Lake Monroe is owned by the US Army Corps of Engineers and managed by the Indiana Department of Natural Resources. Lake Monroe (also known as Monroe Reservoir) is the largest man made body of water in Indiana at 10,750 acres. The watershed drainage area for Lake Monroe is 441 square miles and discharges into Salt Creek. The watershed sits in five counties including Monroe, Brown, Lawrence, Jackson and Bartholomew.

The Lake was built in 1964 and filled with water in 1965 by the Louisville District of the Army Corps of Engineers and designed originally for flood control for the White River. The Lake is 538 feet above sea level and is 35-40 feet deep. The spillway is 556 feet above sea level.

The City of Bloomington began to use Lake Monroe as a drinking water source in 1967. At that time, the City also relied on Lake Griffy as a drinking water source. However, in 1996, the City of Bloomington Utilities Department deactivated the Griffy plant and began to rely on Lake Monroe. The Monroe Water Treatment Plant currently averages pumping 15 million gallons per day (MGD). This number has been as high as 23 MGD in warmer months. The Monroe Water Treatment Plant is a conventional rapid sand filtration plant.

Besides flood control and drinking water supply, Lake Monroe is used for recreational purposes. The lake draws people from all over the state each year for fishing, camping, hiking and several other recreational activities.