Henry’s Fork

Henry’s Fork, November 28th, 2023

Headlines from Dr. Rob Van Kirk’s Henry’s Fork Drainage Water Status Report Filed Yesterday

• The Thanksgiving storm stayed to our south, leaving us with only 0.12 inch of precipitation.
• Water-year total precipitation is 99% of average this morning, the first time it has been below average this water year.
• Natural flow has dropped very slowly over the past week and was 92% of average yesterday.
• At an average outflow of 228 cfs, Island Park Reservoir has gained 364 ac-ft/day over the past week and is 85% full, compared to 63% full on average.
• Current reservoir volume is equal to the April-10 average.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

[email protected]

• Access remains good on the river below Ashton Dam, however water temps are dropping to a level that impact fish activity. Brown trout are still in a spawning mode, so streamer patterns of choice are still effective, with middle of the day being best time to fish. Same applies to sporadic midge hatches. Presenting nymph patterns of choice can be effective.

Henry’s Fork, November 21st, 2023

Headlines from Dr. Rob Van Kirk’s Henry’s Fork Drainage Water Status Report filed Yesterday,11/20

• Light precipitation fell over the weekend as expected; the water-year total is 117% of average.
• Another round of very light precipitation is expected on Thanksgiving Day, and long-term forecasts call for continued dry conditions.
• After flattening out for a few days, natural flow increased a little yesterday in response to precipitation.
• At an average outflow of 230 cfs, Island Park Reservoir gained 472 ac-ft/day over the past three days and is 84% full, compared to 61% full on average.

BWO activity is quickly diminishing on the entire river. It will return to significance sometime next March depending on weather and water conditions, Midge activity remains throughout the year, and under the right conditions can be almost massive at times. So we are entering the time when nymph and streamer patterns are most effective on the entire river.

Henry’s Lake, November 18th, 2023

Bets are that Henry’s Lake will ice over this coming week with colder and unsettled weather coming! So we had a longer season this year for wading and boating than last year.

Henry’s Fork, November 13th, 2023

Fun Farm Bridge at Dusk

This great weather will not last much longer, so get out and enjoy. Daytime hours are not only pleasant, but hold the best BWO and midge activity making their life cycle patterns a must for the fly box. Next week looks like normal November conditions will prevail.

One of the best happenings on the river is that aquatic vegetation has broken away giving more “fishable” water and a better chance for landing that big fish ( no weeds to bury into). Fly rod jigs are a good bet for streamer action with fish now concentrated in deeper water up and down the river. Plunk one into the top of any deep waters, let it sink and drift a bit, then retrieve with a “jigging motion” to make it rise and fall in the water column.

Headlines From Dr. Rob Van Kirk’s Henry’s Fork Drainage Water Status Report Filed Yesterday.

• Last week was warm and dry, dropping water-year precipitation to 134% of average.
• Generally dry conditions are expected to continue this week.
• Natural flow continues to drop from its November 3 peak, but rate of recession has dropped to around 2% per day.
• At an average outflow of 226 cfs yesterday, Island Park Reservoir gained 448 ac-ft and is 81% full, compared to 58% full on average.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

208-652-3568 FAX

[email protected]

Henry’s Fork, November 11th, 2023

What applies to the South Fork with respect to fishing strategy much applies to the river below Ashton Dam. For the upper river streamers and double nymph rigs work best in such as Box Canyon and the Tubs. Flow is down ( about 200 cfs) in Box Canyon to the point that hard sided boats have a tough time avoiding its emerging structure. Day time is best for top water fishing and is comfortable as long as nice weather prevails. Remember that the fishing season in Harriman State Park closes on November 30th.

Henry’s Fork, November 7th, 2023

Headlines from Dr. Rob Van Kirk’s Henry’s Fork Drainage Water Status Report Filed Yesterday

• Last week was warm and very wet, leaving water-year total precipitation at 159% of average this morning.
• Despite loss of snow at elevations below 7,000 feet over the weekend, SWE is 115% of average.
• Natural flow increased to 110% of average over the weekend in response to rain and sno wmelt.
• At an average outflow of 205, Island Park Reservoir gained 623 ac-ft/day over

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

208-652-3568 FAX

[email protected]

It is great weather and sky conditions for BWO activity and fish responding during mid-day hours. These conditions also have a good impact on streamer fishing anywhere on the river.

Henry’s Fork, October 31st, 2023

Headlines from Dr..Rob Van Kirk’s Henry’s Fork Drainage Water Status Report Filed October 30th, 2023

• Last week was cold and wet, moving water-year total precipitation up to 153% of average and commencing mountain snow pack accumulation.
• Although temperatures are expected to climb back above average, an extended period of very wet weather is expected to begin later this week.
• Natural flow has dropped from its rain-driven peak on Friday and is 98% of average.
• At an average outflow of 205 cfs, Island Park Reservoir gained 435 ac-ft/day over the weekend and is 76% full, compared to 54% full on average.

Rob Van Kirk, PhD.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CELL

Except for midge and BWO activity, say goodbye to reasons for top water fly fishing, but use their life cycle patterns. Concentrate on offering nymph and streamer patterns anywhere on the river for the next several months. Daytime fishing will improve with minimal ice in the guides compared to during frosty early AMs and evenings. As snow accumulates, expect diminishing access throughout the river. Happy Halloween!

Henry’s Fork, October 24th, 2023

Headlines From Christina Morisett’s ( subbing for Rob Van Kirk who is taking time off to fish) Henry’s Fork drainage report filed yesterday

• Last week was warm and dry.
• Cold, wet weather is expected for the next week—including the possibility for snow.
• Natural flow and diversion are 92% and 90% of average, respectively.
• At an average outflow of 209 cfs, Island Park Reservoir gained 200 acre-ft/day over the weekend and is 72% full, compared to 52% full on average.
• —
• Christina Morrisett, PhD
• Water Resources Consultant · Henry’s Fork Foundation
• https://www.linkedin.com/in/christina-morrisett/

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

Fun Farm Bridge at Dusk

With minimal wind, BWO and mahogany dun activity should be enhanced during unsettled weather coming the rest of the week. .Presenting streamer patterns of choice to migrating browns along the lower river and into good holding water anywhere in the upper river should be effective. But watch the weather because the first snows of the season mean many drivers have trouble adapting to slippery roads. Dress warmly, and be sure to fix any holes in those waders because water temps in the 40s, Deg. F leaking in can quickly dampen any trip to he waters!

Henry’s Fork, October 21st, 2023

Brown trout fishing success is happening on the lower river, and upcoming unsettled weather should enhance this happy situation. However, top water action continues because of BWO and mahogany dun, midge and caddis activity and fish feeding on these. Evenings are a good time to enjoy fish responding to this activity. Early sunsets make it convenient to head home or to a favored restaurant or ‘wateringhole” to enjoy a hearty dinner while savoring the day’s fishing success.

Henry’s Fork, October 17th, 2023

Wait for the wind to die down if you are fishing top waters anywhere on the river for BWO, caddis, midge, and mahogany activities. Wind is one of the worst enemies of aquatic insects that go to the surface to mature and lay eggs. Simply said; with windy conditions, they blow away before completing their purpose. If winds dies down during evenings, that is the time of day to see an increased density of these insects being active, and salmonids will respond this time of day.

Headlines 10/9

Headlines from Dr. Rob Van Kirk’s Henry’s Fork Drainage Water Status Report filed Yesterday, 10/16/2023

• The new water year started out near average in temperature and wet, continuing the pattern that started in early August.
• More precipitation is expected tomorrow through Thursday.
• At an average outflow of 341 cfs, Island Park Reservoir has gained 284 ac-ft/day over the past six days and is 67% full, compared with 48% on average.
• The upper Snake River reservoir system is filling slowly and is 43% full, compared with 39% full on average.