The U.S. Army Corps of Engineers is the single largest owner and operator of hydropower in the U.S., with 24 percent of the nation's hydropower generating capacity. The percentage is 16 percent for the Bureau of Reclamation and 6 percent for the Tennessee Valley Authority. Corps dams have a total nameplate capacity of close to 21,000 Megawatts (MW) and produce an average of almost 100 Billion Kilowatt-hours (KWh) of energy annually. Non-federal power plants at Corps facilities add about another 2,000 MW of capacity.
Most of the Corps hydropower production is in the Northwestern Division (75.2 percent), including 62.6 percent in the North Pacific Region (NPR) and 12.6 percent in the Missouri River Region. The percentage for other divisions is 10.9 percent for South Atlantic Division, 8.3 percent for Southwestern Division, 4.4 percent for Lakes and Ohio River Division, and 1.1 percent for Lower Mississippi River Division.
The total plant capacity of Corps dams in the Pacific Northwest is 14,524 MW -- 43 percent in Portland District, 35 percent in Walla Walla District, and 22 percent in Seattle District.
In most years, most of the electricity used in the Northwest come from hydropower dams (53 percent), followed by power plants that use coal (33 percent), natural gas and oil (8 percent), nuclear energy (3 percent) and a combination of other resources (3 percent). Typical cost range of new power sources (in cents per kilowatt-hour) varies as follows: natural gas (2.9 to 9), new small hydro (4.3), wind (5.3), geothermal (5.7), solar energy (18 to 39).
Walla Walla District
The Walla Walla District operates and maintains six hydropower facilities at Ice Harbor, Little Goose, McNary, Lower Monumental, Lower Granite and Dworshak dams. They provide a clean, reliable, renewable, efficient, flexible power source that helps reduce the region’s carbon emissions footprint.
These facilities are capable of producing 4,400 megawatts of energy, enough to power a city the size of Seattle. Annual production equals about 15 billion kilowatts, which equates to about $895 million. Kaplan Turbines are the main workhorse of the District. They are approximately 90 percent to 95 percent efficient and have adjustable blades allowing operators to tilt them in response to changing water conditions. While they are a little more complex than other turbines, they turn at only 87.5 rpm and are designed to have a long service life.
Walla Walla District Hydropower Projects
Project River State Service Rating
Dworshak N/Fork Clearwater ID 1973 400 MW
Ice Harbor Snake WA 1962 651 MW
Little Goose Snake WA 1970 810 MW
Lower Granite Snake WA 1975 810 MW
Lower Monumental Snake WA 1969 810 MW
McNary Columbia OR/WA 1952 980 MW
How electricity is generated
Water flowing downstream at dams produces electricity. As the water passes through the dam’s powerhouse, it falls from the upstream level behind the dam to a lower downstream level. This water is moving with tremendous force and is guided down to the turbine. As it strikes the blades of the turbine, the water turns the turbine like a propeller. The turning turbine spins coils of wires inside a large generator mounted above it, converting the mechanical energy of falling water into electrical energy. Transmission lines then carry the electricity to homes and businesses.