Our macroinvertebrate studies support clear evidence that the insect hatches on the Upper Missouri River have changed and dramatically diminished over the last few years. Both the caddis fly and mayfly populations have been significantly impacted. We have determined the most likely cause for this phenomenon is a lack of high-water flushing flows in the spring/summer. This has allowed excessive weed growth and increased siltation of the riverbed gravel necessary for the successful reproduction of these insects.
In response to the problem, UMOWA has organized meetings with the Bureau of Reclamation which controls outflows from the Canyon Ferry reservoir as well as Northwestern Energy, which operates both Holter and Hauser dams. Our hope is that our negotiations will result in planned, periodic flushing flows of the river.