For the last couple of decades ND residents near Lake Sakakaweja have been told the spring releases from the Garrison Dam were being done to float barge traffic down river to extend the commercial shipping season. Friends who retired on lakefront property saw the lake level decline to the point they were half a mile from the water, and the whole time the Corps was repeating the mantra about the economic necessity of barge traffic. Businesses folded, boat ramps were high and dry, lake access was limited and the local sport fishing and tourism industry suffered outrageously, but some barges at St. Louis were more important.
What is happening now is the result of record snowfall over the winter and continuing rain.
I'm not sure what was done in the Oahee Reservoir, but Ft. Peck and Sakakaweja have been kept low over the last few decades on the premise of facillitating navigation downstream.