The upper Missouri River basin is likely to continue having runoff levels higher than usual but considerably lower than those seen last year, experts from the U.S. Army Corps of Engineers' Missouri River Basin Water Management Division said in a Thursday afternoon teleconference.
MRBWM Division Chief John Remus said during the call that about a month into the runoff season, the current estimate on the upper basin's total runoff for the year is 35.5 million acre feet, down 1.4 million acre feet from March forecasts.
Mike Swenson, the division's power production team lead, said there are currently 5.3 million acre feet less in system storage than there were at the same point last year.
"Currently, the system storage is at 58.7 million acre feet," Swenson said. "Utilizing 2.6 million acre feet of the total 16.3 of flood storage space, approximately 84 percent of the flood storage is available to store runoff in the coming months."
Kevin Grode, reservoir regulation team lead, said warmer than normal March temperatures in eastern and central North and South Dakota resulted in nearly twice the average upper basin runoff for the month. Runoff is currently forecast to be higher than average in every month of 2020, which Grode said is primarily due to wet soil conditions throughout the upper basin.
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Grode said 2019's 60.9 million acre feet was the second-highest upper basin runoff in the 122 years it's been recorded. By comparison, if 2020 estimates are correct, 35.5 million acre feet would be the 12th-highest runoff year.
National Weather Service Hydrologist Kevin Low said major flooding was observed in March in the James and Vermillion rivers in South Dakota, despite the year to date being generally dryer and warmer than usual.
That's in part because snow pack in east and central areas in the Dakotas was particularly heavy over the winter, Swenson said, with some areas getting between 4 and 6 inches of snow water equivalent. The snow pack in the Plains peaked on Feb. 20.
"Soil conditions still remain abnormally wet across much of the basin, so there does still remain an enhanced risk for flooding, especially across the eastern third of the basin," Low said.
Whether flooding continues throughout the year, Remus said, will be dependent in part on the expected runoff's timing.
"The corps is well aware of the damage that last year's flooding has caused, and we are doing all we can to reduce the impacts and assist in the recovery," Remus said.
