The 2018 runoff forecast in the Missouri River Basin above Sioux City, Iowa, is 30.2 million acre feet (MAF), 119 percent of average according to the Corps. “The updated forecast increased slightly from last month due to the continued accumulation of mountain and plains snowpack in the upper basin,” said John Remus, Chief of the Missouri River Basin Water Management Division. “Based on the current plains and mountain snowpack and precipitation outlooks, runoff into the Fort Peck and Garrison reservoirs is expected to be above average from March through August,” said Remus. For comparison, the 2017 runoff was 29.6 MAF, 117 percent of average.

As of April 1, the mountain snowpack was 127 percent of average in the reach above Fort Peck and 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.
Plains snowpack is currently heaviest in central and eastern Montana. The snowpack’s liquid content, or snow water equivalency (SWE), ranges from 2 to 8 inches in localized areas. The remaining areas of the upper basin have much less plains snowpack, ranging from trace amounts to 3 inches of SWE. The Corps is cooperating with other agencies to acquire plains snow measurements in the upper basin.

The Missouri River mainstem reservoir system (System) began the 2018 runoff season at the base of the annual flood control pool, providing the full 16.3 MAF of flood control storage to capture runoff. System storage was 58.3 MAF as of April 1, occupying 2.2 MAF of the 16.3 MAF flood control zone. “More than 85 percent of the System’s flood storage remains available to capture runoff from the remaining plains snowpack and spring rainfall as well as the runoff from the mountain snowmelt,” said Remus.” 

In mid-March, Gavins Point releases were increased from 20,000 to 24,000 cubic feet per second (cfs) in support of the Missouri River navigation season which began April 1 near St. Louis, Mo. “Because of the higher than average runoff forecast, the service level was increased 10,000 cfs above full service to provide beneficial use of the excess runoff while reducing flood risk,” said Remus. Although the service level was increased, releases from Gavins Point ranged from 22,000 to 24,000 cfs during late March to reduce flood risk along the lower Missouri River while flows in tributaries downstream of Gavins Point remained high.

As tributary flows recede, releases from Gavins Point will be increased until they reach the expanded navigation support levels. Gavins Point releases will be adjusted, if needed, in response to basin conditions. When necessary, the Corps will reduce releases from the System projects and utilize the available flood control space in the reservoirs, in order to lessen downstream river levels; however, the ability to significantly reduce flood risk along the lower Missouri River diminishes at locations further downstream due to the large uncontrolled drainage area and the travel time from Gavins Point Dam.
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 continue to monitor basin conditions, river ice conditions, and plains and mountain snow accumulation, and will adjust the regulation of the System based on the most up-to-date information.

Spring Public Meetings
Meeting times and locations are listed below.

• Tuesday, April 17 – Smithville, MO
• Start time: 10 a.m. (CDT)
• Jerry Litton Visitor Center
• 16311 DD Hwy

• Tuesday, April 17 – Omaha, NE
• Start time: 4 p.m. (CDT)
• Nebraska Regulatory Office
• 8901 South 154th St.

• Wednesday, April 18 – Pierre, SD
• Start time: 10 a.m. (CDT)
• Ramkota Hotel
• 920 W Sioux Ave.

• Wednesday, April 18 – Bismarck, ND
• Start time: 6 p.m. (CDT)
• Bismarck State College, National Energy Center of Excellence (NECE), Bldg. 15, Rm 335
• 1200 Schafer Street

• Thursday, April 19 – Fort Peck, MT
• Start time: 10 a.m. (MDT)
• Fort Peck State Fish Hatchery
• 277 Montana Highway 117

Reservoir Forecasts

Gavins Point Dam releases averaged 21,500 cfs during March. Releases began increasing by 2,000 cfs per day beginning on March 31, and will continue to be increased until they reach the expanded navigation support levels, which are estimated at 34,000 to 36,000 cfs. The Gavins Point reservoir ended March at elevation 1206.6 feet and will remain near 1206.0 feet during April.

Fort Randall Dam releases averaged 16,000 cfs in March. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. Due to on-going maintenance at the project, planned releases will require releases from the powerhouse and outlet tunnels. The reservoir ended March at elevation 1357.1.5 feet, rising 8.2 feet during April. The reservoir will gradually fall to near 1355.2 feet during April.

Big Bend Dam releases averaged 19,600 cfs in March. Releases are expected to average 25,300 cfs during April. The reservoir will remain near its normal elevation of 1420.0 feet during April.

Oahe Dam releases averaged 21,000 cfs during March. Releases are expected to average 24,600 cfs in April. Planned releases will primarily be through the powerhouse, however, outlet tunnels may be used this spring during powerhouse maintenance. The reservoir ended March at elevation 1609.1 feet, rising 1.3 feet during April. The reservoir level is expected to rise 1.7 feet during April.

Garrison Dam releases averaged 22,400 cfs during March. Releases will be gradually increased to 28,000 cfs during April. Garrison reservoir ended March at elevation 1839.0 feet, rising 1.2 feet during the month. The reservoir level is expected to rise 0.8 foot during April, ending the month near elevation 1839.8 feet.

Fort Peck Dam releases averaged 8,300 cfs during March. Releases were increased to 9,000 cfs on March 29 and will remain at that rate during April. The reservoir ended March at elevation 2236.0 feet, rising 2.1 feet during the month. The reservoir is expected to rise 1.6 feet during April ending the month near elevation 2237.6 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 697 million kWh of electricity in March. Typical energy generation for March is 641 million kWh. The power plants are projected to generate 11.5 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

WATER RELEASES AND ENERGY GENERATION FOR MARCH