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Bighorn River 2018 Runoff Forecast

The Shoshone, Wind, and Bighorn Basins located in Wyoming, feed the Bighorn River here in Montana. This map shows near current snow water equivalents as a percentage of normal.

We have plenty of snow piling up in the Bighorn Valley, and more importantly, in the mountain ranges that feed the river!

Water is generally a good thing for rivers and trout. But the last few seasons, we have, at times, had too much of a good thing. This was especially obvious last spring when flows peaked at 15,000 cubic feet per second (cfs). The Bighorn River Alliance has been aggressively lobbying the US Bureau of Reclamation, which operates Yellowtail Dam here on the Bighorn, to be more proactive in dealing with water runoff in years when it is clear that there is going to be an excess. This year is shaping up to be a year of excess, with snowpack levels well above average in the Wind, Bighorn, and Shoshone Basins which feed the Bighorn River in Montana.

This week the Bureau of Reclamation (BOR), which operates the dam, released their spring runoff projections. The good news is that it appears the BOR is listening and planning accordingly in order to avoid extremely high flows this season. Current water releases out of Yellowtail Dam are at 4,500 cubic feet per second (cfs), which is higher than normal for this time of year. But this is a good thing, because it is making room in the reservoir for spring runoff that will come later. According to BOR, Bighorn River flows are expected to peak at about 7,000 cfs in May before dropping to 4,500 cfs in July.

This is great news! The river should have a ‘bump’ in spring flows. Increased flows in the spring helps cleanse the river of silt and algae which is good for insects and the trout that feed on them. Higher spring flows also facilitate better spring spawning conditions for rainbow trout. So having the river flow at 7000 cfs for a couple of months isn’t really a bad thing, and is extremely manageable from a fishing and guiding standpoint.

Generally speaking, the river tends to fish very good at these levels. We expect the spring nymph fishing will be very good. At the same time, we should still see good blue wing olive (baetis) and midge hatches in April and May. The predicted water levels will still be wadeable in spots, making it possible to take advantage of dry fly fishing opportunities.

Obviously we are keeping our fingers crossed that the Bureau of Reclamation’s projections will hold true, because if they do, it should set up some really good fishing conditions this spring!

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