Missouri runoff reduced again

Drought conditions evident

The U.S. Army Corps of Engineers has once again revised downward the amount of water expected to enter the Missouri River Basin this year. On the heels of what the Corps describes as “well-below average” runoff in March, the expected amount of runoff has been lowered to 21.3 million acre feet of water. That compares to March 1 expectation of 21.7 maf and the long-term average of 25.8 maf.

“March precipitation was less than 50% of normal over much of the upper Basin,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division in Omaha, Nebraska.

There is no customary runoff from plains snowpack to contribute to the Missouri Basin flows in what has become a very dry region where the fire danger vividly illustrates the lack of moisture.

Mountain snowpack, primarily from western Montana, was tracking at 83% of normal on April 4 with the average peak accumulation is just days away on April 15. The current 2021 runoff forecast for the Missouri River Basin for Lake Sakakawea is for 81% of average inflow.

Monthly runoff projections, based on current conditions and historic data, have been in decline for several months. Without additional moisture in the form of rainfall or heavy snowfall over the drainage, it appears future runoff outlooks will continue to decline.

The latest 3-week elevation forecast for Lake Sakakawea, ending April 23, has a projection of 1,836.1 feet, slightly more than a foot below the March 1 outlook. Outflow is expected to remain at 21,500 cubic feet per second through late April with inflow below 17,000 cfs.

A year ago Lake Sakakawea peaked at more than 1,845 feet. The March 1 outlook called for a 2021 peak of just under 1,843 feet, a number that will likely be lowered in the April projections which were not completely available at the time of this writing.


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