With Montana's spring runoff into the Missouri River not materializing, the U.S. Army Corps of Engineers is predicting this could be the 22nd driest year in the upper basin since 1898.
Drought conditions are expected to continue throughout June in much of Montana, according to the agency's forecast.
The Corps released its updated 2021 upper basin runoff forecast this week, which is estimated as 17.9 million acre-feet (MAF), 69% of average. The May upper basin runoff was 64% of average.
May runoff in the Fort Peck and Garrison reaches, where much of the upper Missouri's runoff from mountain snowmelt originates, was 60% and 68% of average, respectively.
“Per our June 1 upper basin forecast, we expect runoff to continue to be well-below average through the summer and fall,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.
Fort Peck Reservoir's elevation is 2,233 feet. Last year at this time it was 5 feet higher and in 2019 was up 11 feet compared to this year.
With the lower water forecast, the Corps will reduce flows in the lower river, where barge traffic occurs, by 1,000 cubic feet per second for the second half of the navigation season.