US Army Corps of Engineers
Northwestern Division

News Releases

Record March runoff observed in upper basin; Public meetings set for April 9-11

Northwestern Division
Published April 3, 2019
Observed March runoff above Sioux City was 11 MAF, which set a new record and is nearly 4 times the average March runoff. Releases from all projects are being increased to reflect these conditions.

System storage is 63.2 MAF; 7.1 MAF of the 16.3 MAF of flood control storage is occupied. About 56% of the flood control storage is available to store runoff this spring and summer. Some plains snowpack still remains in areas of North Dakota and South Dakota (upper right graphic). The calendar year runoff forecast, updated on April 1, is 38.2 MAF (151% of average). Observed March runoff above Sioux City was 11 MAF, which set a new record and is nearly 4 times the average March runoff. Releases from all projects are being increased to reflect these conditions.

March runoff in the upper Missouri River Basin above Sioux City, Iowa, was a record 11.0 million acre feet , surpassing the previous record of 7.3 MAF set in 1952. The average March upper basin runoff is 2.9 MAF.

“The record March runoff significantly altered our 2019 upper basin runoff forecast,” said John Remus, chief of the U.S. Army Corps of Engineers Missouri River Basin Water Management Division.

“Our runoff forecast increased to 38.2 MAF, which is 151 percent of normal. The March runoff was nearly 4 times the average. Runoff in the Fort Randall Dam to Gavins Point Dam reach was nearly twice the record highest March runoff. March runoff in the Gavins Point to Sioux City reach was more than that reach typically sees during a year,” said Remus.

The record high runoff in March was caused by 2-4 inches of rain falling on heavy plains snowpack causing the snowpack to rapidly melt on frozen, saturated soils. Pool levels in the four System projects that have significant flood control storage – Fort Peck, Garrison, Oahe and Fort Randall – have all increased significantly to capture much of the runoff. The Corps plans to increase Gavins Point releases to 55,000 cubic feet per second by early next week. Gavins Point releases will be above average for the next several months, and possibly as late as November.

“We need to reduce pool levels in Oahe and Fort Randall over the next several weeks so that those reservoirs are in position to reduce flood risk during the spring and summer. The Fort Peck and Garrison reservoirs are well positioned to receive the runoff from the mountain snowmelt, which typically begins in May,” added Remus.

As of April 1, the mountain snowpack was 97 percent of average in the reach above Fort Peck and 93 percent of average in the reach from Fort Peck to Garrison. Normally the mountain snowpack peaks in mid-April. View the mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.

Much of the plains snowpack in central North Dakota and eastern South Dakota has melted. The heaviest snowpack remains in isolated areas of north central South Dakota and south central North Dakota where the snowpack’s liquid content, or snow water equivalency (SWE), ranges from 1 to 5 inches. Frost depth is still deep in much of the upper basin, including the areas with the remaining snowpack. The Corps is cooperating with other agencies to acquire plains snow measurements in the upper basin.

Based on the March 15 System storage check, flow support for the first half of the navigation season is full service. However, due to above average runoff into Oahe and Fort Randall reservoirs, releases from Gavins Point have been above full service levels to lessen the time that those projects have water stored in their exclusive flood control zones. 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. Flow support is generally sufficient to provide a 9-foot-deep by 300-foot-wide channel.

Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/weeklyupdate.pdf.

The Corps will host six public meetings April 9-11 to discuss the Missouri River Mainstem System, its runoff and reservoir operations. Meeting information is detailed in a separate news release: https://go.usa.gov/xmqSp.

Monthly Water Management Conference Calls

Due to the spring public meetings that will be held April 9-11, the fourth monthly conference call of the 2019 runoff season will be held May 7 to inform basin stakeholders on current weather and runoff forecasts and the planned operation of the System. Presentation materials will be posted on the MRBWM website at: http://www.nwd-mr.usace.army.mil/rcc/. The call is intended for Congressional delegations; Tribes; state, county and local government officials; and the media. It will be recorded in its entirety and made available to the public on the Defense Video and Imagery Distribution System at www.dvidshub.net/unit/usace-nwd.

Reservoir Forecasts

Gavins Point Dam

  • Average releases past month – 30,600 cfs
  • Current release rate – 39,000 cfs
  • Forecast release rate – 55,000 cfs early next week
  • End-of-March reservoir level – 1205.4 feet
  • Forecast end-of-April reservoir level – 1206.0 feet

Fort Randall Dam

  • Average releases past month – 11,600 cfs
  • End-of-March reservoir level – 1366.9 feet (up 16.2 feet from February)
  • Forecast end-of-April reservoir level – 1360.5 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point.

Big Bend Dam

  • Average releases past month – 15,100 cfs
  • Forecast average release rate – 32,100 cfs
  • Forecast reservoir level – 1420.0 feet

Oahe Dam

  • Average releases past month – 9,500 cfs
  • Forecast average release rate – 31,400 cfs
  • End-of-March reservoir level – 1614.7 feet (rising 7.9 feet during March)
  • Forecast end-of-April reservoir level – 1616.0 feet

Garrison Dam

  • Average releases past month – 13,100 cfs
  • Current release rate – 13,000 cfs
  • Forecast average release rate – 13,000 cfs
  • End-of-March reservoir level – 1842.6 feet (rising 5.3 feet during March)
  • Forecast end-of-April reservoir level – 1845.0 feet

Fort Peck Dam

  • Average releases past month – 6,500 cfs
  • Current release rate – 6,500 cfs
  • Forecast average release rate – 6,500 cfs
  • End-of-March reservoir level – 2238.1 feet (up 3.7 feet from February)
  • Forecast end-of-April reservoir level – 2240.1 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.

The six mainstem power plants generated 473 million kWh of electricity in March. Typical energy generation for March is 639 million kWh. The power plants are projected to generate 11.9 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://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf.

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 1967-2018 Average

Change in March

Fort Peck

2238.1

+3.7

15,672

108

+798

Garrison

1842.6

+5.3

19,392

109

+1,703

Oahe

1614.7

+7.9

21,065

119

+2,606

Big Bend

1420.7

+0.1

1,671

98

+2

Fort Randall

1366.9

+16.2

4,489

134

+1,436

Gavins Point

1205.4

-0.4

314

80

-10

 

 

Total

62,603

113

+6,535

 

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

6.9

426

65

Garrison

16.7

1,030

156

Oahe

9.5

583

85

Big Bend

15.1

927

53

Fort Randall

11.6

714

78

Gavins Point

30.6

1,879

36

 

 

Total

473


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

Release no. 19-005