Throughout August-September, there tends to be a lot of rooted aquatic plant (macrophyte) growth. These plants grow rapidly as they photosynthesize due to warmer water temperatures. Dense mats of aquatic plants displace water, making it appear like the depth is greater.
Think of the river as a bathtub. With a bathtub, the water level seems to increase when you step inside, as your weight displaces the water. It is the same with the river. The plants displace river water, making the river appear to be more full than it really is.
On average, macrophytes will continue to grow through early-to mid-September, but this is dependent on the weather. Once growth has peaked in the fall, macrophytes begin to decay and deteriorate, causing bits and pieces of old plant growth to float down the river. This is a normal process, and some of the species on the Henry’s Fork actually propagate in this way.
Aquatic vegetation at the Island Park stream gage reaches its peak for the season during the later summer/early fall. During this time, the vegetation begins to die and move out of the channel. That means that for the remainder of the fall, the gage will read slightly lower than the “actual” flow in between rating adjustments. Flow adjustments take place approximately every 6 weeks.
Once the macrophytes are gone, there is a limited window of time when the river can be scoured of fine sediment (March, April, May, June). The solution is to run a spring freshet (rush of fresh water at ~2,000 cfs) to help export this sediment.
For more information regarding the April 2023 spring freshet, check out HFF’s water quality website: https://henrysforkdata.shinyapps.io/Freshet2023/
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
