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Beaverhead River flushing flows and update

We have been receiving a lot of questions from anglers and river users about the current condition of the Beaverhead River. If you have been watching the gauges, you have probably noticed that the river is flowing well above average for this time of year. The opener on the Beaverhead, and other rivers across the state is May 19, and this is when the section of river from Clark Canyon Dam to Pipe Organ bridge will re-open to angling.

Graph showing flow from April 14 – present

The Beaverhead River has been flowing at or near 600 cfs since April 19th, which was initiated in coordination with the MT FWP and local agencies. The initial flush raised the river from its winter flows of 75 cfs to approx. 600 cfs. The purpose of this release was to move fine sediment that has accumulated over the past year down the river channel, where it will be deposited in the flood plain, and be less harmful to invertebrates that reside in the river. After the 2100 acre-ft of water that is reserved by the FWP in Clark Canyon Reservoir was depleted, the outflow from the dam has roughly matched the inflow to the dam. “Roughly matched” is the key word here, as a lot of us have noticed that the inflows to the reservoir have (on certain days) far exceeded the outflows. This is where the initial “flush” goes away, and management of outflows is handed over to the Army Corps of Engineers and the Bureau of Reclamation (who knew so many agencies regulated on small reservoir in MT!?). When the reservoir reached the regulatory flood pool this spring, the Army Corp of Engineers requires the BOR to empty the flood pool, while being careful to not exceed the flood target of 800 cfs in Dillon, confusing, I know. So, in easy terms, the BOR is trying to manage the outflows from the reservoir while monitoring local precipitation, inflow to the river from tributaries, and outflows due to irrigation demands. Once those become a little more predictable, the inflows and outflows should once again, match.

We expect the river to be in great condition this year, because of current flows in the river, and because the reservoir is 100% full! With some luck, the Beaverhead should have good water levels throughout the summer.  Within the past week we have seen caddis starting to come off around Dillon. Once the warm weather returns, we anticipate that the Mothers Day Caddis hatch will come in full force.


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