Lake Decatur is a 2,800-acre (11 km²) reservoir located in the city of Decatur, Illinois, east of downtown. The city and lake both share the name of U.S. Navy Commodore Stephen Decatur. The lake is 613 feet (187 m) above sea level. Lake Decatur has a watershed of 925 square miles (2,396 km² or 592,000 acres) spanning 7 counties.