Reservoir system prepared for 2019 runoff season

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.

Reservoir Forecasts:

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.

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.

 

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.

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.