The Pymatuning Reservoir in Crawford County, in the US state of Pennsylvania, was once a very large swamp. The Shenango River flowed through this ancient swamp and provided sustenance to industries located downstream in the Beaver and Shenango valleys. But when a devastating flood hit the valleys in 1913, the need to tame the river was felt.

In 1934, a dam and a reservoir was built to conserve waters entering the swamp and to regulate the flow of water in the Shenango and Beaver rivers. A concrete spillway bowl was also built to allow independent regulation of the upper reservoir. The flow of water over the bowl brings a constant supply of natural food into the area, including plant material, insect larvae, crayfish and other invertebrates, drawing a large number of fish to this structure. As soon as this phenomenon was discovered, the Linesville spillway became an impromptu tourists attraction.

Photo credit: Frankmiklos/Panoramio