March 2026 runoff in the Missouri River Basin above Sioux City, IA, was 56% of average– or 1.7 million acre-feet.
The updated 2026 calendar year runoff for the upper Missouri River Basin continues to be below normal, now estimated to be 69% 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 U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division, says conditions across most of the basin remain dry. He says mountain snowpack has decreased as well, and is currently below the 30-year minimum accumulation.
The six mainstem power plants– including the Oahe Dam at Pierre and Fort Pierre– generated 596 million kWh of electricity in March, 40 million kWh lower than the typical energy generation in March of 636 million kWh. Electricity generation for 2026 is estimated at 7.3 billion kWh compared to the long-term average of 9.3 billion kWh.
Remus says mountain snowpack in the upper Missouri River Basin is accumulating at below average rates. By April 1, about 96% of the total mountain snowfall has typically accumulated. Mountain snow normally peaks near April 17.
The volume of water stored in the Missouri River Mainstem Reservoir System is currently 49.5 MAF, 6.6 MAF below the top of the carryover multiple use zone. 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:
- Big Bend Dam
- Average releases past month – 20,800 cfs
- Forecast average release rate – 24,600 cfs
- Forecast reservoir level – 1420.4 feet
- Oahe Dam
- Average releases past month – 20,800 cfs
- Forecast average release rate – 24,600 cfs
- End-of-March reservoir level – 1601.4 feet
- Forecast end-of-April reservoir level – 1600.5 feet
The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.
Related Link: Missouri River Web App
Related Link: 3 Week Forecast
Related Link: Mountain Snowpack
Courtesy infographic.
Courtesy infographic.
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