US Army Corps of Engineers
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Upper Missouri River basin forecast remains above average

Missouri River Water Management Division
Published June 4, 2020
Runoff can enter the Missouri River anywhere and anytime in the basin. Only when runoff occurs in the upper Missouri River basin can it be captured by the mainstem system of dams. Even then, where runoff is captured depends upon where precipitation falls.

Runoff can enter the Missouri River anywhere and anytime in the basin. Only when runoff occurs in the upper Missouri River basin can it be captured by the mainstem system of dams. Even then, where runoff is captured depends upon where precipitation falls.

Runoff can enter the Missouri River anywhere and anytime in the basin. Only when runoff occurs in the upper Missouri River basin can it be captured by the mainstem system of dams. Even then, where runoff is captured depends upon where precipitation falls.

Runoff can enter the Missouri River anywhere and anytime in the basin. Only when runoff occurs in the upper Missouri River basin can it be captured by the mainstem system of dams. Even then, where runoff is captured depends upon where precipitation falls.

Water releases from Gavins Point Dam will remain at 33,000 cubic feet per second in June, which is about average. May runoff in the upper Basin was about 130% of average; however, the summer climate outlook indicates a return to warmer and drier conditions in the upper Basin.

The 2020 calendar year upper basin runoff forecast is 32.3 million acre feet, 125% of average. “The upper basin runoff forecast remains above average in 2020. The upper basin runoff for the remainder of the year will depend on the mountain snowmelt, which will enter the Fort Peck and Garrison reservoirs in early June, and summer rain events,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “With nearly 80% of the system flood control storage available, the reservoirs are well positioned to capture and manage runoff from the mountain snowmelt and precipitation in the upper Missouri River basin. This also provides the Corps with some added flexibility to respond to rainfall events below the system,” added Remus.

The June 1 forecast is in the top 25% of the 122 years of runoff record. Average annual runoff for the upper basin is 25.8 MAF. The runoff forecast is updated on a monthly basis, and more often if basin conditions warrant.

Soils are drying out in the upper Missouri River Basin, following much wetter-than-normal conditions in 2018 and 2019. The potential for flooding remains in the Missouri River Basin, particularly in the lower river, due to the potential for 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 June 4, the total volume of water stored in the System was 59.9 MAF, up 1.2 MAF since May 1, occupying 3.8 MAF of the System’s 16.3-MAF flood control zone.

Navigation

The March 15 system storage check indicated flow support for Missouri River navigation will be at least full service for the first half of the 2020 season, which began on April 1 at the mouth. Full service flow support 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 navigation season length, will be based on the actual July 1 System storage.

Mountain Snowpack

As of June 1, the mountain snowpack was 84% of average in the reach above Fort Peck and 83% of average 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 next call for 2020 will be held Thursday, June 4, for Congressional delegations; Tribes; state, county and local government officials, levee and drainage districts; and the media. Calls will be recorded in their entirety and made 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 – 33,500 cfs
    • Current release rate – 33,000 cfs (as of June 1)
    • Forecast release rate – 33,000 cfs (month of June)
    • End-of-May reservoir level – 1206.4 feet
    • Forecast end-of-June reservoir level – 1206.1 feet
    • Notes: Releases may adjusted as necessary to offset tributary flows from heavy rain events.
       
  • Fort Randall Dam
    • Average releases past month – 28,300 cfs
    • End-of-May reservoir level – 1355.7 feet
    • Forecast end-of-June reservoir level – 1355.1 feet
    • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point.
       
  • Big Bend Dam
    • Average releases past month – 27,000 cfs
    • Forecast average release rate – 25,200 cfs
    • Forecast reservoir level – 1420.7 feet
       
  • Oahe Dam
    • Average releases past month – 26,800 cfs
    • Forecast average release rate – 25,300 cfs
    • End-of-May reservoir level – 1611.1 feet
    • Forecast end-of-June reservoir level – 1612.8 feet
       
  • Garrison Dam
    • Average releases past month – 26,600 cfs
    • Current release rate – 28,200 cfs
    • Forecast average release rate – 28,000 cfs
    • End-of-May reservoir level – 1840.8 feet
    • Forecast end-of-June reservoir level – 1844.0 feet
       
  • Fort Peck Dam
    • Average releases past month – 9,200 cfs
    • Current release rate – 11,200 cfs
    • Forecast average release rate – 11,000 cfs
    • End-of-May reservoir level – 2238.0 feet
    • Forecast end-of-June reservoir level – 2240.9 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 930 million kWh of electricity in May. Typical energy generation for May is 794 million kWh. The power plants are projected to generate 11.0 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.

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 1967-2019 Average

Change in May

Fort Peck

2238.0

+1.7

15,655

108

+413

Garrison

1840.8

+0.5

18,797

105

+188

Oahe

1611.1

+1.2

19,856

112

+418

Big Bend

1420.8

+0.3

1,677

98

+17

Fort Randall

1355.7

+1.3

3,470

104

+110

Gavins Point

1206.4

+0.1

337

86

+3

 

 

Total

59,792

108

+1,149

 

 

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

9.2

568

93

Garrison

26.6

1,634

253

Oahe

26.8

1,648

253

Big Bend

27.0

1,663

92

Fort Randall

28.3

1,740

187

Gavins Point

33.5

2,058

52

 

 

Total

930


Contact
Eileen Williamson
402-996-3802
eileen.l.williamson@usace.army.mil

Release no. 20-066