Above average rainfall and fast-melting snow led to above average runoff in the upper Missouri River Basin last month (June 2023).
Runoff above Sioux City, Iowa, was 122% of average (6.7 million acre-feet).
The annual forecast for the upper basin has been increased due to the rainfall and snowmelt in the month of June, said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. He says the mountain snowpack completely melted out approximately 2 weeks ahead of schedule, further increasing the June runoff.
The annual runoff forecast above Sioux City, Iowa, is currently 114% of average (29.2 MAF and about 2.4 MAF higher than last month’s forecast). Precipitation was normal to much-above-normal in June in much of Montana, southern and east-central North Dakota, and western South Dakota. Below-normal precipitation occurred in eastern South Dakota and into the lower Basin.
The six mainstem power plants generated 690 million kWh of electricity in June, down from the 846 million kWh average energy generation in that month. The power plants are expected to generate 7.9 billion kWh this year, compared to the long-term average of 9.4 billion kWh.
Oahe Dam*
- Average releases past month – 18,200 cfs
- Forecast average release rate – 26,700 cfs
- End-of-June reservoir level – 1604.2 feet (up 2.2 feet from May 31)
- Forecast end-of-July reservoir level – 1603.8 feet
Big Bend Dam*
- Average releases past month – 18,400 cfs
- Forecast average release rate – 26,200 cfs
- Forecast reservoir level – 1420.8 feet
*The forecast reservoir releases and elevations are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.
To view the detailed three-week release forecast for the mainstem dams, go to https://go.usa.gov/xARQB.
The Missouri Basin Web App provides links to these reports and others that are updated more frequently. http://go.usa.gov/xE6fC.
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