Lake Decatur is the water supply reservoir for the city of Decatur. The reservoir was created in 1922 by construction of a dam to impound the flow of the Sangamon River. The dam created a lake with a volume of 20,000 acre-feet, but was later modified in 1956 to increase the maximum capacity of the lake to 28,000 acre-feet. The drainage area of the Sangamon River upstream of Lake Decatur is 925 square miles.published or submitted for publicationis peer reviewe
