US Army Corps of Engineers
Northwestern Division

News Releases

Widespread rainfall leads to continued high runoff; Gavins Point releases to remain at high levels for the summer and fall

Northwestern Division
Published June 5, 2019
Updated: June 6, 2019
The 3-week forecast for Fort Randall, Gavins Point and the Missouri River Mainstem System Forecast shows pool levels and forecast inflows and releases.

The 3-week forecast for Fort Randall, Gavins Point and the Missouri River Mainstem System Forecast shows pool levels and forecast inflows and releases.

Three week forecast for Fort Peck, Garrison, and Oahe dams on the Missouri River. Charts show forecast pool levels, inflows and releases.

Three week forecast for Fort Peck, Garrison, and Oahe dams on the Missouri River. Charts show forecast pool levels, inflows and releases.

The six dams on the main stem of the Missouri River capture runoff from Wyoming, Montana, and North Dakota, South Dakota and north central Nebraska. Upper Basin Missouri River system runoff is measured upstream of Sioux City, Iowa.

The six dams on the main stem of the Missouri River capture runoff from Wyoming, Montana, and North Dakota, South Dakota and north central Nebraska. Upper Basin Missouri River system runoff is measured upstream of Sioux City, Iowa.

The Missouri River Water Management office releases a report at the beginning of each month to the public documenting the monthly river forecast and release schedule. The Missouri River Water Management Division is part of the Northwestern Division of the U.S. Army Corps of Engineers and is located in Omaha, Nebraska.

The Missouri River Water Management office releases a report at the beginning of each month to the public documenting the monthly river forecast and release schedule. The Missouri River Water Management Division is part of the Northwestern Division of the U.S. Army Corps of Engineers and is located in Omaha, Nebraska.

**Correction: Average May runoff is 3.3 MAF. It was originally reported as 5.6 MAF. **

Much-above average runoff in the upper Missouri River basin (above Sioux City, Iowa) extended into May following widespread and heavy rainfall in South Dakota and Nebraska. Additionally, widespread and heavy rainfall in the lower basin, particularly in Kansas, has led to large tributary and Missouri River flows downstream of the six main stem reservoirs on the Missouri River.

May runoff in the upper basin was 8.9 million acre feet (MAF), which is 267 percent of average.  The average May runoff is 3.3 MAF. May runoff was the second highest on record, only surpassed by 2011’s 9.2 MAF. Runoff in the Fort Randall Dam to Gavins Point Dam reach was 1.4 MAF, which is more than the average annual runoff for that reach.

The high May runoff increased the 2019 upper basin runoff forecast to 50.0 million acre-feet (MAF). If realized, this runoff total would be the second highest runoff in 121 years of record-keeping, only surpassed by 2011 (61.0 MAF) and exceeding the 49.0 MAF observed in 1997. Runoff in 2018 was 42.1 MAF, which is currently third highest.

“System releases from Gavins Point Dam are currently 75,000 cfs, which is more than twice the average release for this time of the year. We will maintain Gavins Point releases at this rate to continue evacuating water from Oahe and Fort Randall, which have used much of their respective flood storage,” said John Remus, chief of the U.S. Army Corps of Engineers Missouri River Basin Water Management Division.

Oahe and Fort Randall are currently in their respective exclusive flood control zones. Fort Peck and Garrison are expected to enter their exclusive flood control zones during June as the remaining mountain snowpack melts. As a result of the high reservoir levels, the Corps expects that releases from all System projects will be above average for the next several months, and possibly as late as November.

The Corps has been coordinating with the U.S. Bureau of Reclamation (USBR) regarding the USBR projects in Montana and Wyoming with designated flood control storage. Releases from several of the USBR projects are being adjusted, and flood control storage is being used.  This measure provides additional ability to manage the pools at all the mainstem reservoirs during June and July.

The mountain snowpack peaked in both reaches: on April 18 in the Fort Peck reach at 105%of average and on April 17 in the Fort Peck to Garrison reach at 104% of average. Normally the mountain snowpack peaks in mid-April. Cooler temperatures and additional snow in the mountains has slowed the melt, especially in the Fort Peck to Garrison reach. As of June 4, 34% of this year’s peak remains in the Fort Peck reach and 56% of this year’s peak remains in the Fort Peck to Garrison reach.

“Fort Peck and Garrison reservoir levels are positioned to ensure that there is adequate flood control space to capture and manage the mountain snowmelt runoff,” added Remus. View the mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.

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 in the upper basin, releases from Gavins Point have been above full service levels to reduce the occupied flood storage at Oahe and Fort Randall. Based on the June 1 service level check, the service level was increased from 55,000 to 70,000 cfs, which is 35,000 cfs above the full service level of 35,000 cfs.

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 Basin Update as well as forecast information from partner agencies is available through the Missouri Basin Web app at http://go.usa.gov/xE6fC.

Monthly Water Management Conference Calls

Due to the ongoing flooding in the lower basin, the monthly water management calls are being reformatted.  The calls will be held weekly, and will include a briefing from the National Weather Service’s Missouri Basin River Forecast Center, an updated on the Missouri River mainstem reservoir system operations, and updates on the ongoing and planned flood recovery efforts in both the Omaha and Kansas City Districts. The first of these calls will be held Thursday, June 6. The call is intended for Congressional delegations; Tribes; state, county and local government officials, levee and drainage districts; 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 – 57,400 cfs
    • Current release rate – 75,000 cfs
    • Forecast release rate – 75,000 cfs
    • End-of-May reservoir level – 1207.6 feet
    • Forecast end-of-June reservoir level – 1206.0 feet
  • Fort Randall Dam
    • Average releases past month – 47,800 cfs
    • End-of-May reservoir level – 1370.2 feet (up 6.7 feet from April)
    • Forecast end-of-May reservoir level – 1370.2 feet
    • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point.
  • Big Bend Dam
    • Average releases past month – 41,300 cfs
    • Forecast average release rate – 47,600 cfs
    • Forecast reservoir level – 1420.0 feet
  • Oahe Dam
    • Average releases past month – 35,900 cfs
    • Forecast average release rate – 47,000 cfs
    • End-of-May reservoir level – 1618.8 feet (rising 2.4 feet during May)
    • Forecast end-of-June reservoir level – 1617.0 feet
  • Garrison Dam
    • Average releases past month – 23,500 cfs
    • Current release rate – 15,000 cfs
    • Forecast average release rate – 46,000 cfs (late June)
    • End-of-May reservoir level – 1847.8 feet (rising 1.4 feet during May)
    • Forecast end-of-June reservoir level – 1851.8 feet
    • Notes: Releases will be stepped up from 15,000 cfs to 46,000 cfs during June.
  • Fort Peck Dam
    • Average releases past month – 8,200 cfs
    • Current release rate – 9,000 cfs
    • Forecast average release rate – 15,000 cfs (late June)
    • End-of-May reservoir level – 2243.8 feet (up 3.2 feet from April)
    • Forecast end-of-June reservoir level – 2247.4 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 1025 million kWh of electricity in May. Typical energy generation for May is 790 million kWh. The power plants are projected to generate 13.3 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 May 31

Change in May

On May 31

% of 1967-2018 Average

Change in May

Fort Peck

2243.8

+3.2

16,968

117

+728

Garrison

1847.8

+1.4

21,153

119

+499

Oahe

1618.8

+2.4

22,426

127

+756

Big Bend

1420.6

+0.1

1,662

97

0

Fort Randall

1370.2

+6.7

4,813

144

+642

Gavins Point

1207.6

+1.5

366

93

+38

 

 

Total

67,388

122

+2,663

 

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

8.2

506

86

Garrison

23.5

1,443

231

Oahe

35.9

2,205

344

Big Bend

41.3

2,541

91

Fort Randall

47.8

2,938

223

Gavins Point

57.4

3,527

50

 

 

Total

794

 


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

Release no. 19-042