US Army Corps of Engineers
Northwestern Division

News Releases

System preparations for 2019 runoff season continue

Published Jan. 8, 2019
For Yankton and Sioux Falls, South Dakota, 2018 is the wettest year on record. The Big Sioux, Elkhorn, Floyd, James, and Niobrara rivers and the Missouri River downstream from Gavins Point Dam -- where flows are unregulated by dams -- saw annual precipitation 8 to 20 inches above normal. Image Courtesy National Weather Service water.weather.gov.

For Yankton and Sioux Falls, South Dakota, 2018 is the wettest year on record. The Big Sioux, Elkhorn, Floyd, James, and Niobrara rivers and the Missouri River downstream from Gavins Point Dam -- where flows are unregulated by dams -- saw annual precipitation 8 to 20 inches above normal. Image Courtesy National Weather Service water.weather.gov.

The Missouri River, while not frozen over completely, has ice forming on the shore.

The Missouri River, while not frozen over completely, has ice forming on the shore. Releases from Garrison Dam have been reduced to 16,000 cfs and will remain near that rate to prepare for possible river freeze-in at Bismarck. River stages rise rapidly during ice in, which is why releases are reduced. The Bismarck gage rose 5 feet on December 30. Once an ice cover is established, releases can be gradually increased. This year, they will likely increase to 26,000 cfs.

OMAHA, NE – The U.S. Army Corps of Engineers (Corps) continues to prepare the Missouri River Mainstem System (System) for the 2019 runoff season. Current Gavins Point releases are 20,000 cubic feet per second (cfs). Gavins Point releases will be increased to 24,000 cfs this week.

“The higher-than-average winter releases from Gavins Point will continue the evacuation of the stored flood waters from the 2018 runoff season,” said John Remus, Chief of the Corps’ Missouri River Basin Water Management Division. “These releases will provide additional hydropower generation during the winter, which is one of the peak power demand periods. In addition, the higher-than-average releases will benefit municipal and industrial water intakes below Gavins Point Dam, which can be impacted by low water levels during periods of ice formation,” added Remus. Gavins Point Dam winter releases normally range between 12,000 and 17,000 cfs.

The 2018 calendar year runoff was 41.9 million acre feet (MAF), the third highest runoff in 120 years of record-keeping (1898-2017), exceeded only in 1997 and 2011. As of Jan. 6, the total volume of water stored in the System is 56.6 million acre feet (MAF), occupying 0.5 MAF of the 16.3 MAF combined flood control storage zones. Based on current soil moisture conditions, current plains and mountain snowpack, and long-term temperature and precipitation outlooks, the 2019 calendar year runoff forecast is 25.7 MAF above Sioux City, Iowa, 101 percent of average. Average annual runoff is 25.3 MAF. The runoff forecast will be updated on a monthly basis, and more often if warranted, throughout 2019.

Current studies indicate that flow support for Missouri River navigation will be at full service levels for the first half of the 2019 season, which begins on April 1 at the mouth. The actual service level will be based on the total volume of water stored in the System on March 15, in accordance with the guidelines in the Master Manual. 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.

River ice conditions below all System projects will be closely monitored throughout the winter season. The Corps will also continue to monitor basin and river conditions, including plains and mountain snow accumulation, and will adjust System regulation based on the most up-to-date information. The mountain snowpack accumulation period is underway. Mountain snowpack is currently below average in both reaches; however, the mountain snowpack accumulation period is less than 50 percent complete. The mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.

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.

Final 2018-2019 Annual Operating Plan Released
After reviewing comments received on the draft, the Missouri River Basin Water Management Division developed and released the Final Annual Operating Plan for the Missouri River Basin for 2018–2019. The plan is posted at https://www.nwd.usace.army.mil/MRWM/Public-Meetings/.

Reservoir Forecasts

  • Gavins Point Dam releases averaged 25,600 cfs during December. Releases are currently 20,000 cfs and will be increased to 24,000 cfs in early January. Due to scheduled maintenance on the hydropower units, releases will be made from both the powerhouse and spillway. The Gavins Point reservoir ended December at elevation 1205.7 feet and will be near 1207.5 feet during the winter months.
  • Fort Randall Dam releases averaged 21,400 cfs in December. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The reservoir level was at 1340.1 feet at the end of December, rising 3.1 feet during the month. The reservoir will gradually be refilled during the winter to increase winter hydropower generation at Oahe and Big Bend.
  • Big Bend Dam releases averaged 19,800 cfs in December. Releases are expected to average 25,400 cfs and the reservoir will remain near is normal elevation of 1420.0 feet during January.
  • Oahe Dam releases averaged 22,000 cfs during December. Releases are expected to average 24,800 cfs in January. The reservoir ended December at elevation 1607.2 feet, remaining steady during the month. The reservoir level is expected to decline approximately another 0.3 foot during January.
  • Garrison Dam releases averaged 20,500 in December. Releases are currently 16,000 cfs and will remain near that rate to prepare for possible river freeze-in at Bismarck. Once an ice cover is established, releases will be gradually increased to 26,000 cfs. The reservoir level was 1839.6 feet at the end of December, a reduction of 0.6 foot during the month. The reservoir level is expected to continue declining through January and be near elevation 1838.7 feet at the end of the month.
  • Fort Peck Dam releases averaged 11,600 cfs during December. Releases will remain near 12,500 cfs during January. The reservoir level was 2237.2 feet at the end of December, declining 1.4 feet during the month. The reservoir level is expected to continue declining through January and be near elevation 2235.9 feet at the end of the month.

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 758 million kWh of electricity in December. Typical energy generation for December is 684 million kWh. The power plants are projected to generate 12.3 billion kWh of electricity this year, compared to the long-term average of 9.3 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 December 31

Change in December

On December 31

% of 1967-2017 Average

Change in December

Fort Peck

2237.2

-1.4

15,485

107

-301

Garrison

1839.6

-0.6

18,411

104

-182

Oahe

1607.2

0.0

18,567

105

-1

Big Bend

1420.7

+0.4

1,671

98

+24

Fort Randall

1340.5

+3.1

2,361

71

+174

Gavins Point

1205.7

-1.1

320

81

-27

 

 

Total

56,815

103

-313

 

WATER RELEASES AND ENERGY GENERATION FOR DECEMBER

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

11.6

715

120

Garrison

20.5

1,259

193

Oahe

22.0

1,350

199

Big Bend

19.8

1,216

76

Fort Randall

21.4

1,314

113

Gavins Point

25.6

1,573

57

 

 

Total

758


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