Flushing Flows
Advocating for Change: Restoring Natural Flow Patterns
The Problem
UMOWA's macroinvertebrate research demonstrates that insect hatches on the Upper Missouri River have substantially diminished in recent years, with caddis fly and mayfly populations severely affected.
The root cause is the absence of high-water flushing flows during spring and summer months. This has enabled excessive aquatic vegetation growth and increased sediment accumulation on the riverbed gravel essential for insect reproduction.
Taking Action
UMOWA has initiated negotiations with the Bureau of Reclamation, which controls Canyon Ferry reservoir outflows, and Northwestern Energy, which operates Holter and Hauser dams. The objective is to establish planned, periodic flushing flows that mimic natural hydrological patterns and restore the ecological health of the river.
By restoring these natural flow patterns, we aim to reduce excessive aquatic vegetation, scour accumulated sediment from spawning gravels, and create the conditions necessary for healthy macroinvertebrate populations to recover.
Related Research
Explore the scientific studies that inform our advocacy for flushing flows.
Scientific investigations into the health of aquatic insect populations.
Learn MoreUnderstanding excessive aquatic plant growth in the Upper Missouri River.
Learn MoreMonitoring water chemistry and quality in the Upper Missouri River.
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