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Island Park Reservoir is a man-made reservoir in Fremont County, Idaho, USA. It was created by
constructing a dam in 1938 on the Henrys Fork of the Snake River near the headwaters. The Henry’s
Fork is the primary inflow to Island Park Reservoir, making up approximately 60% of the total inflows to
Island Park Reservoir in an average water year. 53% or 675 km2 of the reservoir’s watershed drains
through the Henry’s Fork; the remainder of the reservoir’s watershed drains through Sheridan,
Icehouse, Hotel, Blue, Sheep, Dry, Elk Springs, and Mill creeks, as well as through local runoff. The vast
majority (80%) of the watershed comprises undeveloped forest and shrublands. About 70% of the
watershed is federally-owned, and about 15% is state-owned. The remaining ~15% is private. Of these
private lands, the majority are large rural tracts used for grazing. Island Park Reservoir is not your
typical, deep canyon western impoundment. Much of the 8,000 acres of the reservoir is contained in the
shallow west end.

To address persistent water quality concerns, the Henry’s Fork Foundation (HFF) along with Idaho Department of Fish and Game and partners have launched the “Developing Infrastructure to Reduce Temperature and Turbidity” (DIRTT) project. The DIRTT project aims to tackle challenges in the Henry’s Fork Watershed: high water temperatures, high turbidity, low dissolved oxygen, and harmful algal blooms (HABs). Water quality problems arise due to eutrophication in Island Park Reservoir, aging and outdated infrastructure at Island Park Dam, degraded tributaries, and drought. The DIRTT project will develop implementable 60% design plans, fill data gaps, and engage stakeholders regarding the watershed

The Henry’s Fork Foundation’s DIRTT project at Island Park Reservoir will address the following: create additional summer habitat for kokanee salmon and other trout, reduce the prevalence of harmful algal blooms (HABs) within the reservoir, and limit the transport of turbid water in the Henry’s Fork below Island Park Dam while also cooling summer temperatures in the river. Eutrophication of the reservoir, degraded tributaries to the reservoir and the river, and increasing temperatures are all issues that must be addressed.

Island Park Reservoir’s primary purpose is to provide irrigation water for downstream agricultural use. The reservoir stores water during the winter and spring months when there is a surplus, which is then released during the drier summer and fall months to support crop growth. Fremont-Madison Irrigation District represents the local water rightsholders who hold rights to water stored in Island Park Reservoir. The U.S. Bureau of Reclamation manages Island Park Dam in concert with other USBR and non-USBR irrigation storage facilities in the Upper Snake River, including Palisades Dam, Jackson Lake Dam, Grassy Lake Reservoir, Ririe Reservoir, Lake Walcott, Milner Reservoir, Henrys Lake Reservoir, and American Falls Reservoir. Releases from Island Park Reservoir are meant to work within the context of the entire system to benefit irrigation water rightsholders along with secondary goals of maintaining public recreational opportunity, flood control, and power generation.
Water quality is a key limiter of fish habitat and fish populations in the Henrys Fork Watershed upstream of Mesa Falls, in particular the three HUC-10 watersheds Henrys Fork/Buffalo, Island Park Reservoir, and Sheridan Creek. Water quality also affects fish behavior, aquatic insect behavior, and thereby the fishing experience in Island Park Reservoir and the Henry’s Fork downstream. High water temperatures, harmful algal blooms (HABs), high turbidity, and low dissolved oxygen levels are key water quality issues that impact fisheries and aesthetic resources in the Henry’s Fork watershed. These problems threaten a world-famous recreational fishery worth at least $30 million (Grunder et al. 2008, Loomis 2006), prevent the restoration of recreationally and ecologically significant populations of migratory kokanee salmon and native Yellowstone cutthroat trout, reduce hydropower generation by Fall River Rural Electric Cooperative, and potentially affect tens of millions in property values on Island Park Reservoir and the Henry’s Fork River. Friends of Reservoirs has provided a $50K grant through the USFWS to assist with the precursor to DIRTT – Stopping the Squeeze, Scoping hypolimnetic oxygenation for water quality and fish habitat in Island Park Reservoir, Idaho. This work, which involves developing a hypolimnetic oxygenation design plan and conducting outreach and education within the local community, can be considered the first step of DIRTT and is currently underway.

The DIRTT project will develop implementable 60% design plans, fill data gaps, and conduct stakeholder engagement to support:
1. An oxygenation project on Island Park Reservoir to break the cycle of eutrophication
2. A variable-elevation outflow system to address aging infrastructure and help prevent the movement of poor-quality water in Island Park Reservoir into the Henry’s Fork River downstream
3. Restoration projects on key tributaries in Harriman State Park and around the reservoir to increase refuge habitat for coldwater fish and wildlife in the Henry’s Fork

An oxygenation system would increase kokanee habitat in Island Park Reservoir by thousands of acre-feet, and increase in Yellowstone cutthroat trout and rainbow trout habitat by tens of thousands of acre-feet. The potential to increase fish habitat and restore populations of migratory fish is tantalizing: spawning runs enhance angling opportunities and enrich the local ecosystem by providing an important food resource for charismatic and threatened terrestrial and avian predators such as Grizzly Bears, Ospreys, and American White Pelicans. Improved food resources for Grizzly Bears may reduce conflict with humans, and increased runs of Yellowstone cutthroat have been shown to reduce Grizzly predation on elk calves.
Second, funding will provide 60% of the design plans for implementing a variable-elevation outflow system. This system would enable managers to withdraw water from specific reservoir layers, allowing them to improve water quality by reducing the movement of poor-quality water into the Henry’s Fork downstream. During a density current (common in the late summer/fall), managers could select higher elevations to draw from in the reservoir to avoid the sinking plume of turbid water. If and when oxygenation cannot prevent water quality issues in Island Park Reservoir, a variable-elevation outflow gate would contain water quality problems within the reservoir, thereby improving water quality downstream.
Third, the DIRTT project will work synergistically with HFF’s ongoing efforts to improve water quality by addressing drought, including HFF’s Farms and Fish and Precision Management initiatives. The DIRTT project will enhance the resilience of aquatic ecosystems through planned tributary restoration.

Recreational use is heavy in and around Island Park Reservoir. Power boating, swimming, and fishing are common activities. Island Park Reservoir and its tributaries are a popular recreational angling location, especially for families, helping make the Henry’s Fork the most popular fishery in Fremont County and supporting a local fishing-based economy worth around $30 million (Grunder et al. 2008, Loomis 2006). The fishery has declined since the 1980s when Idaho Department of Fish and Game (IDFG) data indicates it was a fishery of significant state interest and likely greater economic impact due to good catches of large rainbow trout cutthroat trout, and kokanee salmon (High et al. 2015, Flinders et al. 2016). Management priorities include restoring the fishery to its former status and reducing uncertainty, as increased temperatures and drought frequency create a concomitant increased need for water, thereby increasing the likelihood of excessive drawdown (High et al. 2015, Flinders et al. 2016).
An increased awareness and prevalence of harmful algal blooms (HABs) threaten swimming and other primary contact recreation. HABs also threaten power boating and may create problems. Understanding the trade-offs among different recreational uses will be important for intelligent, adaptive management in the future.

Island Park Reservoir contains many anglers’ favorite fish, including kokanee salmon, rainbow trout, Yellowstone cutthroat trout, and brook trout. Supplemental stockings have played a significant role in managing the reservoir fishery. However, spawning and wild recruitment by all species occur in the Henrys Fork Snake River upstream of the reservoir. IDFG stocks approximately 250,000 fingerling kokanee, 150,000 catchable triploid rainbow trout, and 30,000 fingerling Yellowstone cutthroat trout annually. Stockings resulted in a self-sustaining kokanee population, which spawn in Moose Creek. Decades ago, IDFG established a kokanee trapping facility on Moose Creek to collect eggs for stocking in other waters. The Moose Creek kokanee trap was operated intermittently from the 1960s through the 1990s, with over 5 million eggs collected in 1969, and over 200,000 eggs collected in 1995. Trap operations after 1995 ceased due to low returns. The loss of the kokanee salmon resource in Island Park Reservoir greatly reduced the resiliency of the IDFG kokanee salmon conservation and stocking program.
Kokanee in Island Park Reservoir are still stocked, but stocked fish do not appear to recruit in high numbers into the fishery. Kokanee runs are measured in the thousands instead of historical runs in the tens of thousands. Most kokanee spawn in the Henrys Fork and Henrys Lake Outlet. Almost all kokanee that return to spawn are of wild origin. Kokanee salmon recruitment appears to be control

• Kokanee Salmon
• Yellowstone cutthroat trout
• Brook trout
• Rainbow trout

• Excessive nutrients
• Algae blooms
• Anomalous water regime
• Large water fluctuations

• Magnuson-Stevens Fishery Conservation and Management Act
• State Wildlife Action Plan

DIRTT requires the development of a water quality basin plan that features collaboration with stakeholders within the Henrys Fork Watershed over two years to identify critical issues of concern, identify potential infrastructure or restoration actions, collect engineering and ecological data to understand costs and benefits, and develop and evaluate design plans for implementation. A collaborative, evidence-based evaluation process will increase the likelihood of implementation and subsequent water quality, fisheries, ecological, and economic benefits.
DIRTT also requires closing essential data gaps to 1) support stakeholder engagement, 2) address stakeholder concerns, and 3) obtain necessary data and information to produce accurate design plans. We propose to fill these data gaps through a combination of contracted activities with external consultants and in-house data collection and analysis.
Stakeholder outreach and collaboration will drive the development of infrastructure and restoration alternatives, analysis of costs and benefits, and final project rankings and evaluation for implementation. At the highest level, stakeholders fall into two general categories: 1) agencies and engineering/natural resource professionals and 2) community members.
All of the potential types of reservoir treatments, infrastructure upgrades, nature-based restoration, and aquifer recharge activities mentioned in this application and considered by the HFF to date have been successfully appl

A water quality basin study intends to take the next logical step to buffer water quality and subsequent fish and macroinvertebrate habitat from climate change and drought by identifying, designing, and evaluating for implementation a wide variety of water quality improvement projects aimed at aging and inflexible physical and natural infrastructure in Island Park Reservoir and degraded tributaries throughout the watershed. This will produce projects such as a hypolimnetic oxygenation system and a variable–elevation outflow system, which could increase fish habitat in Island Park Reservoir by 350% and permanently enhance deep, cold-water refugia despite climate-driven uncertainty. This project will be successful if HFF and partners have a clear plan, supported by data and analysis, to implement infrastructure that resolves temperature and turbidity issues within the Henry’s Fork watershed and Island Park Reservoir.

Outreach for this project will be conducted through the Henry’s Fork Watershed Council and special DIRTT sub-groups, which will benefit from professional facilitation. The progress and achievements of the DIRTT project will be shared through various media, including social media platforms such as the Henry’s Fork Foundation’s Instagram and Facebook sites, the HFF website, monthly emails, and newsletters. Partners such as Idaho Fish and Game will also share the progress of the DIRTT project with their constituents. HFF has an email list of over 4,000 individuals.

Results will be shared through Henry’s Fork Watershed Council meetings, a presentation to the Idaho Water Resource Board, an IDFG project report, and reports to the US Bureau of Reclamation Water SMART program. The final report crafted by HFF will serve as the template for implementation and the key fundraising tool to build the infrastructure necessary to ensure the health of the Henry’s Fork watershed and Island Park Reservoir into the future.

1) Address water quality problems caused by aging and inflexible physical and natural infrastructure at Island Park Reservoir through projects such as variable-elevation withdrawal gates, hypolimnetic oxygenation, algaecides, water column nutrient management, sediment stabilization, sediment removal, and/or a watershed sediment and nutrient control plan.
2) Restore degraded surface and groundwater inputs to Island Park Reservoir and the Henrys Fork with nature-based stream, wetland, and shallow aquifer restoration projects implemented throughout the project watershed.
3) Accomplish with facilitated public input and finish with a 60% design plan that meets the needs of USBR WaterSMART funding, is ready for implementation, and can be presented to the Henry’s Fork Watershed Council and Idaho Water Resource Board.

Please limit your proposed budget amounts to the grant period. You are responsible for accounting for the Non-Federal match as part of grant completion.

Note: Based on 2022 Bureau of Labor Statistics, Biological Scientists in State government made an average of $33.23/hr. Volunteers are often valued at $29.95/hr.

See attached project application file.

Idaho Fish and Game is the state agency partner designated in HFF’s WaterSMART grant and is a member of the HFWC.

• Support-Letter_IDEQ.pdf
• Support-Letter_FRREC.pdf
• Support-Letter_IDPR.pdf
• Support-Letter_IDPR-Copy.pdf