The Snake

The Snake River, the longest tributary of the mighty Columbia, is a critical stronghold for fall Chinook. Managing actions to protect and restore the river’s health is no small undertaking. Add into the mix a series of dams along the Hells Canyon that generate clean hydropower but present obstacles to fish and water conditions.

“It’s clear that to improve conditions downstream, we have to start improving conditions upstream,” said David Primozich, vice president of water. “Stopping excess sediment and nutrients from getting into the river, and reducing high water temperatures, are key.”

It’s this long arc toward restoration that TFT is on. More than a decade ago, we began collaborating with Idaho Power Company to put in motion a comprehensive plan to recover water quality in this critical Pacific Northwest watershed. There were some large gears to move, including quantifying thermal benefits from recovering streamside shade and improving conditions in the main channel, while also securing agreement from multiple regulatory agencies on a new approach. We are extending the earlier momentum we created in Oregon around water quality trading into Idaho

“Change happens when we partner with the right people in the right place. Working together, we pull the levers that shift the momentum of restoration,” said Primozich.

In the decade of working with IPC, we’ve also collaborated with others along the Lower Boise River, a tributary of the Snake. Between 2013 and 2015, we completed field-level assessments for sediment reductions, jointly funded by four cities and two corporations. While this collaboration set the stage for a trading framework in Idaho, the regulatory permits have long timelines. But interest is growing. In fact, in 2021, the state of Idaho passed legislation that encourages water quality trading alternatives in municipal discharge permits.

Using Data to Drive New Programs

IPC’s $350 million Snake River Stewardship Program is a catalyzing force in the basin. While in its pilot phase, which began in 2016, the program has enhanced eight acres of floodplains, planted 37,000 native trees and shrubs, and prevented 1,900 tons (nearly 4 million pounds) of sediment and 2,950 pounds of phosphorus per year from washing off fields into the river. Further riparian restoration and instream work is slated to accelerate over the next few years as the program transitions from pilot phase to full implementation.

“Hundreds of riparian revegetation projects will be implemented as part of the SRSP,” said Olivia Duren, environmental quality program manager. “Some of these projects will be intensively monitored. A vegetation monitoring selection tool we’ve developed provides a robust way to objectively select the right number and types of projects to monitor so that their results are representative and useful for assessing the program’s success.”

Building the management systems and tools for the SRSP has a broader effect. The tools are deployed and tested first in one project area, such as the Snake, and then ripple out to allow us to use the tools with partners in other basins. The impact of innovations driven by the SRSP is multiplied.

In 2020, TFT began collaborating with IPC on a second program along the mid-Snake to assess the potential to reduce phosphorus loads that cause algae blooms in reservoirs. Using TFT analytics, high-efficiency projects can be identified and grouped into cost-optimized portfolios that meet sediment and nutrient reduction targets. These nutrient loads exacerbate the methylation of mercury that can ultimately make fish unhealthy to eat. IPC will use this analysis to work with regulators and stakeholders to drive new data-driven programs for the watershed.

“Improving water quality in a system as big as the Snake River requires watershed-scale efforts across a broad range of stakeholders,” said Brett Dumas, environmental affairs director at Idaho Power. “The Snake River is the cornerstone of southern Idaho’s culture, communities, and incredible natural resources. Working together with groups like TFT who share a common vision for sustainable, holistic solutions will ensure the Snake River remains a valuable resource for future generations to come.”

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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 were 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 were 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.