Below-normal precipitation in the upper Missouri Basin during June resulted in slightly below-average June runoff. The 2020 calendar year upper basin runoff forecast, updated on July 1, is 31.2 Million Acre Feet, 121% of average. Average annual runoff for the upper basin is 25.8 MAF.

“The upper basin runoff forecast has been reduced by about 1 MAF due to the recent dry conditions as well as the National Weather Service’s climate outlook, which is indicating that the remainder of the summer will be warmer and drier than normal. However, the 2020 calendar year runoff forecast remains above average, mostly due to the very wet soil conditions during the early months of the year. Most of the mountain snowmelt runoff has entered the reservoir system. Remaining summer runoff will depend on rainfall events,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “As a result of the reduced runoff forecast, we will reduce Gavins Point Dam releases to 30,000 cfs on July 7,” Remus added.

Soils continue to dry out in the upper Missouri River Basin due to well-below normal precipitation and warmer-than-normal temperatures. Drought conditions, based on the National Drought Mitigation Center Drought Monitor, have expanded across much of western portion of the Basin.

The potential for localized flooding remains in the Missouri River Basin. The flooding potential is higher in the lower basin from locally heavy rain on the many uncontrolled tributaries downstream of the Missouri River Mainstem Reservoir System. “I continue to encourage all interested parties to remain aware of the current and forecast conditions by checking the Corps’ Missouri River Basin Water Management and the National Weather Service websites on a routine basis for the most up-to-date information,” said Remus.

As of July 6, the total volume of water stored in the System was 61.5 MAF, up 1.7 MAF since June 1, occupying 5.4 MAF of the System’s 16.3-MAF flood control zone.

Navigation

The July 1 System storage check indicated flow support for the second half of the navigation season will be at least at the full service level for a full-length season. Full service flow support is designed to provide a 9-foot deep by 300-foot wide navigation channel from Sioux City, Iowa to the mouth of the river near St. Louis, Missouri. Flow support is normally provided for an 8-month season from April 1 through December 1 at the mouth.

Mountain Snowpack

As of July 1, the average mountain snowpack was less than 1 inch of snow water equivalent in the reach above Fort Peck and had melted in the reach from Fort Peck to Garrison. The mountain snowpack peaked in both reaches: on April 16 in the Fort Peck reach at 109% of average and on April 19 in the Fort Peck to Garrison reach at 112% of average. The mountain snowpack graphics can be viewed here: https://go.usa.gov/xE6wT.

Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: https://go.usa.gov/xE6wa.

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 last scheduled call for 2020 was held on Thursday, June 4. All calls are recorded in their entirety and are available to the public on the Defense Video and Imagery Distribution System at www.dvidshub.net/unit/usace-nwd.

2019 Summary of Actual Regulation

The Summary of Actual 2019 Regulation of the Missouri River Mainstem Reservoir System Summary is available here: https://go.usa.gov/xwWTY. This document contains a summary of the actual regulation of the Missouri River Mainstem Reservoir System for the 2019 calendar year.

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 33,000 cfs
  • Current release rate – 33,000 cfs (as of July 1)
  • Forecast release rate – 30,000 cfs (month of July)
  • End-of-June reservoir level – 1206.1 feet
  • Forecast end-of-July reservoir level – 1206.0 feet
  • Notes: Releases may adjusted as necessary to offset tributary flows from heavy rain events.
• Fort Randall Dam
  • Average releases past month – 28,600 cfs
  • End-of-May reservoir level – 1355.9 feet
  • Forecast end-of-July reservoir level – 1355.3 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point.
• Big Bend Dam
  • Average releases past month – 25,900 cfs
  • Forecast average release rate – 26,800 cfs
  • Forecast reservoir level – 1420.4 feet
• Oahe Dam
  • Average releases past month – 25,700 cfs
  • Forecast average release rate – 26,900 cfs
  • End-of-June reservoir level – 1611.8 feet
  • Forecast end-of-July reservoir level – 1612.2 feet
• Garrison Dam
  • Average releases past month – 28,000 cfs
  • Current release rate – 28,000 cfs
  • Forecast average release rate – 28,000 cfs
  • End-of-June reservoir level – 1843.5 feet
  • Forecast end-of-July reservoir level – 1844.9 feet
• Fort Peck Dam
  • Average releases past month – 11,000 cfs
  • Current release rate – 11,000 cfs
  • Forecast average release rate – 11,000 cfs
  • End-of-June reservoir level – 2239.6 feet
  • Forecast end-of-July reservoir level – 2240.4 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.

Hydropower:

The six mainstem power plants generated 924 million kWh of electricity in June. Typical energy generation for June is 849 million kWh. The power plants are projected to generate 10.7 billion kWh of electricity 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 http://go.usa.gov/xVgWr.