The Northwestern Division, and its Districts operate within all of the United States portion of the Columbia River Basin and coastal river basins in Oregon and Washington and the Missouri River Basin.
The Columbia River is the fourth largest river in North America. The geographic and hydrologic characteristics of the river, which drains a 259,000 square mile basin, are ideally suited to beneficial multiple-purpose storage development. Since the 1930s, numerous dams, both Federal and private, have been built to store water for flood control, to generate hydroelectric power, and for other purposes. Total storage capacity of these dams is about 25 percent of the 156 million acre foot average annual runoff volume for the Columbia River at its mouth. Federal projects in the basin have 19,900 megawatts of existing hydroelectric capacity, and non-federal projects add 10,700 megawatts.
The Missouri River is the longest river in the United States extending 2,619 miles from its source at Hell Roaring Creek and 2,321 miles from Three Forks, Mont. where the Jefferson, Madison and Gallatin Rivers converge in southwestern Montana, near the town of Three Forks. The Missouri River flows generally east and south about 2,321 miles to join the Mississippi River just upstream from St. Louis, Mo. The Missouri River basin has a total drainage area of 529,350 square miles, including about 9,700 square miles in Canada. That part within the United States includes all of Nebraska; most of Montana, Wyoming, North Dakota and South Dakota; about half of Kansas and Missouri; and smaller parts of Iowa, Colorado, and Minnesota.
There are six Missouri River Mainstem Reservoir System dams: Fort Peck, Garrison, Oahe, Big Bend, Fort Randall and Gavins Point. These six Corps reservoirs contain about 73.4 million acre-feet of storage capacity and comprise the largest reservoir system in the United States. It contains 71 percent of the installed capacity in the basin’s Federal hydroelectric power system, provides almost all of the reservoir support for downstream flow support on the Missouri River and contributes greatly to flood risk reduction for over 2 million acres of land in the floodplain of the Missouri River. At normal pool levels, these reservoirs provide an aggregate water surface area of 1 million acres for recreation and fish and wildlife enhancement.
Other major project purposes are fish and wildlife, navigation, municipal and industrial water supply, irrigation, and recreation.
The North Pacific Region and Missouri River Water Management Divisions play a key role in developing and operating the complex system of multiple-purpose projects. This role involves hydrologic investigations, power system analyses, flood risk reduction studies, project economic studies, operational planning, seasonal, and day-to-day project control.