U.S. Army Corps of Engineers anticipates high runoff season for Missouri River
Potential to be top-10 event
It is much too early in the winter season to say with any certainty how much snow or rain will fall between now and the annual spring runoff into the Missouri River system, but the U.S. Army Corps of Engineers says they are preparing for a high runoff season.
In fact, says the Corps, the 2020 runoff season already has the potential to be a top-10 historical event in terms of volume of water. The Corps issued that statement Tuesday during a briefing of interested parties all along the Missouri River system. Much of the concern over a potentially high runoff season centers on the soil conditions.
“Given the very wet soil conditions and stream conditions, we expect March and April runoff to be two-times more than average,” said Kevin Grode, Corps of Engineers in Omaha, Nebraska.
The early line, according to the Corps, is that 2020 runoff could be the ninth-highest in 122 years of record keeping. That amount follows the second-highest runoff ever recorded that occurred in 2019. Each runoff season is different, however. To date it appears Lake Sakakawea in North Dakota will be spared the worst of the runoff.
“For May, June and July it look like slightly above average runoff for Garrison,” said Grode. “Lake Oahe through Sioux City is expected to be well above average runoff in the summer months.”
The Corps stresses that the winter snow accumulation season, primarily in the mountains of western Montana, has not yet reached the half-way point.
“It’s still early and much will change,” said Kevin Low, National Weather Service hydrologist. “Right now the mountain snowmelt looks near average but soil conditions are very saturated.”
Low noted that flooding along the James River has reached 300 consecutive days, breaking records for longevity. Given the soil moisture content and existing snowpack in the James River drainage there appears to be little relief in the coming months.
“Our first official Flood Outlook will be issued February 13,” said Low. “It will be a quantification of flood potential for this spring.”
John Remus, Missouri Basin Water Management Division chief, said ice on rivers limits the ability to evacuate water during the winter.
“All of our flood control storage may not get evacuated,” said Remus.
Remus noted that the Bismarck area experienced high water issues as the combination of warm weather and releases from Garrison Dam led to a break up of ice that formed ice jams. To help alleviate the situation the amount of water being released through the Garrison Dam power plant was reduced.
Fort Peck Reservoir in Montana, Lake Sakakawea in North Dakota and Lake Oahe in both South and North Dakota have designated flood control zones to capture spring runoff. Although the bottom of those zones might not be reached, as referenced by Remus, the difference is expected to be only a few inches.