Study Identifies Cities Where Water Shortages May be a Future Issue in East-Central Illinois, Illinois State Water Survey

ISWS Press Release

For Immediate Release February 14, 2012
Study Identifies Cities Where Water Shortages May be a Future Issue in East-Central Illinois
George Roadcap - (217) 333-7951,
Listen to a podcast of an interview with Vern Knapp and George Roadcap on WILL radio:

Groundwater is plentiful for water supplies in future years, but surface water may be lacking, especially for Springfield, putting East-Central Illinois communities at risk for water shortages in a serious drought, according to George Roadcap, Hydrogeologist with the Illinois State Water Survey (ISWS) in the Prairie Research Institute at the University of Illinois at Urbana-Champaign.

Aerial view of Lake Decatur

In an East-Central Illinois study of the Mahomet Aquifer and four large surface water supply reservoirs, one each in Bloomington, Danville, Decatur, and Springfield, scientists used computerized water models and data to determine how current and future water use will affect the aquifer and streams, lakes, and rivers in the area up to the year 2050. Future water demands were evaluated under a baseline scenario, a more resource intensive scenario in which no water conservation measures are used, and a less resource intensive scenario.

Results showed that none of the current groundwater users of groundwater could be considered “at risk” for a future water shortage under all three scenarios.

Surface waters, such as lakes, rivers, and streams, are typically replenished whenever it rains, but their availability for water supply may be greatly restricted in an extended drought.

“On the groundwater side, there were no new concerns; there is actually more groundwater in the Mahomet Aquifer than we previously stated,” said Roadcap.  “The key is that streams lose most of their water to the aquifer under high steam flow conditions.”

In the study, drought vulnerability was classified based on the estimated probability that the community supplies in water reservoirs could experience water shortages in an extreme drought.  Springfield is considered an inadequate system because there is greater than a 50 percent probability that a water shortage would occur.

Illinois soybean irrigation in action

The situation is less dire for Bloomington and Decatur, which are considered “at-risk” systems with greater than a 10 percent probability of shortage.  Danville is considered an adequate system, but with projected growth in demand, the supply is expected to become at-risk by 2040.

These results and future predictions can be used in water supply management and planning, Roadcap said.  The communities involved in the study that use surface water are actively considering adding groundwater sources to their water systems. In some cases, using groundwater to meet water needs of the community may be expensive, and costs must be considered in water supply management.

The study was initiated in 2006 and is ongoing to determine how the Mahomet Aquifer responds to droughts and floods.   A grassroots water supply planning group, the East-Central Illinois Regional Water Supply Planning Committee, was formed to develop planning recommendations in accordance with existing laws.  The Illinois State Water Survey provided technical support and updated the regional water resource information.

Study results are summarized in a report that is available on the Illinois State Water Survey website at

For more information, contact the ISWS Center for Groundwater Science at (217) 333-6800.

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