Henry’s Fork

Henry’s Fork, August 13th, 2022

Some of the best fishing on the upper river is in Box Canyon where golden stone flies and terrestrial insects are providing good activity. Visit the river here during daytime hours, and expect recreational boaters to be present especially during weekends. With respect to recreational boaters expect the same on the lower river where terrestrial insects provide some early and late in the day decent fishing success.

Henry’s Fork, August 9th, 2022

Think terrestrial insect patterns just about anywhere you try the Henry’s Fork. Ants, In particular honey ants will be coming on strong with respect to interesting trout. Dry-dropper rigs also produce in such as Box Canyon, Cardiac Canyon, the Flat Ranch, and Warm River to Ashton.

Headlines from Dr. Rob Van Kirk Henry’s Fork drainage water status report of yesterday follow.

Headlines:  

• Temperatures climbed above average yesterday, and no precipitation was recorded. Potentially heavy precipitation is expected again late this week and into the weekend.
• Watershed-wide natural flow decreased yesterday to 75% of average, while diversion increased a hair.
• At an outflow of 777 cfs yesterday, Island Park Reservoir dropped by around 500 ac-ft and is 62% full, which is average for the date.
• Water quality: Turbidity at Island Park Dam reached its highest values since last fall yesterday but has dropped quite a bit over the past 18 hours.

Dr. Rob Van Kirk PhD

Senior Scientist

Henry’s Fork Foundation

PO Box 550

Ashton, ID 83420

208-881-3407 CELL

Henry’s Fork, August 6th, 2022

Throughout the river Early AMs and evenings offer the best fishing as well as the lowest number of recreational floaters. These folks are most numerous during weekends with Box Canyon, Warm River to Ashton, Ashton to Chester and the river below St. Anthony being where they are most concentrated.

For now, consider minimizing visits to the the river from Ashton Dam to Chester to give trout a break from tough recoveries through being played in warm water..

Warm River to Ashton offers good fishing especially for those concentrating presentations toward banks. We suggest hopper patterns and such as chubby chernobyls on top to drift suspended nymph patterns of choice in the water column below.

Headlines from Dr. Rob Van Kirk’s Henry’s Fork drainage water report compiled yesterday are below.

Headlines:  

• Yesterday’s mean temperature was 3 degrees F below average, and a few showers were recorded in the Teton sub-watershed.
• Natural flow in Fall River and Teton River continues to benefit from the effect of Tuesday’s rain, while diversion dropped by another 7% yesterday.
• Outflow from Island Park Reservoir was reduced to 900 cfs yesterday, and additional reductions are likely over the next week.
• Fishing conditions: Streamflow across the watershed is well below average for the date, turbidity is average in all stream reaches, and water temperatures have likely peaked for the year.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-881-3407 CEL

208-652-3568 FAX

Henry’s Fork August 2nd, 2022

Throughout the river early AMs and evenings remain the best fishing. Thinking of trying the river during weekends? Be ready to share it with recreational floaters.

Headlines from Dr. Rob Van Kirk’s Henry’s Fork drainage report compiled yesterday are below.

 Headlines:

• The daily maximum temperature yesterday was the warmest since July 26 of last year, but cooler temperatures are expected over the next week.
• Diversion and natural flow both dropped a little yesterday, increasing stream flow in lower Fall River and lower Henry’s Fork.
• At 240 cfs, current Crosscut Canal delivery to the Teton River is meeting irrigation demand and stream flow targets there after exchange well pumping was reduced a few days ago.
• Island Park Reservoir is 65% full, compared with 67% full. Outflow reductions are possible this week, depending on stream flow and diversion response to rain and reduction in outflow from Grassy Lake.
• Flow out of Grassy Lake Reservoir will be reduced resulting in a 100 cfs flow reduction in Fall River.

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

Henry’s Fork, July 26th, 2022

Other than spinner falls and caddis activity, we are in the time of the season where terrestrial insects are taking over as a major food form for trout.anywhere you fish the river. Be sure you have patterns for such in that fly box. And as time passes through summer, ant patterns will become of increasing effective among these.

Here are headlines from Dr. Rob Van Kirk’s Henry’s Fork drainage water report filed yesterday AM.

Headlines:  

• Warm, dry weather will continue for the rest of the week.
• Natural flow stayed constant at 63% of average yesterday, while diversion continued to drop and is 88% of average.
• Outflow from Island Park Reservoir was reduced by 100 cfs yesterday, and additional reductions are likely over the next week.

Henry’s Fork, July 23rd, 2022

Box Canyon, Warm River to Ashton, and Ashton Dam to Chester backwater sections are seeing a big increase in recreational floaters. The peak of this activity is usually from late morning to late afternoon. For the latter two locations, this time stretch coincides with the slowest fishing success. Minimize your interaction with these folks by fishing early AMs and during evenings when fishing success is much likely best during these warm days. Everywhere on the river, bank side terrestrial insects are taking over as being a most important food form for foraging trout. Carry fly patterns that simulate them and concentrate your presentations to banks above good holding water.

Here are headlines from Dr. Rob Van Kirk’s Henry’s Fork drainage water report compiled yesterday, July 22nd.

Headlines:  

• Dry weather with temperatures 2-4 degrees F above average is expected to continue for the foreseeable future, as drought redevelops along the northern edge of the watershed.
• Current USGS gage readings are around 80 cfs higher at Island Park and 300 cfs higher at Ashton than actual stream flow.
• At an outflow of 1423 cfs yesterday, Island Park Reservoir is 77% full, right at average for the date.
• No large changes in irrigation-system management are expected for another week or so.

Here are

Henry’s Fork, July 19th, 2022

Terrestrial insect populations are building along banks throughout the length of the river as the variety of aquatic insects decreases. Begin thinking patterns for such as ants, beetles and hoppers anywhere you fish the river, and target holding water along vegetated banks. Some turbidity is present in waters released from Island Park Reservoir and this condition continues on downstream through the Harriman State Park section. Best fishing is during AM spinner falls and remaining mayfly activity during late afternoons. This” best fishing times comment” applies to the entire river. Upcoming speckled dun and trico activity will “revitalize” this.

If you fish the river below Ashton Dam, consider that the warmer the water, the tougher it is for fish to revive after being caught and released.

Headlines from Dr. Rob Van Kirk’s Henry’s Fork drainage water status report from yesterday follow.

Headlines:  

• Mean temperature yesterday was 3 degrees F above average, and water-year total precipitation at 90% of average.
• Natural flow has dropped a little to 80% of average over the past few days, while diversion increased a little yesterday to 98% of average.
• At an outflow of around 1450 cfs, Island Park Reservoir is dropping at around 1700 ac-ft per day and is 81% full.
• Current system management continues to keep stream flow in the lower watershed very stable, and no large changes are anticipated in the short term.

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

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Henry’s Fork, July 12th, 2022

Headlines from Dr. Rob Van Kirk’s latest water report for the Henry’s Fork follows.

Headlines:  

• Mean temperature yesterday was 2 degrees F above average; water-year precipitation stands at 90% of average.
• Natural flow dropped another 3% yesterday, while diversion increased to 99% of average. Water rights priorities are near the median for the date.
• Outflow from Island Park Reservoir was increased to 1460 cfs yesterday to accommodate increased diversion into the Crosscut Canal.
• Diversion and reservoir outflow will remain high for the next 2-3 weeks, as hot, dry weather continues.

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

Evenings ( try caddis and PMD and gray drake spinner patterns) and early AMs ( spinner patterns again) are the best times to fish the lower river where terrestrial insects are beginning to appear in good numbers. A bit early for these along the upper river except ant and beetle patterns should always be in that fly box Variable flow out of Island Park Reservoir impacts fishing from Box Canyon to Riverside. PMDs, Flavs and green drakes are diminishing a bit (AM and PM spinner falls bring action) except for PM brown drakes in lower Harriman offering best activity. PM caddis activity is reliable everywhere.

Henry’s Fork, July 9th, 2022

The river from Ashton Dam downstream is beginning to warm as our “dog days” are here. This means best fishing will be early AMs and evenings, Major aquatic insects are diminishing, but terrestrial insects will soon be plentiful. Wading and boat traffic on the Last Chance-Harriman section is high, but fishing is good as the usual aquatic insect hatches continue at good levels.

Plenty of water ( currently about 170 cfs) is flowing through the river at the Flat Ranch Preserve. This flow started late because of water managing efforts in this drought year. That means fewer fish were swept downstream out of Henry’s Lake than usual. Nevertheless, the river here is worth a try.

Henry’s Fork, July 5th, 2022

We have reports of recreational floating traffic on the river; Box Canyon and the entire lower river between above Chester seem to be favored locations. Consider that these folks do not understand angling etiquette. So be patient. They have just as much right to enjoy the river as do anglers. Best time to fish around them is early and late in the day.

All traditional hatches are in full swing along the river: Green drakes, flavs, PMDs, PM caddis abound with a few golden stones. Brown drakes are appearing in evenings on lower the river at Harriman East making Wood Road 16 an up and coming favored location. AM and PM spinner falls are good times to be on the river whether it be Last Chance-Harriman State Park waters or the lower river. These times of day minimize recreational traffic. Also dry-dropper combos seem to work everywhere. Try a dry blond humpy over a bead head nymph of your choice

Headlines from Dr. Rob Van Kirk’s latest Henry’s Fork drainage water conditions report follow:

Headlines:  

• The first 4 days of July were slightly on the warm side of average, and a few thundershowers kept water-year precipitation at 91% of average.
• Natural flow has dropped by 1-2% per day over the past four days, while diversion has stayed relatively constant.
• Since an outflow increase on Saturday, Island Park Reservoir outflow has averaged 991 cfs, and the reservoir has drafted at 930 ac-ft/day. Additional incremental increases in outflow are expected.
• Water quality: Water temperatures have been optimal except at St. Anthony, while turbidity is still above average at all locations upstream of Ashton Reservoir. 

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