Watershed Council Tours Island Park Reservoir - Henry's Fork Foundation

Watershed Council Tours Island Park Reservoir

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Thank you to all of those who attended this year’s annual Henry’s Fork Watershed Council tour! Participants toured the Last Chance Wastewater Treatment Plant, Island Park Reservoir, and Island Park Dam. A special thank you to Fremont County, the City of Island Park, Forsgren Associates, Fall River Rural Electric Cooperative, and Fremont-Madison Irrigation District for sharing their knowledge on some great new projects in our watershed–like the DIRTT Plan and Last Chance WWTP upgrades.

Learn more about the Watershed Council here.

Learn more about the DIRTT Plan here.

Learn more about how Island Park Dam works and how it’s managed.

Learn more about Last Chance WWTP here.

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Recent Posts

Recent Posts

An aerial view of Island Park Dam. The reservoir sits behind it and the river flows below it.

Water Quality

Summer 2026 Water Quality Forecast for Island Park

This article was originally published in Island Park News on May 29, 2026 Ice melted on Island Park Reservoir on March 31, 2026—four weeks earlier than normal and the earliest the Henry’s Fork Foundation (HFF) has observed in 12 years of monitoring. Such an early ice melt was not unexpected given the region’s near-record warm and dry winter. But ice melting a month early has implications for water quality in Island Park Reservoir and the

Christina Morrisett May 28, 2026

Aerial photo of Island Park Reservoir. The dam is in the bottom left corner. The Centennial Mountain Range is in the top.

Research and Monitoring

History of Water Quality in Island Park Reservoir

Warmer and drier conditions have slowly degraded water quality in Island Park Reservoir over the last 50 years. In the 1970s and 1980s, federal reports and university research indicate that the reservoir had relatively good water quality. Island Park Reservoir was mesotrophic—with mostly clear water and occasionally low dissolved oxygen at the reservoir’s deepest depths during the summertime. But, as time went on, water quality began to decline. Historical satellite imagery analyzed by the U.S.

Christina Morrisett May 22, 2026

A photo taken of Island Park Reservoir while standing on the dam and looking north. The sky is cloudy, Mt Sawtelle sits with little snow in the background, and the reservoir is open water (save for a few small sheets of ice in the distance).

Frequently Asked Questions

Reservoir Ices Off, Growing Season Turns On

Photo of an ice-free Island Park Reservoir taken on March 31, 2026 On March 31, 2026, with no accompanying commentary, HFF scientist Christina Morrisett stood on top of Island Park Dam and texted colleagues Rob Van Kirk and Jack McLaren photos of open water on Island Park Reservoir. Rob, eager to see that the reservoir reality matched what he was seeing in the real-time river data downstream, texted back, “Yep! That’s close enough to ice

Christina Morrisett May 7, 2026

Photo of confluence of Warm River and Henry's Fork

Fisheries

Water Supply and Water Quality Predictions for Summer 2026

The photo above captures the unprecedented situation we face at the beginning of April. The photo, of the confluence of Warm River and the Henry’s Fork, was taken on February 7 and shows the shocking lack of snow we experienced in the watershed all winter as a result of record-breaking warm temperatures. How will the warm winter and lack of snow affect water supply, water quantity, and fisheries? The highlights are below. If you want

Rob Van Kirk April 10, 2026