Alum Creek State Park is a 4,630-acre Ohio state park in Delaware County, Ohio, in the United States. Alum Creek Lake was constructed from 1970 to 1974 as part of the Flood Control Act of 1962. Alum Creek Dam was constructed on Alum Creek, a tributary of Big Walnut Creek, which drains into the Scioto River. Alum Creek Reservoir holds 3,387 acres of water and is open to fishing, boating, ice fishing, ice boating, and swimming.