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New water demand forecast highlights need for sustainable water management

Clean, reliable, and affordable water is vital for northeastern Illinois’ health and prosperity. But many areas of the region, especially those dependent on groundwater (water found underground in the cracks and spaces in soil, sand and rock), are already encountering issues with water supply and quality.

Understanding future water demand is key to managing these resources sustainably. The Chicago Metropolitan Agency for Planning (CMAP), Illinois-Indiana Sea Grant (IISG), and University of Illinois Extension recently updated the region’s water demand forecast to reflect new population and employment projections. The forecast shows that water use is expected to continue declining, due to steady advances in water conservation and efficiency that are outpacing population and employment growth. However, in some areas, forecasted water demand will exceed available groundwater supplies.

Municipal water systems are the largest users, withdrawing 90 percent of all water in the seven-county region in service of 7.89 million people and corresponding businesses and institutions. Actions taken today can help preserve a sustainable water supply for future generations.

This forecast estimates future water demand to the year 2050 at the municipal, county, and regional level, as well as by water source and sector for the seven-county region. It can help local and regional planners understand the sufficiency of water sources and take actions to conserve water, protect supplies, and explore alternative drinking water sources — strategies highlighted in ON TO 2050, the region’s comprehensive plan.

Regional trends in water demand

By 2050, northeastern Illinois is projected to add more than 1.4 million residents and nearly 300,000 jobs. Despite this growth, total water demand is projected to decline. Total water withdrawals are estimated to reach 938 million gallons per day (MGD), an 8 percent decrease from 2018 levels.

Figure 1. 2024 regional water demand forecast and 2022 socioeconomic forecast

The projected decline in water use reflects ongoing improvements in water conservation and efficiency, such as: 

• Installation of water-efficient plumbing fixtures and appliances
• More compact and infill development patterns
• Industrial innovation and technological improvements
• Infrastructure maintenance to reduce water loss

Maintaining a sustainable water supply still has its challenges

While declining water demand is a positive trend, there are still challenges. Since 2007, the region has reduced water demand by 17.4 percent, but further reductions are needed to ensure a sustainable water supply for the future.

The Illinois State Water Survey developed sustainable supply values for each water source in the state. For groundwater, these values estimate the annual amount of water that can be pumped without causing further desaturation of deep aquifers or harming aquatic ecosystems due to reduced groundwater discharges to streams. At the county level, this data allows the regional water demand forecast to identify areas where water demand is expected to exceed available sustainable supplies of water over the long term.

CMAP calculated demand-to-sustainable supply ratios for shallow and sandstone groundwater sources (Figures 2 and 3), and the extent to which water demand is expected to exceed sustainable supply by 2050. Ratios greater than one mean that demand surpasses the estimates.

Figure 2. Demand-to-sustainable supply ratio for shallow groundwater, 2050

Figure 3. Demand-to-sustainable supply ratio for sandstone groundwater, 2050

While the sustainable supply estimates will continue to advance and incorporate water quality, drought, and other seasonality issues, the demand-to-sustainable supply ratios give the region insights into the scale of action needed to maintain a long-term supply. Figure 4 estimates how much demand should be reduced in each county so that total demands remain within sustainable supply estimates. Further study could help illuminate where reductions are needed most within a county and identify water quality or seasonality constraints that could further refine these values.

Figure 4. Demand reduction needed to align with shallow and sandstone sustainable supply estimates by county, 2050

County	Reduction needed (MGD)
Cook	0.54
DuPage	2.44
Kane	12.59
Kendall	N/A
Lake	0.11
McHenry	N/A
Will	4.02
Total	19.71

For example, Kane County’s water demand already exceeds its available supply as of 2018, an imbalance which is expected to worsen by 2050. And even for those counties where overall demand appears sustainable, the risk of localized challenges due to concentrated demand or unique geologic conditions exist in parts of Kane, Kendall, McHenry, and Will counties.  

Water quality concerns further complicate the picture, adding a layer of uncertainty not reflected in demand-to-supply ratios. In some areas, even where water supplies seem abundant, poor water quality can make the resource effectively unusable due to the high costs of treatment.   

Furthermore, demand estimates are subject to change. Factors such as in influx of high water use industries like data centers, higher than expected population and employment growth, or a decline in conservation and efficiency practices could drive future water use higher. Conversely, water use could reduce faster than expected through advancements in technology, increased water reuse, expanded conservation practices, or slower population and employment growth. Other uncertainties and data limitations are explored in more detail in the forecast. 

Supporting sustainable water management  

Ensuring a long-term water supply requires reducing demand in key areas, aligning use within the limits of available supplies, and protecting water quality. For the first time, the demand-to-sustainable supply ratios provide the region with valuable insights for where to increase conservation and efficiency efforts and where identifying alternative water sources may be necessary. 

Many communities have taken steps to secure alternative water sources. Notably, communities in Kendall and Will counties are planning to access Lake Michigan water in 2030 and 2035, source switches that are accounted for in this forecast (Figure 5). Additional communities may conclude that alternative sources are necessary based on local assessments, which could change the demand-to-supply ratios. 

Figure 5. Water source by forecasted municipality, based on average source mix from 2013-2018

Next steps 

The regional water demand forecast update informs current work underway to coordinate and conserve our shared water supply resources. 

Collaborative planning  

CMAP is working with the Northwest Water Planning Alliance — a coalition of 3 counties and 5 councils of government representing over 80 communities — to create a Water Supply Sustainability Plan. This plan will provide a roadmap for voluntary steps that communities can take to support long-term sustainable use of water resources. 

Developing a more robust legal framework 

Despite voluntary conservation actions being taken by individual jurisdictions, the region’s sandstone aquifers face desaturation due to decades of withdrawals that exceed their natural recharge rates. Illinois’ current legal framework, established by the Water Use Act of 1983, fails to address these challenges, putting community water supplies at risk.  

CMAP recently published Securing Illinois’ Groundwater Future, which examines the state’s 1983 Water Use Act and draws insights from groundwater governance practices in neighboring states. The report outlines several recommendations to modernize Illinois’ groundwater management framework, ensuring a balance between economic growth and the stewardship of vital water resources. 

Informing decisions with data 

The updated water demand forecast and supporting data enable counties, municipalities, water utilities, and residents to have informed discussions about supply and demand challenges and make data-driven decisions — the Illinois State Water Survey uses this data to inform its own water supply conditions modeling. The CMAP DataHub provides access to regional, county, and sector demand forecasts, reported water withdrawals, and data on current and projected population and employment.