Henry’s Fork, May 9th, 2023

Headlines from Dr. Rob Van Kirk’s SWE Report Filed Yesterday for the Henry’s Fork Drainage

• Temperatures and snow melt were lower yesterday than earlier in the week but still above average.
• Natural stream flow increased yesterday to average but is likely to level off today, depending on location and amount of rainfall.
• At an average outflow of 695 cfs, Island Park Reservoir gained 421 ac-ft yesterday and is 86% full, compared with 93% full on average.

Water quality

Turbidity continues to increase across the watershed in response to snow melt and increasing stream flow. Turbidity is particularly high right now in Fall River and other tributaries such as Robinson Creek. Water temperatures dropped back to average yesterday at all locations except Island Park Dam, where ice cover has kept temperature at 39 degrees F. Our water quality data show no signs of open water on the reservoir yet. Ice melted last year on May 6, the latest date of ice-off we have observed since installing our water quality instruments in 2014. This year’s ice-off date is likely to be 4-6 days later than that

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Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL