OMAHA, Nebraska --
Releases reductions from Missouri River mainstem dams will begin Wednesday, Nov. 20 at Garrison Dam. Release reductions are also scheduled for Friday, Nov. 22 at Fort Randall Dam and Saturday, Nov. 23 at Gavins Point Dam.
Inflows into reservoirs at Fort Randall and Gavins Point Dams since Nov. 1 have been lower than forecast, and the reservoir elevation at Garrison Dam is declining faster than forecast meaning Missouri River Mainstem System storage is declining faster than planned.
Even with the planned release reductions, System storage is expected to be 57.4 million acre feet by Nov. 30, approximately 0.3 MAF lower than was projected in the Nov. 1 forecast.
Maintaining releases at 80,000 cubic feet per second from the system would result in a pool elevation at Fort Randall Dam that would potentially impact water supply. Ensuring access for water supply would require increased upstream releases, primarily from the Oahe reservoir, which would cause flooding to critical infrastructure immediately downstream.
“To avoid impacts to water supply and risks to critical infrastructure downstream of Oahe Dam, changes to system releases are aimed at slowing the pool decline of the Fort Randall reservoir,” said John Remus, chief of the Missouri River Water Management Division.
The release reduction schedule from Garrison, Fort Randall and Gavins Point Dams are as follows:
- Garrison Dam: Beginning Nov. 20, releases will decline by 3,000 cfs each day to a target rate of 24,000 cfs on Nov. 27.
- Fort Randall Dam: Beginning Nov. 22, releases will be incrementally decreased to a target of 66,000 cfs by Nov. 26 and further reductions to reach 46,000 cfs by Dec. 6.
- Gavins Point Dam: Beginning Nov. 23, releases decrease to 75,000 cfs, then on Nov. 27 to 70,000 cfs with daily reductions from Dec. 3 to reach 54,000 cfs by Dec. 6.
The complete three-week forecast is available at, http://go.usa.gov/xUEh5, and is updated each Wednesday, or more frequently if needed.
“Overall releases from the Missouri River system will still be higher than normal through the winter to ensure flood control zones are emptied before the next runoff season. We are continuing to monitor conditions and will make adjustments as necessary” said Remus.
Release reductions are also geared toward lowering river stages in areas where the Missouri River ices over. River ice conditions can be tracked here, https://go.usa.gov/xpZZX.
“The river in the Bismarck area can rise as much as 6 feet during ice-in which means the river stage needs to be lower to prevent flooding during this time. Once the ice has formed, then releases can be gradually increased to smooth the underside of the ice and carry a little more water. Trying to push more water under the ice or dropping releases too much can cause the ice to break up and jam,” said Remus.
The National Weather Service issues official stage forecasts for the Missouri River and the public should monitor their nearest upstream gage as fluctuations to river stages will occur with regional precipitation along the rivers and creeks that join the Missouri River downstream from Gavins Point Dam. More information about releases and river stages downstream from Gavins Point Dam is available here http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/GRFT.pdf and from the National Weather Service, Missouri Basin River Forecast Center https://www.weather.gov/mbrfc/.
The average November system release from Gavins Point Dam is 31,400 cfs.
Additional, historical project data including pool elevations, inflows and releases, is available in the Project Statistics section here: https://www.nwd.usace.army.mil/MRWM/Statistics/.