Fishing Reports

Henry’s Fork, March 16th, 2024

Limited access prevails along the lower river. BWOs are out and with an extra hour of daylight more time is available to enjoy trout responding to them. Expect the river to cloud a bit as the warm weather will enhance bank side and nearby melting.

• Water-year total precipitation stayed at 106% of average, while SWE dropped a percentage point to 95% of average.
• Dry and warm weather is expected for the next six days.
• At an outflow of 416 cfs, Island Park Reservoir dropped by 92 ac-ft yesterday and is 91% full, compared with 80% full on average.
• The upper Snake River reservoir system is 88% full, compared with 68% full on average.
• Total reservoir storage plus existing snowpack across the basin is high enough that water will be spilled out of the system at Milner Dam starting on March 25.

Details

New snow water equivalent (SWE) over the past four days ranged from 0.2 inch at Pine Creek Pass to 1.7 inch at White Elephant. Current SWE is 95 of average: 92% in upper Henry’s Fork, 97% in Fall River, and 99% in Teton River. Current SWE ranks 17th out of the 36 years (54th percentile), just ahead of 1998 and just behind 2002. After the upcoming six days of dry weather in the forecast, SWE will fall to around 91% of average and drop several places in the rankings.

Dry conditions with above-average temperatures are expected for the next six days, before precipitation returns late next week. Valley snowmelt is expected, and that will increase streamflow a little. However, below-freezing nights will keep mid- and high-elevation snowpack intact before more mountain snow and valley rain is expected late next week. Long-term outlooks are leaning toward above-average precipitation, with gradually cooling temperatures 1–2 weeks out.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

Henry’s Fork, March 9th, 2024

Rainbow spawning has begun at least on the lower river with most activity occurring under low light conditions. Thus it is vital not to disturb even unoccupied redds.because of the presence of fertilized eggs.

Headlines from Dr. Rob Van Kirk’s Henry’s Fork Drainage SWE Status Report Filed Yesterday3/9

• More precipitation from the Monday–Wednesday event trickled into gages yesterday, keeping the water-year total at 106% of average. SWE dropped to 95% of average.
• Modest precipitation is expected again next Monday–Wednesday.
• At an outflow of 373 cfs, Island Park Reservoir gained 45 ac-ft yesterday and is 91% full, compared with 79% full on average.
• The upper Snake River reservoir system is filling rapidly at 86% full, compared with 76% full on average.
• Today’s precipitation-type take-home: Increasing spring and summer air temperatures have a doubly negative affect on water quality, directly via water temperatures and indirectly via lower water supply.

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Most of the SnoTel stations lost a little snow water equivalent (SWE) yesterday to sublimation, which is typical on cold days following a large snow event. That put net storm-total SWE increase at 1.4 inches, ranging from 0.2 inch at Crab Creek to 2.5 inches at Black Bear. Current SWE is 95% of average: 100% in the Teton headwaters, 97% in Fall River, and 89% in the upper Henry’s Fork. The watershed average currently ranks in the 54th percentile across the last 36 water years.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

Henry’s Fork, March 2nd, 2024

Yes, the current storms have limited access to much of the river and its drainage. But consider that this unusual amount of snowfall means better potential for great fly fishing next season.

Headlines  From Dr. Rob Van Kirk’s Henry’s Fork Drainage SWE Report Filed March 2nd

• Moderate and more widespread precipitation yesterday ended a very wet month of February, increasing water-year total precipitation to 96% of average and SWE to 82% of average.
• Heavy precipitation is expected to continue for the next week, with the March monthly outlook leaning toward above-average precipitation.
• Mean outflow from Island Park Reservoir over the critical December–February period for trout survival was 411 cfs, 116% of average.
• Island Park Reservoir gained 4,732 ac-ft over the Dec–Feb period and is 90% full, compared with 78% full on average. Outflow will be reduced to 375 cfs next week to fill the reservoir a little faster.
• The upper Snake River reservoir system is filling rapidly and is 83% full, compared with 66% full on average.

Details

As important as the warm temperatures may end up being later this spring for reservoir ice-off and subsequent water quality, the bigger story of February 2024 was precipitation. The watershed mean for the month was 5.18 inches, 142% of average. February precipitation totals were 127% of average in Fall River headwaters, 130% of average in Teton headwaters, 143% of average in upper Henry’s Fork, and a whopping 218% of average in the valleys. That moved water-year precipitation from 84% of average at the beginning of the month to 96% of average this morning, ranking 18th out of the last 36 years.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL