Water releases from Gavins Point Dam on the Missouri River will be dialed back again this winter as drought conditions continue to affect the northern Great Plains.
Winter flows from the northeast Nebraska dam will be at minimum levels, averaging nearly 12,000 cubic feet per second from December through February, the U.S. Army Corps of Engineers said last week.
When the reservoir system is full, Gavins Point winter releases out of Lewis and Clark Lake generally are near 17,000 cfs, or higher if flood water is being evacuated. Temporary increases above 12,000 cfs will be provided as needed this winter to push ice away from municipal water intakes.
The lower flows have little impact in the channel during winter because there is no barge traffic on the river in the Omaha region.
Based on reservoir storage conditions July 1, the corps is providing a full eight-month navigation season for barges south of Sioux City, Iowa. The season ends this fall.
Drought conditions continue to affect a large portion of the upper basin, said Mike Swenson in the corps' Omaha water management office.
Though runoff into the river above Sioux City was 107 percent of normal during August, the calendar year runoff forecast remains at 91 percent of normal.
Reservoir levels at the upper three large reservoirs — Fort Peck, Garrison and Oahe in Montana and the Dakotas — are 3 to 9 feet below their desired elevations, Swenson said.
He said the corps will continue to monitor basin conditions and fine-tune the regulation of the reservoir system based on the latest information.
Upstream from Gavins Point, at Fort Randall Dam in southeast South Dakota, the reservoir is expected to decrease nearly 2feet this month to provide space for winter hydropower generation at Oahe and Big Bend reservoirs. The annual drawdown will continue in October and November.
The Oahe reservoir is expected to drop more than 3 feet during September.
The drought also affects the corps' six mainstem power plants. The power plants are projected to generate 7.6 billion kilowatt hours of electricity this year, compared with the normal of 10 billion kilowatt hours.