This story was written by Audrey Hunter (2026 intern) and was originally published in the Fall 2026 Newsletter.
It’s no secret that late summers on Island Park Reservoir haven’t been in perfect conditions in recent years. Warm, turbid, algae-filled water plague reservoir recreationists while diminishing water quality downstream. Cyclical algal blooms decrease water clarity and create less-than-ideal circumstances for the reservoir’s flora and fauna. What’s the solution? HFF’s DIRTT Plan.
Nutrients released from reservoir sediment fuel algal blooms. Since sediment releases fewer nutrients in oxygenated water, oxygenation is incredibly effective in reducing algae blooms. Without algae, water clarity improves greatly in the reservoir and the Henry’s Fork downstream. By installing infrastructure at the bottom of the lake, we can bring oxygen bubbles directly to where they’re needed most.
In summer and fall, oxygen levels in the reservoir frequently get low enough that habitat is diminished—not only for fish, but for zooplankton that feed on algae. In-reservoir oxygenation works year-round to maintain an oxygen-rich bottom layer that supports these algae-eating zooplankton.
Oxygenation increases water clarity in the Henry’s Fork, improving your fishing experience, but it also provides the foundation for a healthier reservoir. Oxygenation could dramatically increase fish habitat—by up to 350%. Fewer algal blooms allow rooted aquatic plants to grow, stabilizing bottom sediments, absorbing nutrients, and creating clearer water.
We’re working with HDR and J-U-B Engineers to understand the cost and feasibility of reservoir oxygenation in Island Park Reservoir. Oxygenation is just one part of our vision. We’re committed to finding the most effective solutions to the reservoir’s biggest problems.
Learn more at https://henrysfork.org/dirtt-plan/.
Our Aquatic Ecology Program Manager, Dr. Jack McLaren, joined Idaho Falls city and FIPS-Mouche leadership at the opening ceremony parade along the Snake River Greenbelt to welcome competitors to the watershed and to make sure conservation was front and center.
Drone photo of Island Park Dam taken on September 9, 2026 Looking Back on September September brought lows and highs to Island Park. Island Park Reservoir started September at 29% full and quickly fell to a low of 12% full on September 19. The rapid drawdown of the reservoir was the result of managers needing to move water downstream to American Falls (to irrigate farms in the Magic Valley with senior water rights). Such low
This story was written by Audrey Hunter (2026 intern) and was originally published in the Fall 2026 Newsletter. It’s no secret that late summers on Island Park Reservoir haven’t been in perfect conditions in recent years. Warm, turbid, algae-filled water plague reservoir recreationists while diminishing water quality downstream. Cyclical algal blooms decrease water clarity and create less-than-ideal circumstances for the reservoir’s flora and fauna. What’s the solution? HFF’s DIRTT Plan. In-Reservoir Oxygenation Nutrients released from
Drone photo taken on September 9, 2026 The Henry’s Fork Drought Management Planning Committee met on Wednesday, September 16 2026 to develop an updated reservoir management strategy. Downstream of the Henry’s Fork watershed, lower-valley irrigation demand over the rest of the season is anticipated to be slightly lower than projected last week, so Island Park Reservoir and Grassy Lake (in the Fall River drainage) do not need to deliver any more water out of the
