. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. STREAMFLOW CONDITIONS. FLOODING. AND LOW FLOWS 1000 100. 10- 1915 1925 1935 1945 1955 1965 1975 1985 1995 Figure 13. Annual 7-day low-flow series of the Fox River at Algonquin. Increases since the 1940s are caused by changes in reservoir operation from the Fox Chain of Lakes. operation policy, rather than from any inherent dam characteristics. The gage records from all the other reservoirs demonstra
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. STREAMFLOW CONDITIONS. FLOODING. AND LOW FLOWS 1000 100. 10- 1915 1925 1935 1945 1955 1965 1975 1985 1995 Figure 13. Annual 7-day low-flow series of the Fox River at Algonquin. Increases since the 1940s are caused by changes in reservoir operation from the Fox Chain of Lakes. operation policy, rather than from any inherent dam characteristics. The gage records from all the other reservoirs demonstrate an increase in low flows after dam construction, all as a result of protected flow releases from the reservoir. Trends in low flows on these streams are therefore subject to changes in policy, as compared to a physical cause-and-effect relation- ship. The low-flow increases on the Salt Creek near Rowell and the Kaskaskia River gages is moderate, <10 cfs. The gages on the Big Muddy River show substantial increases in low flows, shown in figure 14. High Flows. Lakes Shelbyville and Carlyle, located on the Kaskaskia River, and Rend Lake on the Big Muddy River were all built primarily for flood control. The three gages directly downstream of these reservoirs (at Shelbyville, Carlyle, and Plumfield) all show signifi- cant reductions in flood flows, as illustrated for Lake Carlyle in figure 15. Two gages, at Vandalia and Murphysboro, are located approximately 50 miles downstream of Lake Shelbyville and Rend Lake, respectively. Both of the gages show only slight reductions in flooding, below a level that is detected by the Kendall analysis. In a similar manner, the Rowell gage, located 13 miles downstream of Clinton Lake, shows only a small reduction in flooding. Lake Decatur and the Fox Chain of Lakes, upstream of the Decatur and Algonquin gages, respectively, are not designed to provide much reduction in flooding and therefore show no trend. Seasonal Flow. Reservoirs do not or
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