The Missouri River at Omaha could be below flood stage in September, said Jody Farhat of the U.S. Army Corps of Engineers.
Decisions soon to be made will determine whether that happens, she said. Farhat manages the water release rate from the six dams on the upper Missouri.
Corps officials are reviewing eight to 10 scenarios for reducing the record amounts of water now being released from upstream dams. The agency plans to announce by early August when, and by how much, it intends to lower those releases, Farhat said.
Erik Blechinger, a spokesman for the corps, said the agency is weighing competing needs.
"It's kind of a balancing act," he said.
Unusually high mountain snows and unprecedented spring rains in the upper Missouri River basin have caused flooding from Montana to Missouri. In response, the corps began releasing record amounts of water in late May.
In the Omaha-Council Bluffs area, the river has risen to about 6 feet above flood stage, which is 29 feet. Until the river drops substantially, the homes of some 40,000 people are considered at risk if levees were to fail.
Most of those people live in Council Bluffs, where Mayor Tom Hanafan said Thursday that he is prepared for life not returning to normal before winter. Still, he's not apprehensive.
"I'm relatively comfortable with what we've been able to do to maintain our levees," Hanafan said. "It's just the unknowns that are out there . there are weaknesses you can't see."
Blechinger said the scenarios the corps is deciding among include:
» Returning the river to its banks in time for levees to be inspected and for damage to be repaired before next spring. This is an option that also would allow inspection and repair of the spillways and related infrastructure on the dams.
» Lowering river levels even more, so there's less water in the river to form ice jams this winter.
» Sending more water downstream so there is extra space in the reservoirs next year for flood storage. This would require higher releases.
» Getting all six reservoirs low enough that the corps can adjust future water releases in response to heavy rains upstream or downstream. Currently, the four biggest reservoirs are too full for comfort, corps officials say.
Lowering the reservoirs is a clear priority for the corps.
A full reservoir "takes away much of the flexibility in the system," Blechinger said.
The release rate from Gavins Point Dam — the one immediately upstream from Omaha — is at 160,000 cubic feet per second. Before this year the record release rate was 70,000 cfs.
Blechinger said lowering releases to a rate of 40,000 cfs would create near-normal conditions along the river.
"It's the minimum acceptable. It gets water off the levees. But it's still difficult working conditions, because the water is still fairly high," Blechinger said.
The normal wintertime release rate is 20,000 cubic feet per second.
As the corps makes its decision, officials have to consider more than 30 factors, including:
» Timing releases slowly enough that levees dry as the water drops. Too rapid of a drop in river levels could cause the soggy soil on the levees to slough off.
» Lowering river levels fast enough that levees dry out and aren't as susceptible to damage from a wintertime freeze-and-thaw cycle.
» Making enough repairs to levees that communities won't be at risk if next year again brings high snowmelt and rain runoff.
» Taking into account the weather. Fall is a somewhat rainy time of year.
Blechinger said the ultimate decision will be made by Gen. John R. McMahon, commander of the corps' northwestern division. McMahon plans to run his decision past the governors and congressional delegations in the Missouri River basin states.
Any chosen plan is likely to be modified because of the weather, Blechinger said.
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