Water Quantity

Water is required to live, maintain health, and grow food.  We need enough water for drinking, agriculture, and commercial and industrial purposes.  In Illinois, climate change may increase the frequency and intensity of floods, droughts, and heat waves, all of which will negatively impact water supply. These climate change impacts and increased uncertainty about climate change threatens the water supply we need for human consumption, farming, recreation, and plant and animal habitats. 

Fortunately, future water quantity in Illinois is expected to remain stable under different climate change scenarios, according to An Assessment of Climate Impacts on Illinois, a study by the Nature Conservancy (74).  This means we are likely to have enough water to meet our needs, as long as our needs remain stable.  What happens when we get too much water? 

As Illinois’ population grows, so does our need for water. According to the IDNR study, Building Resiliency to Climate Change: A Call to Action, “Due to projected growth of the population and economy, Illinois could require 20 to 50% more water in coming decades” (13). In addition, more people are expected to move to the Great Lakes region to escape climate impacts in other areas of the country. This could put an even greater strain on our water systems.

The once-abundant water supplies of the Great Lakes and Illinois rivers may not be sufficient to sustain our growth, especially if climate change brings years of prolonged drought.

Impacts on future water supply will vary by region. For instance, Northeastern IL already consumes more water than it supplies. Scientists are concerned that climate change and future development could cause a water supply crisis in some Illinois regions. While our water supply is not as stressed as it is in the American West, we may find that we don’t have enough to meet the demand.   

Illinois’ most costly and frequently occurring natural disaster is flooding. Too much water all at once takes a huge toll on Illinois’ environment, economy, and communities (“Building Resiliency to Climate Change” 23). The high stream flows associated with frequent or intense rainfall can cause damage by scouring the channel bottom or banks, lead to excessive sedimentation as the flood event subsides, or displace organisms. It disrupts navigation along roads, rivers, and reservoirs and causes damage to urban areas and agricultural lands (Pryor et al. 80). Despite better floodplain mapping, stringent regulations, and proactive flood mitigation programs, the number of structures damaged and the costs for repairs due to climate change continue to increase in Illinois (“Building Resiliency to Climate Change” 23).

The Office of Water Resources at IDNR is the leading state agency for water resources planning with respect to quantity. OWR manages navigation, floodplain management, the National Flood Insurance Program, water supply, drought, and interstate organizations on water resources.  Climate change will impact flooding so additional floodplain management and flood control needs are expected to grow.  Similarly, climate change could also reduce overall availability of water in certain regions in the state so water supply levels will continue to be monitored.  

Some existing programs and efforts at IDNR assist in monitoring flooding and droughts for use by planners, responders, and communities:

• Flood Surveillance Program
• Flood Inundation Mapping
• Drought Preparedness and Response Plan
• IL State Water Plan
• Floodplain Regulatory Program
• Lake Michigan Allocation Program
• Illinois Water Inventory Program
• Regional Water Supply Planning Committees implementation
• Flood Mitigation Program

These programs currently exist within IDNR to assist with water resources issues for communities throughout the state. These programs will need to continue, but they will also need to adapt to meet the changes imposed by climate change.  

IDNR Office of Water Resources
This webpage provides information about IDNR’s Office of Water programs. It provides access to a variety of helpful water resources, including flood maps, flood preparedness, water permitting, and more.

IDNR Office of Water Resources: Water Supply
This webpage provides information about IDNR’s work to ensure that there is an adequate and reliable supply of clean water for all Illinois residents. It includes information about permits, planning, and the Lake Michigan Water Allocation Program.

IDNR Office of Water Resources: Division of Water Resource Management
This webpage provides information about regulatory programs for floodway construction activities, public waters, construction, maintenance of dams, and more.

Illinois State Water Survey: Building Resiliency to Climate Change
This report, funded by IDNR and produced by the Prairie Research Institute, describes the extreme weather events that are likely to intensify due to climate change. It offers recommendations for how Illinois can build resilience to these climate change impacts, focusing on Illinois water systems.