The short answer is no.
The mean outflow during the month of July was 1,227 cfs from 1970-2000 and 1,173 cfs from 2001-2023. Mean outflow during August was 1,173 cfs in the 1970-2000 period and 920 cfs in the 2001-2023 period.
Outflow may seem higher for two reasons:
1) Aquatic plant abundance is much higher now than it was decades ago, which makes the water deeper at a given outflow.
2) Turbidity is higher now than it was decades ago, so the water appears deeper than it really is because it’s harder to see the bottom of the river.
The reasons for higher macrophyte growth and higher turbidity are somewhat complex but can be roughly boiled down to changing climate and increased nutrient concentrations, the latter most likely tied to development.
1) Irrigation diversion is around 20% lower than it was in the 1970s-1990s as a result of increased irrigation efficiency, primarily conversion from flood irrigation to sprinkler irrigation. HFF recently published a groundbreaking paper on this subject.
2) Water management has become much more precise over the past 10 years due to remote-controlled irrigation technology and a lot more stream and canal gaging. In the Henry’s Fork watershed, we led the technological advances and funding acquisition that made this possible.
Since the start of Precision Management efforts in 2018, the amount of water left in Island Park Reservoir at the end of the irrigation season has exceeded expectations based on water supply by 26,000 ac-ft/year (over 10,000 Olympic swimming pools worth of water). This has been accompanied by a 100-cfs decrease in summertime outflow, despite the fact that water supply is 15% lower than it was in the 1970s-1990s. If we had the same water supply we had in the 70s-90s, it’s fathomable that we would hardly use any reservoir storage at all these days.
As it is the afternoon of December 31, I am closing the year with my annual fish-of-the-month blog, this one at the end of my 11th year of catching a fish in my home waters in each month of the year. To spare you the math, that’s 132 consecutive months of catching a wild trout or whitefish (and in some years I’ve fair-caught suckers and shiners, too) within a three-hour drive of my home in
In this blog post, we 1) present our turbidity and suspended sediment data, 2) explain our suspended load calculations, and 3) provide some additional information justifying why we think that a substantial amount of bed load was transported into the Henry’s Fork in addition to the suspended load. Since first observing high turbidity in Thurmon Creek and the Henry’s Fork downstream associated with the Silver Lake drawdown in November 2025, HFF’s Science and Technology team
Written by Doris Squeri Tom and I met on our first day of grad school back in 1982. We were both broke and stressed, and we both loved the outdoors, so I decided that an affordable way to relieve some of that stress might be to learn how to fly-fish. We had learned to fish with our dads when we were very small, but it was bait fishing, and we wanted to try something new.
The Henry’s Fork Drought Management Planning Committee (DMPC) met on Monday, November 24 to set this winter’s outflow and reservoir-fill strategy for Island Park Reservoir—an annual decision with implications for winter trout habitat in Box Canyon and the Ranch. Winter Outflow: What’s Coming on December 1 Beginning December 1, outflow from Island Park Dam will increase, bringing winter streamflow through Box Canyon to ~380 cfs from December through February*. That equates to 76% of Box
