Late season plains snowpack accumulation and subsequent melting led to increased runoff throughout the upper Missouri River Basin during April. For the month, runoff was 4.7 million acre-feet, 159% of average, for the basin above Sioux City, IA.

“The runoff forecast continues to improve thanks to late season plains and mountain snowfall in the upper basin,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “We hope to see the precipitation trend continue to provide the much needed moisture for the region.”

The annual runoff forecast for the upper Missouri River Basin above Sioux City, IA is 26.9 MAF, 105% of average, and 0.5 MAF higher than last month’s forecast. However, soil moisture remains slightly below normal in eastern Montana and the western Dakotas, and well below normal in Nebraska. Even with the plains snowmelt, soils dried out in late April over a large portion of the upper basin.

“Despite the additional moisture, much of the upper basin remains in drought and is forecast to remain in drought through the month of May. The System is still recovering from drought as we continue to serve all Congressionally authorized purposes,” said Remus.

System storage is currently 49.6 MAF, 6.5 MAF below the top of the carryover multiple use zone. During April, System storage increased 3.0 MAF. Basin and river conditions continue to be monitored and System regulation will be adjusted based on the most up-to-date information.

Mountain Snowpack:
The mountain snowpack appeared to have peaked in early April, but cooler weather and additional storms resulted in additional snowpack accumulation. The Fort Peck reach peaked at 117% of normal on April 24 and has 88% of the peak remaining. The Garrison reach peaked at 109% of normal on April 6 and has 85% of the peak remaining. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.

Navigation:
Gavins Point Dam releases will continue to provide minimum-service navigation flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City) for the first half of the navigation season. The flow support season began April 1 at the mouth of the river near St. Louis, Missouri. The service level was based on the total volume of water stored within the System on March 15, which was 46.3 MAF, in accordance with the guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as navigation season length, will be based on the storage in the System on July 1.

Monthly Water Management Conference Calls
Water management calls include an update from the National Weather Service’s Missouri Basin River Forecast Center, and an update on the Missouri River mainstem reservoir system operations. The next call for 2023 will be held Thursday, May 11. All calls are recorded in their entirety and are available to the public on our website at https://go.usa.gov/xARQv.

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 16,500 cfs
  • Current release rate – 17,500 cfs
  • Forecast release rate – 20,500 cfs
  • End-of-April reservoir level – 1206.1 feet
  • Forecast end-of-May reservoir level – 1206.0 feet
  • Notes: The Gavins Point release will be adjusted to provide minimum-service navigation flow support on the lower Missouri River.
     
• Fort Randall Dam
  • Average releases past month – 13,100 cfs
  • End-of-April reservoir level – 1355.1 feet
  • Forecast end-of-May reservoir level – 1355.1 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up Gavins Point releases.
     
• Big Bend Dam
  • Average releases past month – 10,300 cfs
  • Forecast average release rate – 14,300 cfs
  • Forecast reservoir level – 1420.9 feet
     
• Oahe Dam
  • Average releases past month – 9,100 cfs
  • Forecast average release rate – 14,200 cfs
  • End-of-April reservoir level – 1599.8 feet
  • Forecast end-of-May reservoir level – 1602.1 feet
     
• Garrison Dam
  • Average releases past month – 16,600 cfs
  • Current release rate – 17,000 cfs
  • Forecast release rate – 19,500 cfs
  • End-of-April reservoir level –1829.2 feet
  • Forecast end-of-May reservoir level – 1830.5 feet
  • Notes – Releases will be increased to 22,000 cfs in mid-May.
     
• Fort Peck Dam
  • Average releases past month – 5,000 cfs
  • Current release rate – 6,000 cfs
  • Forecast average release rate – 6,900 cfs
  • End-of-April reservoir level – 2221.9 feet
  • Forecast end-of-May reservoir level – 2224.0 feet
  • Notes: Releases will be gradually increased to 9,000 cfs by mid-May.

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.

Hydropower:
The six mainstem power plants generated 425 million kWh of electricity in April. Typical energy generation for April is 699 million kWh. The power plants are expected to generate 7.6 billion kWh this year, compared to the long-term average of 9.4 billion kWh.

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