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Corps: Missouri River power output below average in 2021

February 3, 2022 GMT

BISMARCK, N.D. (AP) — Electric power generation from the Missouri River’s six upstream dams fell below average in 2021, forcing the federal agency that sells the power to buy electricity on the open market to fulfill contracts — a cost that may ultimately be passed on to ratepayers in a half-dozen states.

The U.S. Army Corps of Engineers manages dams and reservoirs along the 2,341-mile river. Mike Swenson, a Corps engineer in Omaha, Nebraska, said Thursday that energy production from the dams in the Dakotas, Montana and Nebraska was below average because water was kept in reservoirs to make up for drought conditions.

Energy production totaled 8.6 billion kilowatts of electricity in 2021, down from 10.1 billion kilowatts in 2020. A billion kilowatt-hours of power is enough to supply about 86,000 homes for a year.

The dams have generated an average of about 9.4 billion kilowatt-hours of electricity since 1967, including a high of 14.6 billion kilowatts in 1997. During the driest years this century, power plant output dwindled below 5 billion kilowatt-hours in 2007 and 2008, the Corps said.

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The Western Area Power Administration sells power from 57 hydropower plants around the nation. The Missouri River dams are its second-largest producer of energy, which is sold to 350 customers that include rural electric cooperatives, municipal utilities, Native American tribes and others in the Dakotas, Montana, Minnesota, Iowa and Nebraska. The shortfall in electricity production from hydropower meant the agency had to get energy from other, more expensive sources, said spokeswoman Lisa Meiman.

The agency bought $18 million of electricity on the open market in fiscal 2021 that ended Sept. 30, data show.

The cost to individual ratepayers likely would be minimal, Meiman said.

Purchasing power to fulfill contracts is not unusual. The Western Area Power Administration has spent $1.5 billion since 2000 to fulfill contracts due to shallow river levels caused by drought, Meiman said.

Oahe Dam near Pierre, South Dakota, which holds Lake Oahe, and Garrison Dam, which creates Lake Sakakawea in North Dakota, are typically the biggest power producers in the Missouri River system.

Swenson said Oahe Dam generated 2.4 billion kilowatt-hours last year, down from the long-term average of 2.7 kilowatt-hours. Garrison Dam generated 2 billion kilowatt-hours of electricity last year, down from long-term average of 2.3 billion kilowatt-hours, he said.

The Corps is charged with finding a balance between upstream states, which want water held in reservoirs to support fish reproduction and recreation, and downstream states, which want more water released from the dams, mainly to support barge traffic.

Swenson said 2021 “started off close to normal” for Missouri River levels, but the Corps began holding back water in July because of dry weather.

The water storage level of the six upstream reservoirs is about 48 million acre-feet at present, or about 15% below the ideal level, Swenson said. An acre-foot is the amount of water covering one acre, a foot deep.

Based on runoff estimates for 2022, the Corps has forecast 7.4 billion kilowatt-hours of electricity this year, or about 15% below 2021.