Illinois Water Supply Planning


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Bloomington PWS - Water use and est. 40-yr drought yields
Bloomington PWS - Water use and est. 40-yr drought yields
Planning and reassessment are key to providing an uninterrupted, adequate supply of water to meet changing demands. Increasing populations and expanding networks create increasing demands on water supply sources. Community water supplies often expand services far beyond their corporate limits. While the demand for water is increasing, it is important for the supply to keep pace, particularly for reservoir-based systems, as impounding reservoirs lose storage capacity over time due to accumulation of sediment.


Bloomington PWS - Service area population projections  
Bloomington PWS - Service area population projections
The City of Bloomington offers an example of an expanding community supply system. The population of Bloomington and the number of persons in the total water supply service area have been increasing. At the same time, supply reservoirs have lost capacity, and the Bloomington public water supply has had to augment its water sources to keep pace with demand.


Rend Lake intercities water system - map
Rend Lake intercities water system (map)
Rend Lake offers an example of a regional water supply built to provide a reliable water supply for many communities and water districts in southern Illinois. It is the largest reservoir in Illinois built primarily for public water supply. Centralizing the treatment process has the added benefit of streamlining compliance testing.


Rend Lake intercities water system
Rend Lake intercities water system
Population projections and understanding water use trends are essential to successful long-term regional planning. During the planning for Rend Lake, population and per person water use were projected to forecast the water demand the reservoir was intended to meet. A comparison of population and water demand projections and reported values for Rend Lake shows that although the population served is greater than originally projected, per person water demand has not increased as predicted; thus, total water withdrawals are close to projected withdrawals.


Continuing reassessment of demand and supply throughout the state is critical to ensure adequate water in Illinois into the future.


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