphorus, and nitrogen into New Gillespie Lake during
the study period was 4,792, 7.56, and 64.3 tons, respectively. Old Gillespie Lake retained 95 percent of the inflowing sediment
(which agrees with theoretical calculations of trapping efficiency for New Gillespie Lake), 82 percent of the inflowing phosphorus,
and 81 percent of the inflowing nitrogen. The loads per area of phosphorus and nitrogen to the Gillespie Lakes were 1.06 tons/mi2
and 9.26 tons/mi2, respectively. For row crops of corn and soybeans, the literature reports ranges of loads per area of phosphorus
of 0.15 to 1.43 tons/mi2 and of nitrogen of 0.86 to 11.43 tons/mi2. Therefore, loads to the Gillespie Lakes are relatively
high for the given cropping practices, and application of best management practices may substantially reduce the per area
loads of these nutrients. Considering these loads and retention of sediment and nutrients, a review of basic lake management
practices is presented and discussed. This review is presented to assist lake managers in the achievement of lake water-quality
goals.
Citation
Title Water sediment, and nutrient budgets, and bathymetric survey of Old and New Gillespie Lakes, Macoupin County, Illinois, May
1996-April 1997; with a discussion of lake-management practices