Water Supply Planning for Illinois

Rachel M. Gregg Jessica Hitt
Posted on: 9/18/2013 - Updated on: 3/02/2020

Posted by

Rachel Gregg

Project Summary

The Illinois State Water Survey, in collaboration with the Illinois Department of Natural Resources’ Office of Water Resources and the Illinois State Geological Survey, examined historical climate information and future climate scenarios in order to improve the understanding of and planning for the effects of climate change on supply and demand of regional water resources. The project examined climate impacts (e.g., temperature, precipitation) on surface and groundwater resources and resulting complications for sustainable water supply planning in the state.


Approximately 16 billion gallons of water are used every day in Illinois; about 85% is used for domestic electric power production, most of which is recycled. The remaining 15% (~2 billion gallons) is withdrawn and consumed by state residents. The water supply/demand issue is prevalent in the state with an ever-expanding population and increasing demand for water. Planners and managers must deal with a variety of challenges, including the quality, availability, and demand of water and how these are affected by events such as droughts, flooding, and climate change. Climate impacts of concern to water resources in the state include changes in temperature and precipitation patterns, which can cause secondary effects on water supply and demand.

In 2006, former Governor Rod Blagojevich issued Executive Order 2006-01 requiring the state to develop and implement regional water supply plans. Through a three-year funded program, the Illinois State Water Survey worked with partners to pilot water supply planning in two regions – East Central Illinois and Northeastern Illinois. The program’s goals were to assess water resource availability and to evaluate the impacts of climate change on the ability to meet future water demands. Project staff examined water availability, demand, and cost under projected population changes and different climate scenarios.


The project began by looking at two priority watershed regions: Northeastern Illinois and East Central Illinois. The focus in Northeastern Illinois was on the Fox River watershed and the Deep Bed aquifer system. The focus in East Central Illinois was on the Mahomet aquifer system and the Sangamon River watershed. The primary program partners – the Illinois State Water Survey, Illinois State Geological Survey, and the Illinois Department of Natural Resources’ Office of Water Resources – collaborated to provide technical support to the two regional planning groups and developed models to support the evaluation of water management strategies to meet changing water resources needs through 2050.

Planning groups were formed and led by different entities in the pilot regions. In the Northeastern Illinois pilot area, the Chicago Metropolitan Agency for Planning led the Regional Water Supply Planning Group (RWSPG) (Meyer et al. 2012); in the East Central Illinois pilot area, the Mahomet Aquifer Consortium led the Regional Water Supply Planning Committee (RWSPC) (Roadcap et al. 2011). Both the RWSPG and the RWSPC were responsible for developing water supply planning and management guidelines with support from the primary program partners. The partners worked to examine and understand water supply and demand over a 50-year time period in order to develop materials to support decision making, planning, and management of water resources in changing socioeconomic and climatic conditions. They examined water withdrawals and uses, assessed future temperature and precipitation conditions for Illinois using publicly available GCMs, incorporated those conditions into surface water and groundwater models for the regions, and evaluated needed changes to existing water resources policies and regulations, following the Illinois State Water Survey’s framework (Winstanley et al. 2006).

Outcomes and Conclusions

Through this program staff were able to analyze the state’s water supply systems and projected climate change impacts and provide recommendations to improve resilience. Key steps to support sustainable water supply planning were identified, such as evaluating existing facilities to cope with drought conditions and building historic drought and climatic data into water supply scenarios to enhance the resilience of infrastructure. Before the project was initiated, state water planning activities were often fragmented; this effort aimed to increase dialogue and coordination, and allowed managers to look at the cumulative impacts of use and management response strategies on water resources.

Regional planning is currently underway in three Priority Water Quantity Planning Areas – East Central Illinois, Northeastern Illinois, and the Kaskaskia Region in southwestern Illinois. The RWSPG and the RWSPC groups continue to work to coordinate community and stakeholder involvement to achieve water supply sustainability.


Gregg, R. M. & Hitt, J. L. (2012). Water Supply Planning for Illinois [Case study on a project of the Illinois State Water Survey]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: www.cakex.org/case-studies/water-supply-planning-illinois (Last updated October 2012)

Project Contact

H. Allen Wehrmann
[email protected]

Affiliated Organizations

The Illinois State Water Survey (ISWS) is a Division of the Prairie Research Institute of the University of Illinois at Urbana-Champaign (U of I). The Water Survey has flourished for more than a century by anticipating and responding to new challenges and opportunities to serve the citizens of Illinois. Today, the ISWS continues to demonstrate flexibility and adaptability by developing new programs, while continuing to provide long-standing services upon which Illinoisans have come to rely.