OMAHA, NE – All 2018 stored flood waters were evacuated from the Missouri River mainstem reservoir system (System) as of Jan. 29. The full 16.3 million acre-feet (MAF) of designated flood control storage is available to manage 2019 runoff. “The System stands ready to capture spring runoff, reducing flood risk while providing support to other authorized project purposes. Current Gavins Point releases are 20,000 cubic feet per second (cfs) and will be decreased to 17,000 cfs by mid-February,” said John Remus, Chief of the Corps’ Missouri River Basin Water Management Division.
The latest annual runoff forecast for the Missouri River basin above Sioux City, Iowa is 25.6 MAF, slightly more than the long-term average of 25.3 MAF. Runoff into Fort Peck and Garrison is expected to be below average over the next few months due to the lighter-than-average plains snowpack and below-average mountain snowpack. Runoff in the Sioux City reach is expected to be above average over the next few months as the northern portions of the James River and Big Sioux River basins have widespread and moderate-to-heavy plains snowpack. Portions of those basins contain 4 to 5 inches of estimated liquid content in the snowpack. The remainder of the upper and lower Missouri River basin has light to no snow cover. The Corps is cooperating with other agencies to acquire plains snow measurements in the upper basin.
As of Feb. 4, the mountain snowpack was 88 percent of average in the reach above Fort Peck and 89 percent of average in the reach from Fort Peck to Garrison. Normally, by Feb. 1, 64 percent of the total mountain snowpack accumulation has occurred. Mountain snowpack will continue to accumulate over the next few months and normally peaks in mid-April. View mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.
Current studies indicate 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.
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.
Reservoir Forecasts
Gavins Point Dam
Average releases past month – 23,100 cfs
Current release rate – 20,000 cfs
Forecast release rate – 17,000 cfs by mid-February
End-of-January reservoir level – 1204.2 feet
Forecast end-of-February reservoir level – 1206.0 feet
Notes: Due to scheduled maintenance on the hydropower units, releases may be made from both the powerhouse and spillway.
Fort Randall Dam
Average releases past month – 20,700 cfs
End-of-January reservoir level – 1344.7 feet (up 4.2 feet from December)
Forecast end-of-February reservoir level – 1350.0 feet
Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. Gradually refilled the reservoir to 1350.0 feet allows increased winter hydropower generation at Oahe and Big Bend.
Big Bend Dam
Average releases past month – 23,100 cfs
Forecast average release rate –22,300 cfs
Forecast reservoir level – 1420.0 feet
Oahe Dam
Average releases past month – 24,900 cfs
Forecast average release rate – 22,000 cfs
End-of-January reservoir level – 1605.9 feet (down 1.3 feet from December)
Forecast end-of-February reservoir level – 1606.7 feet
Notes: River ice conditions continue to be monitored below the dam and releases will be adjusted accordingly to minimize flood risk caused by river ice.
Garrison Dam
Average releases past month – 20,200 cfs (ranging from 16,000 cfs to 26,000 cfs)
Current release rate – 26,000 cfs
Forecast average release rate – 26,000 cfs
End-of-January reservoir level – 1838.9 feet (down 0.7 feet from December)
Forecast end-of-February reservoir level – 1837.5 feet
Notes: River ice conditions continue to be monitored below the dam and releases will be adjusted accordingly to minimize flood risk caused by river ice.
Fort Peck Dam
Average releases past month – 11,800 cfs
Forecast average release rate – 12,000 cfs
End-of-January reservoir level – 2235.8 feet (down 1.4 feet from December)
Forecast end-of-February reservoir level – 2234.7 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 804 million kWh of electricity in January. Typical energy generation for January is 708 million kWh. The power plants are projected to generate 9.7 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.