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.