The United States Army Corps of Engineers says April 2026 runoff in the Missouri River Basin above Sioux City, IA, was 51% of average– or 1.5 million acre-feet.
The updated 2026 calendar year runoff for the upper Missouri River Basin continues to be below normal, now estimated to be 67% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.
John Remus, chief of the Corps’ Missouri River Basin Water Management Division, says dry conditions are present in 74% of the basin. He says drought conditions are expected to persist through July with some expansion likely in Montana and South Dakota. As a result, the runoff forecast was lowered by 0.7 MAF from last month.
The six mainstem power plants– including the Oahe Dam at Pierre and Fort Pierre and Big Bend Dam near Fort Thompson– generated 648 million kWh of electricity in April, 48 million kWh lower than the typical energy generation in April of 696 million kWh. Electricity generation for 2026 is estimated at 7.3 billion kWh compared to the long-term average of 9.3 billion kWh.
Basin and river conditions continue to be monitored, including plains and mountain snow accumulation, and System regulation will be adjusted based on the most up-to-date information.
Reservoir Forecasts (These are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.):
- Big Bend Dam
- Average releases past month – 23,100 cfs
- Forecast average release rate – 21,200 cfs
- Forecast reservoir level – 1421.0 feet
- Oahe Dam
- Average releases past month – 23,200 cfs
- Forecast average release rate – 21,400 cfs
- End-of-April reservoir level – 1600.1 feet (down 1.3 feet since March 31)
- Forecast end-of-May reservoir level – 1599.5 feet
To view the detailed three-week release forecast for the mainstem dams, go to https://go.mil/mr-3wk-fcast.
The mountain snowpack graphics can be viewed at: https://go.mil/mr-mtn-snowpack.
Comments