US Army Corps of Engineers
Northwestern Division Website

News Releases

Below average runoff continues in the upper Missouri River basin

Missouri River Water Management
Published Oct. 5, 2020
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.

September precipitation was well-below normal in the Missouri River Basin.  As a result, September runoff in the upper Missouri River Basin above Sioux City, Iowa was 69% of average. 

Since January 1, precipitation in the upper Basin is well-below normal.  The National Weather Service’s Climate Prediction Center is forecasting that below-normal precipitation will continue in October.  The 2020 calendar year runoff forecast for the upper Basin, updated on Oct. 1, is 30.2 million acre-feet (MAF), 117% of average. Average annual runoff for the upper Basin is 25.8 MAF.

“Upper basin runoff was below average in September. We expect runoff to be below average during the remainder of the calendar year. Lower basin runoff has been below average as well,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.  “Releases from Gavins Point Dam are being made to meet full service Missouri River navigation flow targets”, Remus added. 

The navigation flow support season ends on December 1 at the mouth of the Missouri River. 

As of Oct. 5, the total volume of water stored in the System was 58.6 MAF, occupying 2.5 MAF of the System’s 16.3-MAF flood control zone. System storage peaked at 61.8 MAF on July 16 and will decline during the fall. All 16.3 MAF of flood control storage is expected to be available prior to the start of the 2021 runoff season. If fall and winter runoff continues to be below average as forecasted, System storage will be about 0.8 MAF below the base of the annual flood control zone by the start of the 2021 runoff season.

According to the National Drought Mitigation Center (NDMC), drought conditions continue to worsen across much of the upper Basin. Wide-spread areas of drought classified as Extreme are evident in Colorado and Wyoming.  Moderate to Severe drought conditions are present in large areas of Montana, North Dakota, South Dakota, Nebraska and Iowa.

Navigation

The July 1 System storage check indicated flow support for the second half of the navigation season would be at least at the full service level for a full-length 8-month flow support season. Full service flow support is designed to work in tandem with the Missouri River Bank Stabilization and Navigation Project to provide a 9-feet deep by 300-foot wide navigation channel from Sioux City, Iowa to the mouth of the river near St. Louis, Missouri. Gavins Point releases will be reduced to winter levels beginning around Nov. 22.

Winter Release Rate

The winter release rate is determined based on the Sept. 1 System storage. Per the Sept. 1 System storage, winter releases from Gavins Point Dam will be at least 17,000 cfs.

Fall Public Meetings

Two public meetings will be conducted by webinar on Nov. 2. The purpose of these meetings is to update the region on current hydrologic conditions and the planned operation of the mainstem reservoir system during the remaining fall months as well as present the draft plans for operating the System during 2021. Meeting times and webinar information will be at the following link when it becomes available: https://www.nwd.usace.army.mil/MRWM/Public-Meetings/.

Reservoir Forecasts:

  • Gavins Point Dam
    • Average releases past month – 32,200 cfs
    • Current release rate – 32,500 cfs (as of October 1)
    • Forecast release rate – 33,000 cfs (month of October)
    • End-of-September reservoir level – 1207.5 feet
    • Forecast end-of-October reservoir level – 1207.5 feet
    • Note: Releases will be adjusted as necessary to meet all downstream navigation targets.
       
  • Fort Randall Dam
    • Average releases past month – 30,500 cfs
    • End-of-September reservoir level – 1353.5 feet
    • Forecast end-of-October reservoir level – 1344.6 feet
    • Note: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The Fort Randall pool is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend. The annual drawdown will continue in October and November.
       
  • Big Bend Dam
    • Average releases past month – 28,500 cfs
    • Forecast average release rate – 20,200 cfs
    • Forecast reservoir level – 1420.7 feet
       
  • Oahe Dam
    • Average releases past month – 28,900 cfs
    • Forecast average release rate – 20,300 cfs
    • End-of-September reservoir level – 1610.4 feet
    • Forecast end-of-October reservoir level – 1608.5 feet
    • Notes: Oahe will undergo a full powerplant outage during the day on October 13 to conduct scheduled maintenance.  Zero releases, though not unusual from Oahe, will be scheduled during the daylight hours so that the work crew can complete maintenance in the tailrace area. 
       
  • Garrison Dam
    • Average releases past month – 17,900 cfs
    • Current release rate – 14,000 cfs
    • Forecast average release rate – reduce to 13,000 cfs on 8 October
    • End-of-September reservoir level – 1839.7 feet
    • Forecast end-of-October reservoir level – 1839.3 feet
       
  • Fort Peck Dam
    • Average releases past month – 8,400 cfs
    • Current release rate – 6,000 cfs
    • Forecast average release rate – 6,000 cfs
    • End-of-September reservoir level – 2237.7 feet
    • Forecast end-of-October reservoir level – 2237.1 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 875 million kWh of electricity in September. Typical energy generation for September is 905 million kWh. The power plants are projected to generate 10.1 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 September 30

Change in September

On September 30

% of 1967-2019 Average

Change in September

Fort Peck

2237.7

-1.0

15,582

108

-215

Garrison

1839.7

-1.0

18,433

103

-350

Oahe

1610.4

-1.9

19,489

110

-748

Big Bend

1420.7

0.0

1,677

98

+3

Fort Randall

1353.5

-1.7

3,281

98

-152

Gavins Point

1207.6

+0.8

363

93

+18

 

 

Total

58,825

106

-1,444

 

 

WATER RELEASES AND ENERGY GENERATION FOR SEPTEMBER

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

8.4

498

82

Garrison

17.9

1,063

158

Oahe

29.0

1,723

267

Big Bend

28.5

1,697

93

Fort Randall

30.5

1,813

192

Gavins Point

32.2

1,919

82

 

 

Total

874


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

Release no. 20-140