July runoff in the Missouri River basin above Sioux City, Iowa was 3.3 million acre-feet (MAF), 99% of average.  Runoff was near or above average in all reaches except the Fort Peck reach, which was 68% of average.  

“Soil moisture conditions deteriorated in Montana, North Dakota, and northern South Dakota over the last month and improved across southern South Dakota and into the lower basin,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. 

Precipitation was below normal over most of the upper Missouri River basin last month except for small areas in Wyoming and southern South Dakota.  The lower basin saw a mix of above- and below-normal precipitation. 

The annual runoff forecast above Sioux City, Iowa is 28.5 MAF, 111% of average.

System storage peaked on July 22 at 56.6 MAF.  System storage on August 1 was 56.3 MAF, 0.2 MAF above the base of the Annual Flood Control and Multiple Use zone. 

“Reservoir inflows in July declined due to warmer and drier conditions in the upper Missouri River basin.  After peaking in late July, System storage is expected to continue declining into the Carryover Multiple Use Zone during the remainder of 2023 as we make releases during the summer and fall periods to meet the authorized purposes,” said Remus. 

“The monthly study indicates that the winter release from Gavins Point, which is based on the Sept. 1 System storage check, will likely be near the minimum rate of 12,000 cfs,” added Remus.

Basin and river conditions continue to be monitored and System regulation will be adjusted based on the most up-to-date information. 

Navigation:

Per the July 1 System storage check, navigation flow support was increased to 1,500 cfs below the full-service level. The flow support season length will be a full 8-month season, ending December 1 at the mouth of the Missouri River.   Gavins Point Dam releases are currently 31,500 cfs.  Releases will be set to provide flow support at the intermediate-service level at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City).

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 29,000 cfs
  • Current release rate – 31,500 cfs
  • Forecast release rate – 33,000 cfs
  • End-of-July reservoir level – 1206.5 feet
  • Forecast end-of-August reservoir level – 1206.5 feet
  • Notes: The Gavins Point release will be adjusted to provide navigation flow support on the lower Missouri River.
     
• Fort Randall Dam
  • Average releases past month – 26,600 cfs
  • End-of-July reservoir level – 1355.0 feet
  • Forecast end-of-August reservoir level – 1355.2 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 – 25,400 cfs
  • Forecast average release rate – 31,800 cfs
  • Forecast end-of-August reservoir level – 1420.5 feet
     
• Oahe Dam
  • Average releases past month – 25,700 cfs
  • Forecast average release rate – 32,000 cfs
  • End-of-July reservoir level – 1603.7 feet (down 0.5 feet from June 30)
  • Forecast end-of-August reservoir level – 1601.5 feet
     
• Garrison Dam
  • Average releases past month – 21,800 cfs
  • Current release rate – 22,000 cfs
  • Forecast release rate – 22,000 cfs
  • End-of-July reservoir level – 1842.4 feet (up 2.8 feet from June 30)
  • Forecast end-of-August reservoir level – 1841.7 feet
  • Notes – Releases will be maintained at 22,000 cfs through mid-September.
     
• Fort Peck Dam
  • Average releases past month – 8,800 cfs
  • Current release rate – 9,000 cfs
  • Forecast average release rate – 7,500 cfs
  • End-of-July reservoir level – 2230.4 feet (down 0.2 feet from June 30)
  • Forecast end-of-August reservoir level – 2229.0 feet
  • Notes: Releases will be maintained at 7,500 cfs through September.

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 877 million kWh of electricity in July. Typical energy generation for July is 956 million kWh. The power plants are expected to generate 7.8 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