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How did Senior Scientist Rob Van Kirk’s predictive models hold up this year?

Here are just a few excerpts from Rob's spring predictions and how that compares to what happened this summer.

Prediction vs Actual

"Natural streamflow for April-September is predicted to be 60% of average, compared with 68% of average in 2021. There is a slightly better than 50% chance that April-September streamflow this year will be lower than it was in 2001, the lowest in the 1978-2021 record."

As of right now, this number is 67% of average, and it is the third lowest in the record, behind 2001 and 1992.

"Hatch timing, at least early in the season, is expected to be later than normal in all reaches of the Henry’s Fork."

Very cold temperatures this spring have delayed aquatic insect development and emergence by 3-7 days relative to average, and 6-10 days relative to 2021.

"So what does all this mean for hatches in the Ranch this year? As expected, hatches were not as good in 2021 as in 2020, and our invertebrate data reflect that...Without a spring freshet in 2021, it is likely that the numbers of sediment-intolerant species will be lower this year even than last year..."

Anglers have reported that hatches this year (2022) were not great.

"...outflow from Island Park Dam will be around 1,500 cfs for most of July..."

Outflow was between 1100 cfs and 1400 cfs July 7 - August 3.

"As for water clarity, the expected high magnitude and long duration of high flows out of Island Park Reservoir this summer will result in higher-than-average turbidity. Furthermore, even if turbidity stays near average, the water will appear less clear just because it will be deeper."

As anglers know, turbidity was higher than average this year. View that data at

To receive daily water updates, email to be added to his email list. Broader updates will continue to be shared on social media, monthly e-newsletters, quarterly newsletters, and current conditions posters at Island Park access sites.



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