Dworshak Dam is a concrete gravity dam in the western United States, on the North Fork of the Clearwater River in north central Idaho. In Clearwater County, the dam is located approximately four miles northwest of Orofino and impounds the Dworshak Reservoir for flood control and hydroelectricity generation. By capacity, the reservoir is the largest i…Dworshak Dam is a concrete gravity dam in the western United States, on the North Fork of the Clearwater River in north central Idaho. In Clearwater County, the dam is located approximately four miles northwest of Orofino and impounds the Dworshak Reservoir for flood control and hydroelectricity generation. By capacity, the reservoir is the largest in Idaho and fourth-largest in the Pacific Northwest.