Lower Illinois Regional Demands: Visualizing Water Use

How does water get used in the Lower Illinois Region?

The Illinois Water Inventory Program (IWIP) has been a core component of the Illinois State Water Survey (ISWS) since 1978. The Lower Illinois Region has five major water use sectors: public supply, domestic, industrial, agricultural, and environmental use (as seen in figure below).

The five major water use sectors in the Lower Illinois Region.

Surface Water Demands

In the Lower Illinois Region, there are four major sources of surface water for water supply: the Illinois River, Mississippi River, regional tributaries, and inland reservoirs. The total surface water withdrawals in the Lower Illinois Region were approximately 14 million gallons per day (mgd) in 2020. At present, all reported surface water withdrawals are used by either the environmental or public supply sectors. Environmental demands occur in the southwestern counties along the Illinois and Mississippi Rivers while public supply demands occur predominantly in Macoupin County with intakes on reservoirs and tributaries.

Surface water demands in 2020. Locations of withdrawals used for environmental supply are depicted in green, while those used for public supply are shown in brown. The size of each marker relates to the magnitude of withdrawals (i.e., larger circle equals larger volume of withdrawals).

Groundwater Demands

Aquifers are underground water sources that are naturally supplemented by rainfall, snowmelt, and other water that seeps into the soil. Many farmers use irrigation, which draws water from these groundwater aquifers. Reduced groundwater levels and, consequently, reduced crop yield potentially result from the aquifers' rapid depletion. Climate is a major driver of water use for agriculture with increased precipitation associated with decreased demands. The table below shows the relationship between annual precipitation and agricultural demands. For example, in the wet year 2015, water use for agriculture was approximately 5 mgd.

 1 Precipitation data were obtained from the Water and Atmospheric Resources Monitoring Program (WARM) network station at Perry, Illinois (WARM/ICN, 2015).

While some sectors consistently report to IWIP (public supply, industrial, environmental), other sectors have inconsistent reporting (agricultural) or are not required to report (domestic). Furthermore, these sectors often rely on different sources of water (e.g., groundwater, reservoirs, or streams) depending on their location in the region and the amount of water that they need to withdraw.

2020 Community supplies with the greatest groundwater demands in the Lower Illinois WSPR reported to IWIP. Details for the 2nd and 5th highest demands are not listed due to IWIP confidentiality. ‘NA’ means not available.

Estimated and IWIP reported values are shown in the figure below. Agriculture was estimated to be the largest water demand sector, followed by the public supply, and environmental sectors.

Reported and estimated 2020 water usage in the Lower Illinois Region


Funding Information

This story map is part of a series about Water Supply Planning throughout the state of Illinois. Water Supply Planning is an ongoing research effort conducted by the Illinois State Water Survey and is funded by the   Illinois Department of Natural Resources Office of Water Resources.  

The five major water use sectors in the Lower Illinois Region.

Surface water demands in 2020. Locations of withdrawals used for environmental supply are depicted in green, while those used for public supply are shown in brown. The size of each marker relates to the magnitude of withdrawals (i.e., larger circle equals larger volume of withdrawals).

 1 Precipitation data were obtained from the Water and Atmospheric Resources Monitoring Program (WARM) network station at Perry, Illinois (WARM/ICN, 2015).

2020 Community supplies with the greatest groundwater demands in the Lower Illinois WSPR reported to IWIP. Details for the 2nd and 5th highest demands are not listed due to IWIP confidentiality. ‘NA’ means not available.

Reported and estimated 2020 water usage in the Lower Illinois Region