Corps may dump more water - rains create flooding hazards on Missouri River
Tuesday, June 21, 2011
Continuing rains in Montana and the Dakotas — on top of an already record-level snowpack this past winter — means the U.S. Army Corps of Engineers may have to release even more water through the Upper Missouri River dams before the year is over, Brig. Gen. John McMahon said during a Jefferson City meeting Monday morning.
The Corps, charged by Congress with managing the Missouri River for flood control purposes and other uses, already is releasing water from the Gavins Point Dam at a record 150,000 cubic-feet-persecond (cfs), and expects to keep that release rate going at least through August.
At that 150,000-cfs rate, the Corps predicts the water could rise to around 27 feet at Jefferson City — four feet over flood stage.
Add a lot of rain in the Missouri River Basin system, and the engineers say there could be as much as 35 feet of flooding — 12 feet above flood stage and the second-highest flood onrecord at Jefferson City.
“We have a very dangerous situation on our hands,” McMahon said during the meeting with U.S. Reps. Vicky Hartzler, R-Harrisonville, and Blaine Luetkemeyer, R-St. Elizabeth, Jefferson City and Cole County government officials, representatives of several Mid-Missouri levee districts and a number of area farmers.
“On May 1, we were forecasting a high snowpack, and were creating space in the reservoirs to hold the snow runoff.”
But at that point, the engineering models said it wasn’t too big for the system of six Missouri River dams and reservoirs to handle, McMahon explained, even though the snowpack was deeper than usual.
Until mid-May, that is, when “we had a year’s worth of rain” in about two weeks in eastern Montana, North and South Dakota and Wyoming.
“That basically took all of our flexibility away,” McMahon said, leading to the current plans to release record amounts of water throughout the Missouri River system — for most of the rest of this year.
Adding to the Corps’ problem is geography, he said, since there are no flood control devices available on the Missouri River between the Gavins Point Dam at Yankton, S.D., and the river’s mouth at St. Charles.
And because there are so many variables, McMahon said he couldn’t predict how higher release-levels might affect flood levels along the lower Missouri Basin.
“The greatest threat I see is the very unpredictable rain that could materialize” anywhere downstream from Gavins Point, either along the Missouri itself, or along one of the numerous tributaries — like the Gasconade, Osage, Grand or Kansas Rivers, among others — that feed water into the Missouri, McMahon told the officials’ meeting at Jefferson City’s City Hall.