Lake Decatur is a reservoir located in the city of Decatur, Illinois, USA, east of downtown. The city and lake both share the name of U.S. Navy Commodore Stephen Decatur. The lake is above sea level and has a watershed of or reaching into parts of seven counties. The largest lake on the Sangamon River, it was created in 1920–1922. History The lake was constructed as a source of water for Decatur, especially the local corn refining industry. The corn refiner A.E. Staley led the campaign to persuade Decatur to borrow the $2.0 million necessary for the project. Staley was not being altruistic; corn wet-milling, which Staley's successor firm, Tate & Lyle, and its local competitor, Archer Daniels Midland, carry on to this day, is a water-intensive industrial process. Lake Decatur water is also used in the process of refining corn into ethanol. In 2007, about 76 percent of Lake Decatur's water was used for commercial and industrial purposes. As the largest artificial lake in Illinois at the time of construction, with a shoreline, Lake Decatur became a focus of Mid-Illinois recreation. The invention of the gasoline-powered speedboat had made sheltered reservoir waters attractive to many inland Americans. Today In the years since its completion in 1922, the aging Lake Decatur has suffered from extensive siltation problems. It was designed to sit atop relatively flat prairie land and is vulnerable to deposits of silt eroded from farm fields in the upper Sangamon River drainage area. From 1923 to 1983, Lake Decatur lost an estimated 35% of its designed storage volume. Although this trend has since been slowed by ongoing dredging, in 2004, Lake Decatur was described as having an average depth of only . 2008 rainfall replenished lake levels although the dredging operations have failed to stem the loss of reservoir storage capacity. City officials considered, but ultimately decided against, constructing a second reservoir for water storage purposes. In 2018, The City of Decatur completed a four-year long, $91 million dredging effort that increased the storage capacity of the lake by 30%. Lake Decatur borders two of Decatur's largest parks, Faries Park and Nelson Park, as well as Scovill Zoo. The Decatur Park District was founded in 1924 to take advantage of the opportunities arising from the creation of the lake. Lake Decatur can be seen from U.S. Highway 36, which crosses the lake on a causeway bridge located on