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Upper basin runoff forecast continues to be below average

Missouri River Water Management Division
Published June 3, 2021
Updated: June 14, 2021
System storage is 55.2 MAF, 0.2 MAF more than last week.
Upper Basin runoff in May was about 60% of average 
Mountain snowpack has peaked in both reaches and is starting to melt (lower right quadrant). Runoff is expected to increase slightly during June.
The latest drought outlook (upper right quadrant) indicates that drought conditions are expected to persist in the upper Basin in June.
As per the Master Manual, Gavins Point releases are being made to meet full-service navigation flow targets.
The runoff forecast of 17.9 MAF is 69% of average. The monthly studies indicate that drought conservation
measures of reduced navigation flow support will be enacted on July 1.

System storage is 55.2 MAF, 0.2 MAF more than last week. Upper Basin runoff in May was about 60% of average Mountain snowpack has peaked in both reaches and is starting to melt (lower right quadrant). Runoff is expected to increase slightly during June. The latest drought outlook (upper right quadrant) indicates that drought conditions are expected to persist in the upper Basin in June. As per the Master Manual, Gavins Point releases are being made to meet full-service navigation flow targets. The runoff forecast of 17.9 MAF is 69% of average. The monthly studies indicate that drought conservation measures of reduced navigation flow support will be enacted on July 1.

After our June communication materials were sent, we received a few calls from the public seeking clarification on planned releases from Gavins Point Dam.

“I want to clarify these points. The service level for the second half of the navigation season is based on the July 1st storage check. Based on the June 1st runoff forecast and monthly studies, we anticipate less than full-service navigation flow support starting July 1 while still providing a full 8-month navigation flow support season. Winter releases, which usually begin in December, are based on the September 1st storage check. Based on the current forecasts winter releases from Gavins Point Dam are expected to be at the minimum rate of 12,000 cfs,” said John Remus, chief of water management for the Missouri River Water Management Division.

Below are links to the the recording of the call held for key stakeholders on June 3, the slides from that call, and the letter that was mailed to lower river water users.

We will provide our next update on July 8 and encourage the public to check our website for the most accurate and up-to-date information regarding operations of the Missouri River Mainstem System of dams at https://www.nwd.usace.army.mil/MRWM/MRWMApp/.


Below-average precipitation and dry soil conditions persist in the upper Missouri River Basin above Sioux City, Iowa (upper Basin).

The updated 2021 upper Basin runoff forecast is 17.9 million acre-feet (MAF), 69% of average. If realized, this runoff amount would be in the 22nd driest year in the upper Basin since 1898. The May upper Basin runoff was 64% of average. May runoff in the Fort Peck and Garrison reaches, where much of the upper Basin runoff from mountain snowmelt originates, was 60% and 68% of average, respectively.

“Per our June 1 upper Basin forecast, we expect runoff to continue to be well-below average through the summer and fall,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.

“The June 1 reservoir studies indicate the navigation service level, based on the July 1 System storage check, will be reduced by approximately 1,000 cubic feet per second (cfs) for the second half of the navigation season. The studies also indicate that the winter release from Gavins Point will be at minimum levels, which is 12,000 cfs.”

System storage is currently 55.2 MAF, 0.9 MAF below the base of the Annual Flood Control and Multiple Use Zone. System storage is expected to remain in the Carryover Multiple Use Zone during 2021. 

Mountain Snowpack:
Mountain snowpack in the upper Basin was below the June 1 average and is melting rapidly. The mountain snowpack peaked above Fort Peck in late March at 86% of average, while the mountain snowpack in the Fort Peck to Garrison reach peaked in late April at 96% of average. Mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.

Navigation:
Gavins Point Dam releases will provide full-service navigation flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City) through July 1. Full-service flow support, in combination with the Bank Stabilization and Navigation Project, is generally sufficient to provide a 9-foot-deep by 300-foot-wide channel. Flow support for the second half of the navigation season, as well as the navigation season length, will be based on the actual July 1 System storage. If the June 1 runoff forecast is realized, navigation flow support would be lowered about 1000 cfs below the full-service levels for the second half of the season. The season length will be a full 8-month season.

Winter Release Rate:
The winter release rate is determined based on the Sept. 1 System storage. Per the reservoir studies, if the June runoff forecast and reservoir studies are realized, the winter releases from Gavins Point Dam will be at the minimum rate of 12,000 cfs.

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 2021 will be held on Thursday, June 3. 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 – 29,400 cfs
    • Current release rate – 29,500 cfs
    • Forecast release rate – 30,000 cfs
    • End-of-May reservoir level – 1206.5 feet
    • Forecast end-of-June reservoir level – 1206.0 feet
    • Notes: The Gavins Point release will be adjusted to provide full-service navigation flow support on the lower Missouri River through July 1, the first half of the navigation season.
       
  • Fort Randall Dam
    • Average releases past month – 25,800 cfs
    • End-of-May reservoir level – 1355.2 feet (up 0.3 foot from April 30)
    • Forecast end-of-June 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 – 25,300 cfs
    • Forecast average release rate – 25,100 cfs
    • Forecast reservoir level – 1420.6 feet
       
  • Oahe Dam
    • Average releases past month – 26,000 cfs
    • Forecast average release rate – 25,000 cfs
    • End-of-May reservoir level – 1605.9 feet (down 0.5 foot from April 30)
    • Forecast end-of-June reservoir level – 1606.2 feet
       
  • Garrison Dam
    • Average releases past month – 21,900 cfs
    • Current release rate – 22,000 cfs
    • Forecast release rate – 22,000 cfs
    • End-of-May reservoir level – 1835.2 feet
    • Forecast end-of-June reservoir level – 1837.0 feet
    • Notes – Releases will be maintained at 22,000 cfs through August.
       
  • Fort Peck Dam
    • Average releases past month – 8,400 cfs
    • Current release rate – 9,500 cfs
    • Forecast average release rate – 9,500 cfs
    • End-of-May reservoir level – 2233.0 feet
    • Forecast end-of-June reservoir level – 2233.1 feet
    • Notes: Releases will be maintained at 9,500 cfs through August.

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 832 million kWh of electricity in May. Typical energy generation for May is 797 million kWh. The power plants are expected to generate 8.8 billion kWh this year, compared to the long-term average of 9.5 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

MISSOURI RIVER MAINSTEM RESERVOIR DATA

 

Pool Elevation
(feet above mean sea level)

Water in Storage
(1,000 acre-feet)

 

On May 31

Change in May

On May 31

% of 1967-2020 Average

Change in May

Fort Peck

2233.0

0.0

14,581

100

+10

Garrison

1835.2

0.0

17,015

95

-62

Oahe

1605.9

-0.5

18,160

102

-183

Big Bend

1420.8

+0.4

1,680

99

+24

Fort Randall

1355.2

+0.3

3,425

103

+22

Gavins Point

1206.5

0.0

339

87

-1

 

 

Total

55,200

99

-190

 

WATER RELEASES AND ENERGY GENERATION FOR MAY

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

8.4

516

85

Garrison

21.9

1,349

199

Oahe

26.0

1,601

238

Big Bend

25.3

1,557

86

Fort Randall

25.8

1,587

170

Gavins Point

29.4

1,809

54

 

 

Total

832


Contact
Eileen Williamson
402-779-1448
eileen.l.williamson@usace.army.mil

Release no. 21-021