Missouri River Basin Water Management U.S. Army Corps of Engineers, Northwestern Division

Extremely high unregulated tributary flows following heavy rains have led to destructive flooding along the tributaries and will send floodwaters into the Missouri River. Fort Randall Dam is operating with minimal releases and Gavins Point dam continues releases at 24,000 cfs with 15,000 cfs through the spillway and 9,000 cfs through the powerhouse. Even with the lower than normal release, high flows more than 90,000 cfs on the unregulated Big Sioux River are contributing to high stage forecasts on the Missouri River.

Extremely high unregulated tributary flows following heavy rains have led to destructive flooding along the tributaries and will send floodwaters into the Missouri River. Fort Randall Dam is operating with minimal releases and Gavins Point dam has releases lowered to 24,000 cfs with 15,000 cfs through the spillway and 9,000 cfs through the powerhouse. Even with the lower than normal release, high flows more than 90,000 cfs on the unregulated Big Sioux River are contributing to high stage forecasts on the Missouri River.

Heavy rains rainfall and forecast inflows into the Gavins Point reservoir from the Niobrara River, and other tributaries, have spurred release changes at Fort Randall and Gavins Point dams. Additionally, the Omaha District and Kansas City District Emergency Operations Centers have activated to provide response to local communities.

Test flows from Fort Peck Dam to comply with the 2018 Biological Opinion were recommenced Monday, June 17 after a delay due to the Missouri River gage at Williston's forecast stage of 22.6 feet on June 15. Once river stages dropped below 22 feet, the test flow's second peak resumed but with a lower peak set at Wolf Point, Montana of 20,000 cfs. 2,500 cfs lower than the initially planned peak.

Test flows from Fort Peck Dam to comply with the 2018 Biological Opinion were scheduled to start increasing this week to 22,000 cfs. However, flow increases are delayed due to the Missouri River gage at Williston's forecast stage of 22.6 feet on June 15. A test protocol halts or delays release increases if the Williston gage is forecast to go about 22 feet.

May runoff for the Basin above Sioux City, Iowa was 3.5 MAF,104% of average. The annual runoff forecast above Sioux City, Iowa is 21.0 MAF, 82% of average, and 1.8 MAF higher than last month’s forecast. System storage is currently 55.0 MAF, 1.1 MAF below the top of the carryover multiple use zone. During May, System storage increased 1.0 MAF.