Fishing Reports

Henry’s Fork, October 30th, 2021

On the lower river, Box Canyon, Cardiac Canyon holes and runs deep, and the Tubs, presenting streamer patterns is the name of the game. If you favor top water fishing, BWO life cycle patterns provide the best action.

More information from Dr, Rob Van Kirk on Henry’s Fork drainage water status follows.

Headlines:  

• Precipitation yesterday was moderate and widespread again yesterday, averaging 0.4 inches across the watershed.    
• Natural flow has increased by 330 cfs (17%) since Friday and is 89% of average.
• At a mean outflow of 124 cfs, Island Park Reservoir gained 781 ac-ft yesterday, 110 of which was due to direct precipitation on the reservoir surface. The reservoir is 55% full, compared with 53% full on average.

Details:

Moderate precipitation continued yesterday at all locations, averaging 0.4 inch across the watershed. Precipitation was uniformly distributed across the watershed, and even valley areas received 0.2-0.3 inch. This pushed the water-year total to date to 3.63 inches, compared with the long-term average of 2.75 inches for the whole month of October. Temperatures dropped yesterday to 2 degrees F below average, the coolest in 11 days. As a result, most of the SnoTel stations gained new snow water equivalent (SWE) yesterday. White Elephant, Black Bear, and Grand Targhee each have over 1 inch of SWE on the ground. Small chances of precipitation continue on and off over the next week, with temperatures staying near average.

Watershed-total natural flow has increased by 330 cfs (17%) since Friday, with most of that increase occurring Monday and yesterday. Although streamflow in headwater areas peaked yesterday, some of that is still making its way to the lower watershed this morning. Natural flow yesterday was 89% of average for the date, and cumulative natural flow for the water year to date has increased a percentage point to 75% of average. Diversion incidentally increased by around 30 cfs yesterday due to higher river stage and was 93% of average. Total diversion for the irrigation year to date—which ends on Sunday—is 92% of average.  

At an average outflow of 124 cfs, Island Park Reservoir gained 781 ac-ft yesterday. Around 110 ac-ft of that gain was due to direct precipitation on the reservoir surface. The reservoir is 55% full, compared with 53% full on average. Over the next day or two, fill rate will gradually drop back to around 550 ac-ft/day, where it was prior to the recent precipitation event.

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-652-3567 OFFICE

208-881-3407 CELL

208-652-3568 FAX

[email protected]

Henry’s Fork, October 26th, 2021

As is our usual practice, excerpts from Dr. Rob Van Kirk’s Monday AM analysis of the Henry’s Fork drainage water status are given below.

REPORT NOTE: USBR data sites are down for maintenance this morning, so diversion, streamflow and reservoir data are current only through Saturday. I’ve filled in missing data for USBR weather stations with data from the nearest non-USBR stations.

Headlines:  

• Precipitation during the much-anticipated atmospheric river event has so far been highly variable, ranging from a few hundredths in the valleys to over 1 inch in the Centennial Range.    
• Diversion and natural flow were around 75% of average until rain increased natural flow in Fall River on Saturday.
• At a mean outflow of 110 cfs, Island Park Reservoir gained 549 ac-ft/day for the week ending Saturday and is 54% full, compared with 52% on average.

Details:

Mean temperature last week was 3 degrees F above average. At 8 degrees F above average, Friday was the warmest day since October 6. Precipitation for the week-—most of which has fallen in the past two days—was highly variable across the watershed, ranging from a few hundredths in the valley locations to 1.3 inches at White Elephant. The Centennial Range and Yellowstone Plateau areas have received by far the highest totals thus far during the much-anticipated atmospheric river event that is bringing heavy precipitation to most areas of the West. Lewis Lake Divide, Black Bear, White Elephant and Crab Creek all received over 0.6 inch of water equivalent last week. Because of warm temperatures, new snow accumulation has been limited to the highest elevations, where Black Bear and Grand Targee have 1.7 inches and 2.5 inches, respectively, of snow water equivalent on the ground–around 80% of average for the date. Precipitation is expected to continue today and tomorrow, with somewhat cooler temperatures arriving this afternoon.

Watershed-total natural flow and diversion stayed around 75% of average until rain on Friday night and Saturday morning increased streamflow in Fall River by 40 cfs or so. Streamflow in the Teton River is also increasing a bit this morning.

We measured outflow from Island Park Reservoir at 114 cfs on Friday. For the week ending Saturday, mean outflow was 110 cfs, and the reservoir gained an average of 549 ac-ft/day. Projecting that gain through the end of yesterday, the reservoir is 54% full, compared with 52% full on average.   

Rob Van Kirk, Ph.D.

Senior Scientist

Henry’s Fork Foundation

P.O. Box 550

Ashton, ID 83420

208-652-3567 OFFICE

208-881-3407 CELL

208-652-3568 FAX

Henry’s Fork, October 23rd, 2021

With the stormy weekend and first of next week predicted, brown trout will be active on the lower river, so break out those streamer patterns. Other than that BWO activity will be plentiful anywhere on the river. For the river in Island Park, the best news is that Highway 20 repaving between the Sheep Falls Road and Riverside Campground is complete, so no more flaggers and long lines of vehicles to slow down traffic.