Countywide forecasts of water use available for Illinois, Midwest

Water use in Illinois is expected to grow faster than the population in the next 20 years, with Chicago-area counties leading increased demand in 89 of the state’s 102 counties, according to two new studies released by the Illinois State Water Survey.

“These studies project county-level water use for Illinois and five other states in the Midwest, information that is critical if we are to ensure that we have adequate and safe supplies of this life-sustaining element in the future,” said ISWS Chief Derek Winstanley, an adjunct professor of geography at the University of Illinois at Urbana-Champaign.

Ben Dziegielewski, a professor in the department of geography and environmental resources at Southern Illinois University in Carbondale, is lead author of both reports: “County-Level Forecast of Water Use in Illinois: 2005–2025” and “Countywide Projections of Community Water Supply Needs in the Midwest.”

The first report includes estimates of future water use in Illinois counties based on the best available data and forecasting methods. The result is a set of water-demand forecasts for seven water-use sectors in Illinois: thermoelectric, public supplies, self-supplied commercial and industrial usage, irrigation, mining and livestock.

Water use is expected to grow faster than the state’s population, which is projected to increase by 1.5 million over the next 20 years,” Dziegielewski said. “Projected water use increases from 1,302 gallons per capita per day in 2000 to 1,487 per capita per day in 2025, primarily due to projected increases in the thermoelectric sector.”

By 2025, almost 17 billion gallons of water per day will be needed for generating electricity in Illinois, he said. That amount, Winstanley said, will be about eight times greater than the amount of water diverted from Lake Michigan. “Some 97 percent of the water needed to produce energy is recycled, but up to 3 percent is consumed,” he said. “This means that by 2025 up to 500 million gallons of water per day will be consumed to generate electricity for Illinois, the Midwest and the nation.”

Total water use is projected to increase in 89 of the 102 counties in Illinois. Public water supplies often are of most concern to planning agencies, and that usage is projected to increase from 164 gallons per person per day in 2000 to 181 gallons per person in 2025. “Some of the projections could be reduced by implementing water-conservation programs and improving efficiency of water use,” Winstanley said.

The thirsty spot in the state is the Chicago metropolitan area. “Public-supply-water use is projected to increase by an average of about 30 percent in Cook, DuPage, Will, Lake, and Kane counties, requiring an additional 450 million gallons per day,” Winstanley said.

The forecasts should provide a benchmark for use in regional water-supply studies, Dziegielewski said. “Regional or local planners could allocate county-level projections into smaller areas (townships and cities) by pro-rating county totals based on population, employment, or other demand drives in each sector. These forecasting methods also could be used to project water use based on locally available data sources.” Planners also need to be prepared for periods of drought, when water supply diminishes and water demand increases, Winstanley added.

The second report analyzes the region’s public-supply water use, covering Illinois, Indiana, Michigan, Minnesota, Ohio and Wisconsin. It gives useful insights about the relationship between water use and factors most likely to predict or explain water use, Dziegielewski said. It also offers perspective on the challenges facing water-system managers and regional officials in planning to meet future water-system infrastructure needs in the region.

The regional report, available at mtac.sws.uiuc.edu, also reviews water-use projections and related findings of the study, and recommends actions that may improve water-use forecasting and infrastructure planning for drinking water systems.

Project sponsors for the Illinois study were the Illinois State Water Survey and the SIU-Carbondale department of geography and environmental resources, with funding from the Illinois Board of Higher Education. Sponsors for the regional report were the U.S. Environmental Protection Agency’s Midwest Technology Assistance Center, housed at both the ISWS and SIU.