Henry's Fork River
Lower

The information below reveals that run-off has begun only in the Teton River drainage and is reflected by around or slightly more than normal flows in the lower river down to the Teton River confluence. It also suggests that the next few days will offer the most comfortable times to enjoy trout responding to BWO, March brown, and midge activity.

Rob Van Kirk, Ph.D.

Details From Dr. Rob Van Kirks SWE Report Filed Yesterday, April 11th, 2024

Snow melt increased natural flow in the Teton River yesterday (120%) while flow in the Fall River 76% 0f normal and 78% of normal in the Henrys fork..These amounts will increase until Monday when cooler atmospheric temperatures will begin to take place for several days.

Senior Scientist

Henrys Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

Cloudy skies are great for increasing the density of BWO, March Brown, and midge activity. But the stronger the wind the bigger the negative impact on these activities. That wind is happening now on the lower river, making evenings and early AMs the best times to enjoy fish responding to these activities. Improved weather is predicted for later next week, but be aware we are entering the run-off season as warm weather begins to dominate. If you are fishing streamers, the only impact wind has is on casting precision!

Headlines 4/5 From Dr. Rob Van Kirks SWE Report Filed April 5th for the Henrys Fork Drainage

Details

Dry conditions are expected for 710 days starting early next week. That will initiate widespread melt of snow at all but the very highest elevations.

Natural stream flow has increased by over 15% since Sunday due to snow melt. Natural flow was 95% of average yesterday: 90% in upper Henrys Fork, 97% in Fall River, and 104% in Teton River. I expect natural flow to continue to increase through tonight before cooler temperatures slow melt and drop stream flow over the weekend.

Rob Van Kirk, Ph.D.

Senior Scientist

Henrys Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

Major run-off has yet to reach the river as flows throughout are about normal for this time of the year. Based on Dr. Van Kirks information below, a greater than normal run-off could result from the high accumulation of snow in drainage streams originating in the Teton and Big Hole ranges and the southwest corner of Yellowstone Park. Look for run-off to begin as we warm in April and trout will hunker closer the bottom to pick off the abundance of drifting food forms. Right now on the lower river, BWOs and March brown mayflies and midges provide good top water fishing with best success during overcast days with little ( Is that possible?) wind. Presenting streamer, woolly bugger, and rubber leg patterns is also effective especially under these atmospheric conditions. Smaller nymph patterns drifted into holding water will also bring responses from resident salmonids. All this will change with the arrival of serious run-off. We will keep track of its progress to help with planning your fishing strategy.

Headlines from Dr. Rob Van Kirks SWE Report for the Henrys Fork Drainage Filed March 29th

Details

Mean temperature yesterday was right at average, and precipitation averaged 0.58 inch across the watershed, the highest one-day total since March 2. Precipitation heavily favored the upper Henrys Fork sub-watershed and Yellowstone Plateau, where all five SnoTel stations in that area received at least 0.8 inch of water equivalent. White Elephant led all stations yesterday at 1.6 inches. Totals elsewhere in the watershed ranged from a few one-hundredths of an inch to 0.5 inch. This was enough to move the water-year total up two percentage points to 104% of average, ranking 12th out of the last 36 years (57th percentile).

New snow water equivalent (SWE) accumulations ranged from 0.2 inch at Grand Targhee and Pine Creek Pass to 1.7 inches at White Elephant. All stations in the Island Park/Yellowstone Plateau area received 0.9 inch or better. The days totals moved watershed-mean SWE up two percentage points to 95% of average, ranking 21st out of the last 36 years (43rd percentile). Current SWE is at its seasonal maximum at all nine stations. This ensures that annual peak SWE at Island Park will occur later than its statistical average, which is March 27. Average date of peak SWE at Pine Creek pass is March 30, and given current conditions and weather forecasts, this years peak SWE there will likely also occur later than average.