Drought Vulnerability of Illinois' Community Surface Water Systems - Vulnerability, Illinois State Water Survey

Illinois Drought


Drought Vulnerability Classification

Inadequate System – There is greater than a 50% probability that the current system would not be able to provide the community’s current rate of water demand through a severe drought similar to the drought of record.

Drought Adequacy Description

If a drought similar to the 1953-1954 drought of record were to recur today, it is estimated with 50% confidence that the current system would be able to support a demand of 27.8 mgd (the mid- or best yield estimate). It is estimated with 90% confidence that the current system would be able to support a demand of 25.7 mgd. Because the system would not be able to fulfill the community’s current demand of 32.0 mgd with 50% confidence, the drought vulnerability of the system is classified as INADEQUATE.

Additional Notes

Note that this assessment is based on the total water demand which includes water used for both community supply and that needed for operation of CWLP’s coal-fired electricity-generating plants. The water budget analysis used in this assessment indicates that most of the electricity-generating plants would need to cease operations during a severe drought condition when Lake Springfield’s level falls below 548 feet. It is unlikely (less than a 10% probability) that the potable community supply would be depleted under hydrologic and climatic conditions similar to the 1953-1954 drought of record. However, even if the assessment of drought vulnerability were based solely on the potable supply, the Springfield system would be classified as MARGINAL.

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Illinois State Water Survey

2204 Griffith Dr., MC-674
Champaign, IL 61820-7463
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