Conditions ripe for Missouri River flooding in 2020

U.S. Army Corps of Engineers officials said they don't want to alarm everyone, but current conditions and weather forecasts point to a good chance that the river will run high again next year.

"We're looking at a higher probability of increased runoff. People need to be aware of the increased chances of flooding," John Remus, chief of the U.S. Army Corps of Engineers' Missouri River Water Management Division in Omaha, told an audience of about 125 people Wednesday evening at the corps' Missouri River Basin water management meeting at Sioux City's Betty Strong Encounter Center.

Just how the corps intends to deal with the expected wet conditions was asked of Remus more than once.

[Corps of Engineers official: Missouri River flood control measures need to be changed.]

Will the corps evacuate more water than usual during the winter or early spring from the river's six reservoirs to leave more room to catch spring runoff from snowmelt and rainfall?

Remus said the corps still must evacuate this year's water by March 1 in hopes of getting to a base storage level of 56.1 million acre-feet. It's unlikely that storage levels will be dropped lower than that, he said, but if conditions are right, the corps might push more water than normal through dams earlier in the year.

"If we have the opportunity to get more water out early next year, we will," Remus said. "We will be as aggressive as we can."

Corps officials showed the audience a series of maps and graphs that showed above-average rainfall this year across most of the Missouri River basin. South Dakota alone has experienced its wettest 12-month period in 121 years of record keeping. Other states aren't far behind. All that rain has left soil 99 percent saturated across much of the region.

"It doesn't get any greener than this," Kevin Grode, team leader of the corps' Reservoir Regulation Division, said, pointing to a map that showed, in varying shades of green, the soil moisture percentage.

The corps has forecast 2019 runoff to hit 61 MAF, which would tie 2011 for the highest runoff total in 121 years of record keeping. The annual average is 25.3 MAF.

The currently saturated soil won't soak up much of that runoff, leading to forecasts of runoff levels at twice the average amount through the remainder of the year. Soils are expected to be near their moisture capacity when they freeze this winter, leaving little ability to soak up water once the ground thaws in the spring.

Making matters worse is a National Weather Service forecast that shows a better-than-average chance of above-average precipitation from November through January.

[Read more: Missouri River will remain at high level into December.]

For now, the corps is focused on evacuating the 2019 runoff. Releases from Gavins Point Dam near Yankton, South Dakota, have been at 80,000 cubic feet per second -- more than twice the average rate for this time of year -- since September. Releases are expected to remain at that level until Dec. 1, when the corps will begin reducing them to 22,000 cfs for the winter by Dec. 15. If warmer weather persists into December, releases could remain higher for a little longer to evacuate more water. Normal winter releases are 17,000 cfs.

As of Monday, the amount of water stored in the Missouri River's six reservoirs was at 61.9 MAF, occupying 5.8 MAF of the 16.3 MAF of the system's flood storage capacity.

In response to a question from the audience, Remus said the corps has been unable to increase releases from the reservoirs to higher levels this fall because of the continued above-average precipitation across the region that filled rivers such as the Vermillion, James and Big Sioux in South Dakota, the Little Sioux in Iowa and the Platte in Nebraska. Those rivers all feed into the Missouri beneath the reservoirs and have kept river levels high in Omaha and points south, limiting the progress on levee repairs in southwest Iowa, southeast Nebraska and Missouri.

"We're doing everything we can to manage the flood and move on to recovery from flooding," said Col. Torrey DiCiro, deputy commander of the Corps of Engineers Northwestern Division.