Lake Decatur

Lake Decatur Watershed Map

History of the Lake Decatur Watershed Partnership

Sangamon River/Lake Decatur Watershed TMDL Report

For more information on how to get involved and get cost-share

Lake Decatur watershed encompasses 925 square miles in Macon, DeWitt, Piatt, McLean, Champaign, Ford, Shelby, Christian, and Sangamon Counties in central Illinois. 87% of the watershed is devoted to row crop agriculture. Cities and towns in the watershed include Decatur, Maroa, Cerro Gordo, Monticello, Mahomet, Gibson City, and Saybrook. Lake Decatur was built in 1922 and now serves the drinking water needs of 90,000 people. Almost immediately after it was built, however, sedimentation issues threatened to decrease the lake’s storage capacity, and by 1946 the planned storage capacity had been cut by 25%.

The Macon County Soil & Water Conservation District (SWCD) was formed in 1943 and by a year later, more than 200 farmers had been encouraged to use conservation practices such as contour farming, strip cropping, terracing, dams, and grassed waterways. Due to growing concern in the 1960s of the ecological effects of impounding natural streams, another reservoir project was put on hold. Over the years, dredging projects were conducted instead on Lake Decatur to increase the holding capacity of the lake. The various watershed committees and the Macon County SWCD have worked since then on encouraging conservation practices and the scientific application of fertilizer to ensure no more chemicals are used in the watershed than are needed.