Henry’s Fork, February, 19th, 2022
Dr. Rob Van Kirk’s water report of February 18th for the the Henry’s Fork drainage is below.
Headlines:
- Water-year total precipitation stayed at 90% of average yesterday, while SWE dropped to 75% of average.
- Island Park is 83% full, compared with 77% full on average, and the upper Snake River Reservoir system is 45% full, compared with 64% full on average.
- The new seasonal outlook issued yesterday calls for drought to persist through the spring.
Details:
Mean temperature yesterday was 3 degrees F below average. Light precipitation was recorded at scattered locations, averaging 0.04 inch over the watershed. The water-year total stayed at 90% of average, but snow water equivalent (SWE) dropped to 75% of average. Current SWE is fifth lowest for the date in the 1989-2021 record, ahead of 1991, 1994, 2001, and 2010. April-1 SWE in those other four years ranged from 59% of average in 2001 to 85% of average in 1991.
All signs point to a similar outcome this year. After light to moderate snow on Sunday and Monday, very cold but dry conditions are expected next week and into the first week of March. The new seasonal outlook for March-May issued yesterday calls for drought conditions to persist. Our best-case scenario this year is a snowpack about like last year’s, in the 80-85% of average range. However, when combined with near record-low stream base flows this winter, water supply will definitely be lower than it was last year.
Reservoirs continue to fill slowly but steadily. Island Park Reservoir is 83% full, compared with 77% full on average. Henry’s Lake is 90% full and very close to average. The upper Snake River reservoir system is 45% full, compared with 64% full on average. Even with above-average precipitation over the remainder of the winter, snowpack will not be sufficient to fill the upper Snake system.
Rob Van Kirk, Ph.D.
Senior Scientist
P.O. Box 550
Ashton, ID 83420
208-652-3567 OFFICE
208-881-3407 CELL
208-652-3568 FAX