There are over 1,000 reservoirs throughout Illinois, of all sizes. Here are the biggest in the state including the largest man-made lake in Illinois.

Most Common Reasons for Building a Reservoir

The U.S. Army Corps of Engineers builds reservoirs for various reasons, but some of the most common reasons include:

Flood Control

Reservoirs are often constructed to mitigate the risk of flooding in downstream areas by storing excess water during heavy rainfall and releasing it in a controlled manner.

Water Supply

Reservoirs serve as a reliable source of water supply for domestic, agricultural, industrial, and municipal purposes. They store water during wet periods for use during dry periods.

Hydropower Generation

Reservoirs are utilized to generate hydropower by controlling the flow of water through turbines, thus converting the energy of flowing or falling water into electricity.

Environmental Management

Reservoirs can be designed to improve water quality, preserve aquatic habitats, and manage ecosystems. They may also provide opportunities for wetland restoration and wildlife conservation.

Recreation

Reservoirs often offer recreational opportunities such as boating, fishing, swimming, and camping, contributing to tourism and local economies.

These are some of the primary reasons why the Army Corps of Engineers may build reservoirs, although the specific purposes can vary depending on the project's location, environmental considerations, and local needs.

MORE: The Cleanest Lake in Illinois


 

5 Biggest Reservoirs in the State of Illinois

Clinton Lake

Clinton Lake Bailey Aerial Video via YouTube
Clinton Lake Bailey Aerial Video via YouTube
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Clinton Lake is a 4,900-acre/7.6 square-mile reservoir located near Clinton, Illinois. The lake is a part of the Clinton Lake State Recreation Area, which encompasses 9,300 acres. It was built in the 1970s as a cooling source for the Clinton Nuclear Generating Station.


 

Crab Orchard Lake

The Traveler via YouTube
The Traveler via YouTube
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Crab Orchard Lake is a 6,965-acre/10.8 square-mile reservoir in Williamson County, Illinois. It is the centerpiece of the Crab Orchard National Wildlife Refuge.


 

Rend Lake

Rend Lake Droning USA via YouTube
Rend Lake Droning USA via YouTube
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Rend Lake is a 13-mile long, 3-mile wide reservoir located in Southern Illinois in Franklin and Jefferson Counties near the town of Benton. It contains 18,900 acres of water, stores 185,000 acre-feet of water, and supplies over 15 million gallons of water per day to 300,000 persons in over 60 communities.


 

Lake Shelbyville

Lake Shelbyville via Facebook
Lake Shelbyville via Facebook
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Lake Shelbyville is a reservoir located in Shelby County, Illinois, and Moultrie County, Illinois created by damming the Kaskaskia River at Shelbyville, Illinois. The lake's normal surface pool is 11,100 acres/17.3 miles.


 

Carlyle Lake

Carlyle Lake via Facebook
Carlyle Lake via Facebook
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Located on the Kaskaskia River, Carlyle Lake is the largest man-made lake in Illinois. Formed in 1967, the lake encompasses an area of around 26,000 acres or 40.6 square miles. This makes Carlyle Lake not only the largest man-made lake in Illinois but also the largest overall lake in the state.

Carlyle Lake primarily serves as a water storage facility for flood risk management. However, it also serves as a popular recreation area and supports wildlife conservation as well as water quality and supply operations.

The lake is also one of Illinois’s top fishing and hunting locations.

Carlyle Lake is located in southern Illinois, about 50 miles east of St. Louis, Missouri.

MORE: 5 of the Best Camping Lakes in Illinois

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