The Missouri River and Hauser Lake. That is Canyon Ferry Dam down there.

Canyon Ferry Dam is a concrete gravity dam in a narrow valley of the Missouri River, United States, where the Big Belt Mountains and the Spokane Hills merge, approximately 68 miles (109 km) downstream from the confluence of the Gallatin, Madison, and Jefferson rivers, and about 20 miles (32 km) east of the city of Helena, Montana. The dam is for flood control, irrigation, recreation and hydroelectric power. The building of the dam created a reservoir known as Canyon Ferry Lake