Something that was unimaginable a few months ago in this year of historic flooding suddenly appears within reach.
Runoff into the Missouri River could approach — even reach — the historic levels set in 2011, Kevin Grode, an engineer with the U.S. Army Corps of Engineers, said Monday.
In the wake of extraordinary rains from north-central Nebraska northward to the Dakotas, the corps has — again — adjusted upward its estimate of how much runoff will pour into the river this year.
The corps is now estimating that 58.8 million acre-feet of runoff will flow into the river, up 4.2 million from its estimate just two weeks ago. An acre-foot is the amount of water that would fill an acre to a depth of one foot.
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As of Friday, runoff had already exceeded the second-highest total set in 1997, according to the corps. The current runoff record, 61 million acre-feet, was set during months-long flooding on the Missouri in 2011.
“There has been rain somewhere in the Missouri River basin each and every day so far in September,” said Kevin Low, a hydrologist with the National Weather Service.
Parts of northern Nebraska, the Dakotas and Montana have seen in excess of 400% of normal rainfall for the month, he said. Many of those areas already have more than exceeded their normal monthly total with two weeks left in September.
In Nebraska, flooding in the north-central part of the state last week washed out roads and culverts. Eight to 10 inches of rain fell in areas like Ainsworth, southeast of Valentine, over two nights.
Because runoff is running so high above and below the dams, the corps is undertaking a balancing act this week in discharges from its lowermost dam.
The agency is cutting back releases from Gavins Point Dam for a few days in the hopes that doing so will prevent flooding of Interstate 29 in western Iowa.
In spite of that effort, the National Weather Service says it’s possible flooding will reach portions of I-29 and I-680 by Wednesday.
Late this week, the corps will significantly increase releases to 80,000 cubic feet per second. Releases will likely stay at that level well into October, said John Remus of the corps.
High flows along the river are expected to send more water through some areas where levees are broken. The corps is sending teams out to monitor levees, and it’s doing what it can to protect levee repairs that remain fragile.
Corps officials say they don’t anticipate more damage to homes and community, but added that in the abundance of caution, people behind damaged levees need to pay attention to water levels and changing conditions.
On Monday, Iowa officials warned residents in southwest Mills County who live west of I-29 and south of Lambert Avenue to stay alert and be prepared to evacuate if water starts to rise. Water could flow through a levee breach into an area already saturated with water, Mills County spokeswoman Sheri Bowen said in a release.