Fishing Reports

Henry’s Fork, November 23rd, 2021

Snow shoes or X-country skis will help if you intend to fish the river in Island Park! Nymph patterns, large and small, and streamer patterns will be best candidates for action here and in the lower river as well.

There is near global interest in how 2021-2022 winter snowfall/water conditions will impact next season’s fishing conditions in the Henry’s Fork drainage.

Through the upcoming winter we therefore will post the Henry’s Fork Foundation’s Dr. Rob Van Kirk’s weekly summary of these conditions. Information from Dr. Van Kirk’s summary prepared on November 22nd follows.

Headlines:  

• Yesterday was warm and dry, and with the exception of a little snow today and tomorrow, warm and dry conditions will continue for the next week.
• Natural flow dropped yesterday in response to a cold morning and is 78% of average.
• At a mean outflow of 119 cfs, Island Park Reservoir gained 481 ac-ft yesterday and is 66% full, compared with 61% full on average.

Details:

Despite a cold start to the day, mean temperature yesterday was 3 degrees F above average. No precipitation was recorded. Except for some light snow today and tomorrow, generally warm and dry conditions are forecast for the next week. Precipitation is tentatively forecast to return in the middle of next week.

Natural flow decreased a little yesterday as a result of cold overnight low temperatures. River icing was apparent in the Fall River hydrograph yesterday. Watershed-wide natural flow was 78% of average yesterday and within a few percentage points of that in each of the three subwatersheds. Cumulative natural flow for the water year so far is 77% of average.

At an average outflow of 119 cfs, Island Park Reservoir gained 481 ac-ft yesterday and is 66% full, compared with 61% full on average. At the current outflow, reservoir gain due to stream inflow has been in the range of 475-500 ac-ft/day. Direct precipitation on the reservoir surface has added an additional 1000 ac-ft since the start of the water year, equivalent to an additional 10 cfs of inflow, 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

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Henry’s Fork, November 9th, 2021

Streamers and nymph patterns are the ” Name of the Game” up and down the river now.

All of us are interested in what upcoming winter snowfall and water situations will be for the Henry’s Fork drainage. Such information can provide likely water conditions during the next angling season. Thus we will continue reporting what information Dr Rob Van Kirk assembles each week on the drainage water conditions. Information Rob offers from his Monday,November 8th report follows.

Headlines:  

• Yesterday’s mean temperature was the coldest since March 31, and some precipitation lingering from the weekend was recorded very early yesterday morning.
• Natural flow has dropped a little over the past day or two to 73% of average for the date.
• At a mean outflow of 120 cfs, Island Park Reservoir gained 473 ac-ft yesterday and is 60% full, compared with 57% full on average.
• Above-average temperatures and near- to above-average precipitation are expected to continue.

Details:

Yesterday’s mean temperature was the lowest since March 31, although it wasn’t even all that cold, at 3 degrees F below average. A little precipitation leftover from Sunday was recorded very early yesterday morning at a few locations in the northern and eastern areas of the watershed. Snow accumulation so far this fall remains below average, despite above-average precipitation. At least for now, the combination of warm temperatures and above-average precipitation is favorable to increase soil moisture prior to the inevitable arrival of widespread freezing temperatures and snow accumulation. In general, temperatures are expected to remain at or above average, and near- to above-average precipitation is also expected to continue.

Watershed-total natural flow has dropped a little over the past day or two and is 73% of average for the date and 75% of average for the water year so far.  

At an average outflow of 120 cfs, Island Park Reservoir gained only 473 ac-ft yesterday on a day without precipitation. Over the weekend, a substantial fraction of reservoir fill was due to direct precipitation on the reservoir. Precipitation forecast over the next week will add around 250 ac-ft over and above that due to stream inflow. The reservoir is 60% full, compared with 57% full on average.

G

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