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2021 runoff forecast remains below average; Virtual spring public meetings April 6

Missouri River Water Management
Published April 6, 2021
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.

Public Meetings are held each spring and fall across the Missouri River basin.

Public Meetings are held each spring and fall across the Missouri River basin. Fall public meetings provide an update on current year's runoff and reservoir operations as well as planned operations for the next year's runoff season. The Annual Operating Plan for the next year's runoff season is released for public comment in September, presented at the public meetings and finalized at the end of the calendar year. Spring public meetings provide a status of mountain snowpack, a runoff forecast for the year, and how operations during the runoff year will meet the authorized purposes for the Missouri River Mainstem System.

Reservoir inflows in the Missouri River basin above Sioux City, Iowa (upper Basin) were well-below average in March. The updated 2021 upper Basin runoff forecast is 21.3 million acre-feet (MAF), 83% of average. 

“Abundant precipitation fell during March in the lower Basin below Sioux City, IA; however, March precipitation was less than 50% of normal over much of the upper Basin,” said John Remus, chief of the U.S. Army Corps of Engineers’, Missouri River Basin Water Management Division. “Due to the lack of plains snowpack in 2021, below-average mountain snowpack, and dry upper Basin conditions, we expect upper Basin runoff to be below average.”

The upper Basin runoff forecast is based on soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.

System storage is currently 56.1 MAF, at the base of the annual flood control zone. The System is positioned to serve all Congressionally authorized purposes during 2021, including flood control, navigation, and water supply. 

Mountain and Plains Snowpack:

Mountain snowpack in the upper Basin is accumulating at below-average rates. The April 1 mountain snowpack in the Fort Peck reach was 88% and the mountain snowpack in the Fort Peck to Garrison reach was 94% of average. By April 1, about 97% of the total mountain snowpack has typically accumulated. Mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC. Currently, plains snowpack in the upper Basin is light.

Navigation:

Gavins Point Dam releases were increased near the end of March to begin flow support for Missouri River navigation. The March 15 System storage indicated that flow support for Missouri River navigation would be at the full-service level for the first half of the 2021 season, in accordance with the guidelines in the Master Manual. Full-service flow support began on April 1 at the mouth of the Missouri River. 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 navigation season length, will be based on the actual July 1 System storage.

Spring Public Meeting:

The spring public meetings will be held virtually on Tuesday, April 6 at 1 p.m. and 6 p.m. CDT by conference call and webinar. The purpose of this meeting is to update the region on current hydrologic conditions and the planned operation of the mainstem reservoir system during the coming months. Links for the virtual public meetings can be found here: https://www.nwd.usace.army.mil/Media/News-Releases/Article/2550171/missouri-river-virtual-spring-public-meetings-to-be-held-april-6/ .

Reservoir Forecasts:

  • Gavins Point Dam
    • Average releases past month – 20,200 cfs
    • Current release rate – 29,000 cfs
    • Forecast release rate – 29,500 cfs
    • End-of-March reservoir level – 1206.5 feet
    • Forecast end-of-April 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.
       
  • Fort Randall Dam
    • Average releases past month – 14,300 cfs
    • End-of-March reservoir level – 1355.0 feet (up 4.5 feet from February)
    • Forecast end-of-April reservoir level – 1355.3 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 – 18,700 cfs
    • Forecast average release rate – 25,500 cfs
    • Forecast reservoir level – 1421.0 feet
       
  • Oahe Dam
    • Average releases past month – 18,200 cfs
    • Forecast average release rate – 25,300 cfs
    • End-of-March reservoir level – 1607.2 feet (up 0.6 foot from February)
    • Forecast end-of-April reservoir level – 1607.2 feet
       
  • Garrison Dam
    • Average releases past month – 18,800 cfs
    • Current release rate – 21,500 cfs
    • Forecast release rate – 21,500 cfs
    • End-of-March reservoir level – 1836.7 feet
    • Forecast end-of-April reservoir level – 1837.2 feet
    • Notes – Releases will be maintained at 21,500 cfs in April.
       
  • Fort Peck Dam
    • Average releases past month – 7,300 cfs
    • Current release rate – 7,500 cfs
    • Forecast average release rate – 7,500 cfs
    • End-of-March reservoir level – 2233.4 feet
    • Forecast end-of-April reservoir level – 2233.9 feet
    • Notes: Releases will be maintained at 7,500 cfs in April.

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 622 million kWh of electricity in March. Typical energy generation for March is 641 million kWh. The power plants are expected to generate 9.5 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 March 31

Change in March

On March 31

% of 1967-2020 Average

Change in March

Fort Peck

2233.4

+0.2

14,658

101

+41

Garrison

1836.7

-0.2

17,525

98

-9

Oahe

1607.2

+0.6

18,622

105

+245

Big Bend

1420.7

-0.4

1,674

98

-21

Fort Randall

1355.0

+4.5

3,407

102

+365

Gavins Point

1206.5

-1.3

338

86

-32

 

 

Total

56,224

101

+589

 

WATER RELEASES AND ENERGY GENERATION FOR MARCH

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

7.3

447

72

Garrison

18.8

1,155

171

Oahe

18.2

1,116

167

Big Bend

18.7

1,149

64

Fort Randall

14.3

880

98

Gavins Point

20.2

1,241

50

 

 

Total

622


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

Release no. 21-018