OMAHA, Neb. (Iowa Media Wire) — Dry conditions on the upper basin of the Missouri River above Sioux City will result in the the minimum amount of water being released from Gavins Point Dam in the winter.
The U.S. Army Corps of Engineers said runoff into the Missouri River was only 86 percent of theaverage for the month of August, measuring 1.2 million acre-feet (MAF). This is after 73 percent of the basin has experienced abnormally dry or drought conditions, which officials expect to continue through November.
Conditions near Sioux City were above average, with the dry conditions mostly impacting the Missouri River dams in Montana and North Dakota.
“Runoff in the Fort Peck and Fort Peck to Garrison reaches were well-below average while runoff in the reaches between Garrison Dam and Sioux City were all above average,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division.
Remus added that August rainfall was mostly normal for the region as there were isolated areas of above normal precipitation in every state except Nebraska.
“Nebraska was generally below average with most of northern Nebraska measuring 50 percent of normal precipitation,” he said.
The forecast for the calendar year has been updated to an expected 23.8 MAF, or 92 percent of the 25.7 MAF average.
As of Sep. 1, there was 55.1 MAF stored in the system consisting of the six dams. This is one MAF below the system’s flood control zone, and officials expect it to continue to decline in the coming months. By the start of the 2025 runoff season, the system storage is expected to be at 47.1 MAF.
Due to the lower runoff near Fort Peck and Garrison, releases will be lowered to 4,000 cubic feet per second (cfs) and 12,000 cfs starting Sep. 16, respectively.
While releases at Gavins Point Dam are currently 33,500 cfs and expected to average 33,900 cfs for the month of September, the lowered releases at Fort Peck and Garrison will ultimately impact the winter releases. Releases at the Yankton dam will be brought down to 12,000 cfs for the winter, the minimum amount that may be released during the season. The Corps will be sending letters to water users below Gavins Point Dam to make them aware of the change in releases.
Releases at Gavins Point Dam are currently 500 cfs below full service for providing navigation flow support to Sioux City, Omaha, Nebraska City, and Kansas City. The support will end Dec. 1 at the mouth of the Missouri River, but the Corps said that flow targets may be missed to conserve water if there is no commercial navigation in areas.
For the month of August, the six mainstem power plants generated 912 million kWh of electricity, while the August average is about 1 billion kWh. The power plants are projected to generate 8.1 billion kWh of electricity this year, about 1.3 billiob kWh below the long-term average.