The U.S. Army Corps of Engineers, which is still sending above-normal releases from its six Missouri River dams, does not plan to increase its flood storage capacity this fall and winter because of risks to downstream levees.
Brig. Gen. John R. McMahon, commander of the Corps’ Northwest Division, says the planned release schedule announced July 29 will allow the Corps to get its system ready for the 2012 season when it starts March 1.
“We came to the conclusion that this year we would not need additional flood control space,” he says.
That came after considering several factors, including peoples’ need to return to flooded homes, farms and businesses; weather forecasts for this fall and winter; risks from continued high water on saturated levees; the need to inspect and repair dams and damaged infrastructure, and the need to release water in Kansas reservoirs.
Record snowfall and rain in May created runoff that peaked at 72.8 million acre-feet in a system that was designed to handle 40 MAF, McMahon says.
The planned step-down Missouri releases will ease river flow. At Gavins Point Dam, near Yankton, S.D., the release dropped from a record 160,000 cubic ft per second — a rate held since June 24 — to 155,000 cfs July 30 and 150,000 cfs Aug. 1. It will fall to 40,000 cfs Sept. 30 and 20,000 cfs Dec. 1.
The other dams, all upstream, have already started reducing releases.
Based on that schedule, the Missouri should be back in its banks by mid-September at Omaha and late September or early October at Rulo, Neb., says John Remus, Omaha District chief of the hydrologic engineering branch.
“It took a month to fill the flood plain, and will take at least that long to drain it,” McMahon says.
The risk to levees continues as long as water is high, he says.