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Posted 11/5/2018

Release no. 18-116

Eileen Williamson

OMAHA, NE - Higher-than-average releases from all Missouri River Mainstem System projects, including Gavins Point, will continue through November. “Gavins Point releases will remain near 58,000 cubic feet per second (cfs) for the remainder of the navigation season. To ensure all stored 2018 runoff is evacuated prior to the 2019 runoff season, most of the releases must occur before the river ices over in reaches predominantly upstream from Lake Oahe,” said John Remus, Chief of the U.S. Army Corps of Engineers Missouri River Basin Water Management Division.

The 2018 runoff forecast in the Missouri River Basin above Sioux City, Iowa is 41.4 million acre feet (MAF), 163 percent of average. If this forecast is realized, the 41.4 MAF of runoff will be third highest runoff in 120 years of record-keeping (1898-2017), exceeded only in 1997 and 2011.

The October runoff summation above Sioux City was 1.9 MAF, 160 percent of average. Due to heavy September and October rainfall, the total two-month runoff in the unregulated reach from Gavins Point Dam to Sioux City was 1.7 MAF, which is the highest September-October runoff in 120 years of record-keeping.

The Missouri River Mainstem reservoir system storage was 59.6 MAF as of November 1, occupying 3.5 MAF of the 16.3 MAF flood control zone. “System storage declined 2.6 MAF in October and will continue to gradually decline in November,” said Remus. System storage peaked on July 8 at 68.4 MAF, occupying 12.3 MAF of the designated 16.3 MAF of flood control storage. “Reservoir releases will be adjusted as necessary to provide downstream flood risk reduction and continue evacuation of stored flood water,” said Remus. It is important to note that 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.

Based on the September 1 System storage, winter releases from Gavins Point will be at least 17,000 cfs. Based on the latest reservoir studies, there will be a 10-day extension to navigation flow support and a Gavins Point winter release of 20,000 cfs. Releases from Gavins Point will be reduced to near 50,000 cfs in late November before being reduced 3,000 cfs per day until reaching the winter release rate around December 11. Navigation flow support at the mouth of the Missouri River will end on December 11.

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 and river conditions and will adjust System regulation based on the most up-to-date information.

The 2018-2019 draft Annual Operating Plan for the Missouri River Mainstem System was posted in September at: http://www.nwd.usace.army.mil/MRWM/Public-Meetings/. Fall public meetings will be held in six cities throughout the basin in early November. These meetings will include a presentation regarding 2018 operations and plans for regulating the reservoir system in 2019, followed by a question and answer session. The public meetings will be conducted at the times and locations listed below.

 Tuesday, Nov. 6 Wednesday, Nov. 7   Friday, Nov. 9 

Fort Peck, MT

  • Start time:  11 a.m. (MST)
  • Fort Peck Interpretative Center
  • Lower Yellowstone Rd.

Pierre, SD

  • Start time:  10 a.m. (CST)
  • Casey Tibbs Conference Center
  • 210 Verendrye Drive, Ft. Pierre, SD

Smithville, MO

  • Start time:  11 a.m. (CST)
  • Paradise Point Golf Course
  • 18212 Golf Course Rd

Bismarck, ND

  • Start time:  6 p.m. (CST)
  • Bismarck State College, NECE Bldg.15, Rm 304
  • 1200 Schafer Street, Bismarck ND

Sioux City, IA

  • Start time:  4 p.m. (CST)
  • Stoney Creek Hotel & Conference Center
  • 300 3rd St.

Nebraska City, NE

  • Start time:  4 p.m. (CST)
  • Lewis and Clark Interpretive Center
  • 100 Valmont Drive

Reservoir Forecasts

  • Gavins Point Dam releases averaged 56,200 cfs during October. Releases will remain near 58,000 cfs, downstream conditions permitting, until late November when releases will be reduced to 50,000 cfs. In early December, releases will begin to decrease by 3,000 cfs per day until the winter release rate of 20,000 cfs is reached around December 11.
  • Fort Randall Dam releases averaged 52,300 cfs in October. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. Releases are being made from both the powerhouse and outlet tunnels. The reservoir level was at 1346.4 feet at the end of October, falling 6.2 feet during the month. The reservoir level will gradually decline to near 1337.5 feet during November. The reservoir level is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend.
  • Big Bend Dam releases averaged 42,500 cfs in October. Releases are expected to average 44,500 cfs and the reservoir will remain near is normal elevation of 1420.0 feet during November.
  • Oahe Dam releases averaged 45,900 cfs during October. Releases are expected to average 44,000 cfs in November. Releases will continue to be made from both the powerhouse and the outlet tunnels. Releases from the outlet tunnels are required due to scheduled maintenance on the hydropower units and the need to continue evacuating stored runoff. The reservoir level was 1610.6 feet at the end of October, decreasing 3.4 feet during the month. Reservoir levels will continue to decline during November with a projected end-of-month elevation near 1607.7 feet.
  • Garrison Dam releases averaged 29,300 in October and will remain near 29,000 cfs during November. The reservoir level was 1841.8 feet at the end of October, a reduction of 1.8 feet from the end of September. The reservoir level is expected to continue declining through November and be near elevation 1840.3 feet at the end of the month.
  • Fort Peck Dam releases averaged 11,800 cfs during October. Releases are expected to average near 12,000 cfs during November. Due to scheduled maintenance on the hydropower units, releases are currently being made through the powerhouse and spillway. The reservoir level was 2239.9 feet at the end of October, declining 1.4 feet during the month. The reservoir level is expected to continue declining through November and be near elevation 2238.3 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 1,182 million kWh of electricity in October. Typical energy generation for October is 811 million kWh. The power plants are projected to generate 12.5 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.




Pool Elevation
(feet above mean sea level)

Water in Storage
(1,000 acre-feet)


On October 31

Change in October

On October 31

% of 1967-2017 Average

Change in October

Fort Peck


















Big Bend






Fort Randall






Gavins Point
















Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck












Big Bend




Fort Randall




Gavins Point