It is time for terrestrial insect patterns almost anywhere you fish the river. As well as hopper patterns, include ant patterns, honey, red, and black in that fly box especially if you try the river in Island Park..
Here are excepts from Rob Van Kirk’s latest (today) analysis of the Henry’s Fork drainage water status.
Headlines:
- Yesterday was dry but pleasantly cool.
- Natural flow stayed at 75% of average yesterday but is dropping slowly in Fall River and Teton River.
- Diversion continues to increase very slowly, including a couple of incremental increases in Crosscut Canal delivery since yesterday afternoon.
- At an outflow of 740 cfs, Island Park Reservoir dropped by 594 ac-ft yesterday and is 46% full, compared with 62% on average and 28% in 2016.
Details:
Mean temperature yesterday was 4 degrees F below average, and no precipitation was recorded. The water-year total stands at 78% of average. Dry weather is expected to continue for the rest of the week, but forecasts continue to include a small chance of precipitation for next week.
Natural streamflow is decreasing very slowly on Fall River and Teton River but staying relatively constant in the upper Henry’s Fork, at least relative to a few flow drops at Ashton Dam over the past few days that confound the calculations. Natural flow was 75% of average again yesterday, about where it has been for the past few days. Natural flow is still a little higher than it was prior to the recent wetter weather that began two weeks ago today.
Diversion continues to increase very slowly, primarily on the Teton River. As a result, delivery through the Crosscut Canal was increased by around 15 cfs yesterday evening and another 10 cfs this morning. The supply-demand graph shows that my “600-cfs rule” continues to perform well. Natural flow minus diversion increased to around +600 cfs late last week (natural flow was 600 cfs greater than diversion), indicating little or no need for draft of Island Park Reservoir. Indeed, the reservoir actually stayed constant for a few days during that time. As we move farther away from last week’s wet weather, natural flow will continue to decrease, and diversion will continue to increase. However, stream flow in the lower Henry’s Fork remains well above the irrigation-season target today, which will absorb the increasing difference between natural flow and diversion without immediate need for additional outflow increases at Island Park Reservoir.
At an outflow of 740 cfs, Island Park Reservoir dropped by 594 ac-ft yesterday and is 46% full, compared with 62% full on average and 28% full in 2016. Together, the three reservoirs in the watershed are 65% full, compared with 74% on average and 55% full in 2016.
Outflow from the reservoir is being split between the dam gates and the power plant, resulting in lower turbidity than we saw last week, when all outflow was passing through the gates.
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
