Lake Oahe Lake Oahe Lake Oahe (oh-WAH'-hee) is a large reservoir behind Oahe Dam on the Missouri River; it begins in central South Dakota and continues north into North Dakota in the United States. The lake has an area of and a maximum depth of . By volume, it is the fourth-largest reservoir in the US. Lake Oahe has a length of approximately and has a shoreline of . 51 recreation areas are located along Lake Oahe, and 1.5 million people visit the reservoir every year. The lake is named for the 1874 Oahe Indian Mission. Lake Oahe begins just north of
Elwha Dam 20 years for the river to fully return to its pre-dam conditions. The ultimate goal of the dam removal is restoring the river to a nearly pristine state. Elwha Dam The Elwha Dam was a 108-ft (33 m) high dam located in the United States, in the state of Washington, on the Elwha River approximately upstream from the mouth of the river on the Strait of Juan de Fuca. The Elwha River Ecosystem and Fisheries Restoration Act of 1992 authorized the US Federal Government to acquire the Elwha Dam and Glines Canyon Dam hydroelectric power projects for decommissioning and demolition