Henry’s Fork, February 17th, 2024
Headlines from Rob Van Kirk’s Henry’s Fork Drainage Snow-Water Equivalent (SWE) Report Filed Yesterday
- Heavy precipitation yesterday moved the needle substantially, as water-year total precipitation increased to 97% of average and SWE to 81% of average.
- Lighter precipitation will continue off and on for the next week.
- Natural flow increased to 102% of average yesterday due to very warm temperatures.
- At an average outflow of 465 cfs, Island Park Reservoir gained 111 ac-ft yesterday and is 91% full, compared with 77% full on average.
Details
In recent years, we have seen the month of February turn a below-average snowpack into an above-average snowpack. The most striking example was 2019, when SWE improved from 79% of average on January 31 to 121% of average on February 28. Could that happen this year? Probably not with respect to snowpack, although February may bring water-year total precipitation back up to average. Total precipitation for the first 15 days of February has exceeded the monthly mean already, so February will definitely be the first month of above-average precipitation since October and will likely rank in the top 10 for February precipitation. If we receive average precipitation for the rest of the month—which is very likely—the water-year total will stay at 97% of average. However, current outlooks give a decent chance of above-average precipitation late in the month, so we could end the month a percentage point or two higher with respect to average.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-881-3407 CELL
Why do we offer this information ?
Much of the SWE information Dr. Van Kirk collects then offers on the Henry’s Fork drainage impacts the water quantity and therefore angling quality of the upcoming season. And that quantity is determined mainly by the snow accumulation of the previous winter. The activity of the salmonid population and the availability of the aqueous forms on which they feed are impacted by the amount of water in which they live. The fly fisher benefits from this information with respect scheduling visits that will provide the best chance for a satisfying angling experience. The fly fishing retailer benefits through helping to decide when to offer items ( flies in particular) specific to the time of the season.