Big Hole River flows at Wisdom have slipped below 40 cubic feet per second (cfs). Water temperature with these low flows is peaking at 75 deg F. This reach of the Big Hole River is core habitat for a small and dwindling population of our native fluvial Arctic grayling.
According to the Big Hole Watershed Committee’s “drought management plan,” the target flow for the Wisdom reach is 160 cfs for 15 May through 30 June. This level is the upper inflection point for the river’s wetted perimeter, and is the level needed for good recruitment of young-of-the-year grayling. The lower inflection point, which many biologists consider to be a minimum survival level, is 60 cfs. Fish – especially an endangered fish like the Big Hole river grayling – need water everyday, not just 20 days out of 30.
The year-to-date precipitation is well above average. The monthly June precipitation is well above average. Why isn’t there enough water in the upper Big Hole River?
After what looked to be a pretty good year for grayling spawning & recruitment, have we “screwed the pooch?” Are we once again poised to kill off an entire year class of this endangered fish?
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