Corps sets Missouri River winter releases at minimum; low water expected from late November
Don Harrold, Executive Editor
editor@enterprisepub.com
The U.S. Army Corps of Engineers will reduce Missouri River flows this fall and hold winter releases at the lowest rate its operating manual allows, a schedule that will lower river levels past Harrison County from late November through spring.
Winter releases from Gavins Point Dam near Yankton, S.D., will be at least 12,000 cubic feet per second beginning Dec. 1. The rate is set by the volume of water in the reservoir system on Sept. 1, which was 47.2 million acre-feet.
Before that, navigation flow support ends Nov. 15 at the mouth of the Missouri River, two weeks earlier than the usual Dec. 1 close. The Corps shortened the season by 15 days because of low system storage and has provided flow support at minimum service at all four target locations this year: Sioux City, Omaha, Nebraska City and Kansas City.
Between the end of navigation support and Dec. 1, Gavins Point releases may be reduced to a water supply rate of 9,000 cfs for about two weeks. The Corps said it will monitor tributary flows below Gavins Point during that period and adjust releases if downstream flows are insufficient.
Gavins Point was releasing 28,000 cfs on Sept. 13, according to the Corps' daily river bulletin. The bulletin listed the Missouri River at Omaha at 31,256 cfs and at Decatur, Neb., at 30,842 cfs. The Blair gage (a fixed station measuring river height; "gage" is the Corps' longstanding spelling of "gauge"), at river mile 648, read 14.3 feet. Flood stage there is 26.5 feet.
Tributaries in the county were running low. The Boyer River at Logan was estimated at 232 cfs and the Soldier River at Pisgah at 83 cfs.
The Corps said it sent letters in September to water users below Gavins Point Dam notifying them of the planned fall and winter releases and encouraging them to assess the risk to their facilities.
The U.S. Drought Monitor shows more than 83 percent of the Missouri River basin is abnormally dry or in drought. A year ago the figure was about 41 percent. Severe drought or worse covered about 35 percent of the basin on Sept. 1, compared with about 5 percent a year earlier.
Runoff above Sioux City for the 2026 calendar year is forecast at 15.4 million acre-feet, 60 percent of average. The long-term average is 25.7 million acre-feet. August runoff was 1.0 million acre-feet, 73 percent of average.
Mountain snowpack in the two headwater reaches peaked March 16, about a month earlier than normal, at 77 percent of normal above Fort Peck and 79 percent in the Fort Peck to Garrison reach. Both reaches were free of snow by June 25.
John Remus, chief of the Corps' Missouri River Basin Water Management Division, said in the agency's September update that reservoir levels dropped 1 to 2 feet in August and that "System storage will continue to decline this fall."
Above-normal rainfall in August fell largely below the storage reservoirs. The Corps said that rain allowed it to meet reduced navigation targets at lower release rates.
In its September runoff forecast narrative, the Corps said that if September runoff into the Garrison reach comes in as projected, it would be the second lowest on record for the month.
The six mainstem power plants generated 762 million kilowatt-hours in August, against a typical August figure of 1,000 million. Annual generation is projected at 7.1 billion kilowatt-hours, compared with a long-term average of 9.3 billion.
Sen. John Hoeven, R-N.D., has asked the Corps to take additional conservation measures this fall and winter. Lake Sakakawea, behind Garrison Dam, was at 1,824.97 feet on Sept. 9, about 12.5 feet below the top of its normal conservation pool, and the Corps forecasts it will fall about 5 feet more by the end of February 2027.
Hoeven said in a statement that the Corps has minimized flows out of the upper basin but that "more needs to be done," citing irrigation needs and lake access.
The Corps reduced the Garrison Dam release from 17,000 cfs to 13,000 cfs beginning Sept. 14. Water released from Garrison travels through Lake Oahe, Lake Sharpe and Lake Francis Case before reaching Gavins Point, the last dam above Harrison County.
The Corps projects system storage will be 43.8 million acre-feet at the start of the 2027 runoff season, about 12.3 million acre-feet below the base of flood control. Storage levels are checked March 15, July 1 and Sept. 1 each year to set navigation service levels and the winter release rate.
Soil moisture is below normal across most of the basin, which the Corps uses as an indicator of late winter and early spring runoff potential. Forecasters put the chance of a strong El Niño during the fall and winter of 2026-27 at 90 percent. The Corps said El Niño winters typically shift the storm track across Canada, producing warmer temperatures and less snowfall in the basin. Its seasonal outlook shows drought improving in Colorado, southern Wyoming and western Nebraska and Kansas by the end of November.
The Corps' Northwestern Division has scheduled public meetings for the last week of October. Dates and locations had not been set as of the agency's Sept. 4 release.
Daily gage readings and dam releases, along with a three-week release forecast, are published on the Missouri River Basin Water Management website. The Sept. 10 conference call was the last scheduled for 2026; a recording and slides are posted online.
Corps contact: Eileen Williamson, 402-996-3802.
Sources: U.S. Army Corps of Engineers Missouri River Basin Water Management September 2026 monthly update, September 2026 calendar year runoff forecast narrative, and daily river bulletin for Sept. 13, 2026; U.S. Drought Monitor; statement from the office of Sen. John Hoeven.
