East Branch Clarion River Lake, or East Branch Lake is a reservoir at Elk State Park in Elk County, Pennsylvania, in the United States. It was constructed by the U.S. Army Corps of Engineers by damming the East Branch of the Clarion River. Construction of the rolled earth, impervious core dam was authorized by the Flood Control Act of 1944. The lake is one of sixteen flood control projects administered by the Pittsburgh District of the Army Corps of Engineers. East Branch Clarion River Lake helps to provide flood protection for the Clarion River valley and the lower portions of the Allegheny River and the upper portions of the Ohio River.