The Snake

The Problem We Are Solving

The Snake is among the hardest working rivers in America. It supplies electricity for dozens of communities, habitat for fish and waterfowl, and water for nearby farms and ranches, and shows thousands of recreationalists a good time. As the climate changes, these pressures will be exacerbated. Much of the middle section of the Snake in southwest Idaho has been degraded. Long lengths of bare streambanks are exposed to the unforgiving Idaho sun and sediment moves easily from land to water, impacting water quality and habitat. As sediment accumulates, the river has become shallower and water moves slowly, creating ample footholds for unwanted weeds. In partnership with Idaho Power Company, TFT is replanting key tributaries while also deepening the main river channel and enhancing natural floodplains to improve water quality, velocity and fish habitat.

The Full Story

At 1,078 miles long, the Snake is the largest North American river emptying into the Pacific Ocean and the largest tributary of the Columbia River.

It’s been used to generate hydropower since 1900, and today, more than 500,000 customers rely on it for electricity. The river also supports vibrant agricultural and recreation communities and salmon, steelhead and white sturgeon populations.

As part of the federal process for relicensing its three-dam Hells Canyon Complex, Idaho Power is mitigating the effects of the Hells Canyon Complex on late summer and fall water temperatures. Warm water from the watershed collects in Brownlee Reservoir and flows out of Hells Canyon several degrees warmer than current state and federal standards allow. Idaho Power has considered numerous options to meet temperature requirements.

Working with The Freshwater Trust, Idaho Power is proposing a restoration program intended to decrease thermal loading to the river upstream of the Hells Canyon Complex and to provide widespread environmental benefits for native species such as the Snake River Physa (an endangered snail), white sturgeon and mountain whitefish.


“The Freshwater Trust provides experience with developing and implementing watershed restoration programs within the regulatory framework of the Clean Water Act,” said Ralph Myers, Environmental Supervisor with Idaho Power Company.

Using modeling, satellite imagery and 21st century technology, The Freshwater Trust is able to quantify the impacts of natural infrastructure. As an example, the amount of sunlight blocked by a tree planted on a riverbank can be calculated, allowing for an action like planting trees to be weighed as a viable option for compliance with state-regulated total maximum daily temperature loads for a river. This approach, defined by The Freshwater Trust as Quantified Conservation, is a method of using data and technology to ensure that every restoration action has a positive outcome for the environment. It’s about leveraging the best practices used by businesses and social sector organizations to restore the state of the natural environment.

Planting native vegetation along key tributaries to the Snake River, collaborating with irrigators to reduce agricultural runoff, enhancing floodplains and wetlands associated with the river bank and existing islands, and even creating new islands in the Snake River are all part of the proposed stewardship plan for the Snake River watershed.

Bayha Island floodplain enhancement

Aerial imagery by Idaho Power

“A watershed restoration program will improve temperature and habitat conditions throughout the area of implementation,” said Myers. “The program is a way to allow stakeholders to work together to improve water quality at a scale that will be meaningful to natural resources.”

Over time, the instream restoration projects and streamside revegetation projects will reduce the thermal load to the Snake River by 15 billion kilocalories every day.

“Our ability to identify the true outcomes of a restoration project and assign a value to nature allows us to bring another option to the table,” said Alex Johnson, Freshwater Fund Director with The Freshwater Trust.

“The Snake River is not functioning like it is supposed to, and we’re presenting an option with benefits that extend far beyond just allowing Idaho Power to obtain relicensing.”

New wetlands, cooler water temperatures and native vegetation would improve habitat for fish, birds and other wildlife calling the area home.

“Idaho Power is most excited about being able to implement a program that will result in environmental benefits in a way that also benefits local communities, other stakeholders, our customers and shareholders,” said Chris Randolph, Environmental Affairs Director with Idaho Power Company (now retired). “It could serve as a model for future environmental enhancement and mitigation efforts that over the long-term could result in meaningful changes to the quality and function of the Snake River.”

Instream restoration work in the Middle Snake River could span a 30-mile reach of the river that still supports remnant populations of native species such as white sturgeon and Physa snails and was historically used by fall Chinook salmon for spawning and migration. Riparian revegetation projects on 10 key tributaries could cover more than 150 miles.

An extensive permitting and review process must be completed before the work takes place. Idaho Power and The Freshwater Trust have conducted preliminary assessments to establish the feasibility and effectiveness of different aspects of the program.

“Being able to provide a high level of certainty and transparency to the proposed program has changed conversations with regulators,” said Randolph. “It has allowed regulators to gain a level of definition and certainty necessary for them to be more creative in their thinking relative to mitigation options.”

Oregon Department of Environmental Quality and Idaho Department of Environmental Quality issued certifications for the program in 2019, including a wholesale incorporation of the Snake River Stewardship Program.

“The Freshwater Trust provides perspective to the requirements and necessary components of a watershed restoration program that can be supported by stakeholders with environmental priorities,” said Myers. “Their abilities to develop and plan watershed restoration on a large scale, coupled with IPC’s research and implementation capabilities are very complementary in developing and implementing a large, landscape-scale watershed restoration program with this level of compliance accountability.”

How We Are Solving It

Work on the Idaho Power Company’s Snake River Stewardship Program commenced in 2016, and building new relationships and projects in new places was a highlight of 2018.

TFT worked in tributaries of the Snake, along the Weiser and Little Weiser Rivers. Riparian vegetation, such as native black cottonwood, willows and dogwoods, were planted in five to 250-foot buffers along the streambanks. Historically, these channels were altered in an effort to protect against flooding and to provide irrigation water to agricultural lands. Replacing the tree canopy now will reduce the amount of solar radiation reaching the river and promote the natural biological processes that will improve water quality.

We implemented a research experiment on the Little Weiser site to compare the performance of vegetation in actively versus passively restored areas. Implementation with active restoration uses a combination of weed removal, planting, fertilization, wildlife browse protection and weed barrier methods. Maintenance actions include livestock exclusion fencing, irrigation and weed treatment. Passive restoration actions are simpler and focus on removing the primary disturbance that prevents the area from recovering on its own. In this case, fencing was installed to temporarily remove cattle, and weed treatments suppress noxious weeds that compete with native plants.




Maintenance and monitoring also continued at previously installed sites on Bayha Island and along the banks of the Powder River. Despite being inundated with spring flows of up to 30,000 cubic feet per second for two years in a row, the new plants on Bayha are thriving, with some trees as tall as 15 feet already.

The Hells Canyon hydropower complex is the backbone of Idaho Power’s clean energy portfolio. We’re working toward a solution that keeps clean energy in play while also improving an impacted river system.

Interested in reading more about the Snake River Stewardship Program?

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A hydropower dam is initially licensed by the Federal Energy Regulatory Commission (FERC) at the time of construction, it must then be periodically relicensed for continuation of the existing project. One component of the licensing/relicensing process is an examination of the potential environmental impact of the dam on the river ecosystem and function, and a mitigation plan to address any impacts. As part of the relicensing of the three-dam Hells Canyon Complex, Idaho Power Company plans to implement the Snake River Stewardship Program (SRSP), a watershed-scale restoration plan for offsetting temperature impacts.

Section 401 of the federal Clean Water Act requires state certification for a license issued by a federal agency for an activity that may result in a discharge into waters of the U.S., such as a hydropower dam. This requirement allows each state to have input into federal projects that may affect its rivers and streams and to ensure the projects will comply with state water quality standards. For the Hells Canyon Complex, both Idaho and Oregon Departments of Environmental Quality must review and grant 401 certification.

Oregon and Idaho Departments of Environmental Quality jointly set water quality targets for the 2,500 square miles of the impaired Snake River-Hells Canyon subbasins. The Snake River-Hells Canyon Total Maximum Daily Load (TMDL) contains temperature load allocations for point sources and nonpoint dischargers, like the Hells Canyon Complex. The load allocation assigned to the Hells Canyon Complex is exceeded during the fall; Idaho Power must address elevated water temperatures below Hells Canyon Dam. An increased thermal load in the water can negatively impact the rearing and spawning habitat of cold-water fish. In order to offset its portion of the heat load in the TMDL, Idaho Power will implement the multi-project SRSP as part of a Temperature Management and Compliance Plan. Meeting the requirements of the Snake River-Hells Canyon TMDL for temperature is part of Section 401 certification.

The Shade-a-lator module, a unit of the HeatSource model, is used to calculate temperature improvements as a reduction in thermal loading from the sun to the river due to riparian (streamside) vegetation. Riparian trees block the sun, increasing the shading of the stream. Riparian revegetation creates thermal improvement that are quantified in units of kilocalories per day. Riparian revegetation projects are proposed for more than 100 miles of streambank along 10 tributaries of the Snake River. The proposed riparian revegetation projects will restore many of the natural riparian functions that are currently missing from the Snake River tributaries. Over time, these revegetated riparian areas will not only shade the streams, but will also contribute large wood and other organic material to the stream, stabilize streambanks, increase cold-water patches, and increase water storage.

Geospatial analysis and existing models are used to calculate temperature improvements as a reduction in thermal loading from changes in river surface area. These actions create thermal improvements that are quantified in units of kilocalories per day. The proposed instream actions will increase sinuosity and complexity of the shallow, slow-moving Snake River. Actions at multiple project sites include narrowing and deepening the river channel by enhancing floodplains and wetlands and constructing or enhancing islands. Constricting the width of the channel will increase water velocities and sediment transport along the riverbed around the project sites. This in turn will help to keep the gravel riverbed free of fine sediment – good for both cold-water fish habitat and hyporheic exchange. Hyporheic exchange refers to the mixture of water in the river channel with adjacent shallow groundwater, creating cold patches in the river.

In addition to instream and riparian improvement projects for temperature, the SRSP includes a third set of actions to address sediment and phosphorus transport. By upgrading to pressurized irrigation systems in relevant upstream agricultural areas, sediment and phosphorus runoff from agricultural land practices will be reduced. These voluntary reduction actions would protect the ongoing effectiveness of the instream restoration projects in downstream reaches of the Snake River.

Yes. The area is home to numerous sensitive species, including trout, whitefish and sturgeon, as well as the endangered Physa snail. The Mid-Snake River suffers from various issues that compromise water quality and wildlife habitat. These include: lack of streamside vegetation; slow-moving water due to wide, shallow channels; nutrient and sediment loading from agricultural runoff; excess aquatic vegetation growth; and low oxygen levels. Restoring the river’s natural functions will have a significant positive impact for native species.

The proposed watershed restoration program will have widespread environmental benefits in the Snake River and tributaries. Conversely, a structural solution such as a temperature control structure (TCS) in Brownlee Reservoir, an alternative that has been proposed by other stakeholders, would provide no upstream benefits, limited downstream benefits for temperature, and could adversely impact downstream resources.

The SRSP is designed as a compliance program for 401 certification of Idaho Power Company’s Hells Canyon complex. It will extend for the term of the new license, which is expected to be 40 to 50 years, and address water temperature issues and river-channel function between the Hells Canyon Complex and Swan Falls Dam.

There are three components to the SRSP.
1. The instream restoration actions, including narrowing and deepening the river channel, and creating inset floodplains and emergent wetlands will be located in the Middle Snake River from Walters Ferry to Homedale. The first construction actions will take place around Bayha and Wright Islands.
2. The riparian habitat improvement actions, including restoring native vegetation for shade along key streambanks, will take place along 100 miles of 10 major tributaries of the Snake River. The first plantings will likely take place in the Powder River subbasin.
3. The upland irrigation improvement actions, including implementing best management practices for irrigation, will take place numerous locations along the Snake River where agricultural runoff is a significant contributor to poor water quality. The first upgrades are taking place in the Grand View area.

Yes. The stewardship program will create a river channel with sections that are deeper and have faster-flowing water, to inhibit the growth of unwanted aquatic plants and provide better cold-water conditions for fish. The associated wetlands and floodplains that will be created will enhance wildlife and bird habitat. When completed, the channel modifications will make it easier for boat navigation in the Middle Snake River, and public land will remain accessible.