Drought Vulnerability of Illinois' Community Surface Water Systems
The following contains an assessment of the potential impact of severe drought conditions on Illinois community water supplies, primarily based on the estimation of the water yield provided by each community’s surface water supply sources. Potential uncertainties in the estimation of each system’s yield have been analyzed to the extent where confidence limits are placed on yield values. The ISWS has designated that, to be considered adequate, a system should with 90% confidence be able to fulfill the community’s water demand through a severe drought similar to the historical drought of record. In contrast, previous ISWS yield studies for surface water supplies were characterized by a single estimate of the firm or safe yield, which essentially established roughly a 50% level of confidence. ISWS Contract Report 2007-08 provides a description of the various data uncertainties considered in determining the confidence of a yield estimate. Information describing the water sources of each surface-water supplied system was taken from ISWS Contract Report 2008-02 with selected updates. These studies were supported in part by funding from the Illinois Department of Natural Resources, Office of Water Resources.
Links with a community name (Altamont) will provide system information. The associated vulnerability link will provide that system's drought vulnerability classification.
Notes and Terminology