The U.S. Army Corps of Engineers Missouri River Basin Water Management Division is increasing releases at the four lower dams on the Missouri River following heavy rains in August.
The higher releases will evacuate flood water stored in the mainstream reservoir system, lessening potential of future flood risk, officials said. The excess water will also allow the Corps to extend the navigation season 10 days and provide higher winter releases, which will benefit winter hydropower generation and reduce risks to water intakes during periods of ice formation.
Runoff above Sioux City, Iowa, in August was 3.2 million acre feet, 241 percent of normal. The 2014 runoff forecast is 35.6 million acre feet, 141 percent of normal. Average annual runoff is 25.2 million acre feet.
Based on the Sept. 1 reservoir system storage, there will be a one-day extension to the navigation season with Gavins Point winter releases of 20,000 cubic feet per second. Navigation service at the mouth of the Missouri River will now end Dec. 10.