Farmers who live and work along the Missouri River got some good news recently. In late July, U.S. Army Corps of Engineers Northwestern Division commander, Brig. Gen. John McMahon, announced plans to gradually reduce water releases from the dams on the river, beginning this month.
Gradual decreases began on Aug. 1, when releases from the southernmost dam on the river at Gavin's Point were reduced to 150,000 cubic feet per second (cuffs). Gavins Point Dam has been releasing a record 160,000 cfs since early summer, causing major flooding downstream to roadways, farms and fields.
Corps of Engineers officials said in a news release that release levels from Gavins Point Dam will be stepped down 5,000 cfs daily beginning in mid-August, reaching 90,000 cfs around Aug. 27. Releases will stay at 90,000 cfs, which is still well above the previous release record of 70,000 cfs set in 1997, for approximately two weeks. Then, releases will drop 5,000 cfs every two days until reaching 40,000 cfs in late September, slightly above normal fall release levels.
"This plan allows the Corps to evacuate flood water from the reservoir system in a responsible way to prepare for the 2012 runoff season, while reducing the risk of further damages," said McMahon. It gets affected homeowners, farmers and businesses back on their properties to begin repair and recovery as quickly as possible, he said.
Last week, dams at Garrison and Oahe reached 85,000 cfs, in order to get water back within the former river channel and to begin floodplain drainage along the river at Bismarck and Pierre.
The Corps of Engineers said that this plan will allow for inspection and repair of levees and other infrastructure in the drainage areas and will ensure adequate storage for the 2012 runoff season.
"We have already seen water inflows to the system decline and empty system flood control space increase in the past three weeks," said McMahon. "We are confident that this plan will best prepare us for the 2012 runoff season."
Holding releases from Gavins Point steady at 150,000 cfs through mid-August allows Fort Peck, Garrison and Oahe dams to move out of exclusive flood control storage, and it provides operational flexibility for the Corps to respond if significant rainfall occurs.
"It's important that we drawdown these releases with full consideration of the many risks that remain," McMahon said. "A rapid drawdown with high flows could cause extensive bank erosion and slumping in the levees, while too slow of a drawdown could leave high water on temporary and permanent levees, dams and other critical infrastructure, further increasing risks for overtopping and breaches."
The current 2012 weather forecast predicts a 66.6% chance of normal or below normal precipitation, and a 33.3% chance of wetter than normal conditions. Fall of 2011 is forecasted to be wetter than normal, according to Corps officials, and these predictions contributed to the release scheduling plan.
In the news release, the Corps of Engineers said that there is a low probability of the re-occurrence of the 2011 runoff, because it is considered a 500-year event. This past year was the highest runoff season in the 113-year history of the Corps of Engineers keeping records on the Missouri River Basin.
For more information on current release plans and daily forecasted reservoir and river information, visit the water management section on the Northwestern Division U.S. Army Corps of Engineers website at http://www.nwd-mr.usace.army.mil/rcc.