Six Things to Know about the Potter Valley Project and Eel River Restoration
Since CalTrout’s inception 50 years ago, we have worked tirelessly to protect and restore the Eel River. This remarkable river, the third largest in California, holds immense potential to recover a harvestable population of wild salmon. These salmon have long served as an economic driver on the North Coast and have been vital to the communities that have lived near the river for thousands of years.
As PG&E moves forward with its plans to remove Scott and Cape Horn dams as part of its decommissioning of the Potter Valley Hydroelectric Project, here are six things to know about how and why this is happening.
1. PG&E is removing the dams for economic reasons
Economic factors are often the primary drivers behind dam removal decisions in the United States. While ecological restoration and public safety also play a role, the financial burden of operating aging dams frequently leads dam owners to choose removal. Old hydropower dams tend to be inefficient at producing electricity and are an expensive liability for the companies that own and operate them. Coupled with decreasing costs for other forms of renewable energy, companies are more likely to seek alternatives to hydropower.
In 2019, PG&E announced it would not renew its federal license to operate the Potter Valley Project. For those of us paying attention, it was not a big surprise. For nearly a decade, PG&E has considered the Project uneconomical for its customers.
PG&E has provided two public drafts of its decommissioning plan and will submit the final plan and surrender application to federal regulators in July of this year. This will initiate the public regulatory process, including the creation of detailed management plans for removing the dams and restoring the lands affected by the facilities.
In the years since PG&E made its decision, additional factors have emerged that further illustrate the challenges of operating the aging dams. These include sediment buildup behind Scott Dam, which poses a risk of clogging the low-level outlet; new seismic information from 2023 that led PG&E to reduce storage in the reservoir to mitigate the risk of earthquake damage; and the failure of the transformer in the powerhouse in 2021, which halted power generation.
All of these factors show that removing the facilities is in the best interest of PG&E’s customers and our energy bills.
2. Local groups are collaborating to support a modernized water supply
Along with producing hydroelectric power, the Potter Valley Project transfers water from the Eel River to the Russian River. PG&E owns and operates the Potter Valley Project for electricity generation, but water users downstream of the powerhouse in the Russian River have capitalized on the supplemental water transferred by PG&E. With PG&E surrendering its license to operate the facilities, there will no longer be an entity to own and operate the diversion into the Russian River. PG&E is not obligated to continue the water transfer.
Recognizing regional concerns about the water supply, PG&E made several efforts to enable a new owner to take over the facilities. Ultimately, no one stepped forward. Federal regulators then required PG&E to develop a surrender application and decommissioning plan.
CalTrout collaborated for several years with local water managers, the Round Valley Indian Tribes, and other groups to explore alternatives for sustaining the Project’s water supply benefits. This included examining fish ladders and other methods for facilitating fish passage around the dams. In a recent op-ed, local water managers clarified that maintaining the existing dams was neither financially nor operationally feasible. Ultimately, our work indicated that dam removal, combined with a wet season water diversion, represented the most viable path forward.
During PG&E’s development of its decommissioning plan, the Eel-Russian Project Authority (ERPA)—comprised of Sonoma Water, the Mendocino County Inland Water and Power Commission, and the Round Valley Indian Tribes—proposed building a new diversion near Cape Horn Dam. At the Round Valley Indian Tribes’ request, Humboldt County, the California Department of Fish and Wildlife, Trout Unlimited, and CalTrout were invited to participate in negotiations regarding the terms of a future diversion to ensure it would not interfere with the recovery of the Eel River and its fishery.
ERPA’s proposal supports PG&E’s removal of the Scott and Cape Horn dams. It allows ERPA to take over key facilities like the diversion tunnel and construct a modern, reliable, fish-friendly diversion facility at the site of the Cape Horn Dam to ensure the continued transfer of water to the Russian River. This facility will provide a more secure water supply for the region than the aging dams. PG&E is working with ERPA to plan the new diversion facility.
3. Local economies are expected to benefit from dam removal
Removing Scott and Cape Horn dams and building a new diversion will be a major local construction project. According to a 2022 report from The Bay Area Council Economic Institute, the work is expected to generate $252 to $345 million in economic output and support between 1,223 and 1,637 full-time job-years (a job-year is a full-time equivalent job for one year) based on early estimates of project costs. Most of these benefits will be concentrated in Lake and Mendocino counties, boosting local employment and providing economic gains for the region. This is in addition to the water supply benefits of the project, which would continue to support agriculture and communities in Mendocino and Sonoma counties.
4. Removing the dams will support salmon recovery
Scott and Cape Horn dams are not the only factors contributing to the decline of Eel River salmon and steelhead, but working to recover salmon without removing the dams is akin to fighting with one hand tied behind your back. Scott Dam blocks a nearly 300-square-mile watershed, an area comparable to a medium-sized coastal river such as the Gualala River or Redwood Creek. This diminished capacity for salmon production in the Eel River significantly complicates recovery efforts, particularly given the high-quality habitat above the dams.
Simply put, no single action in the Eel River would benefit Chinook salmon and steelhead recovery more than dam removal. The headwater reaches of the river provide some of the highest quality habitat in the basin, including cold water that is crucial for the survival of juvenile steelhead trout during the warm summer months. For Chinook salmon, which migrate out to the ocean during the first spring after they hatch, the area above the dams offers 89 miles of spawning habitat, which was described in a CDFW report from 1938 as “some of the best spawning areas in the entire watershed.” Recent studies suggest that this still holds true.
Additionally, much of the headwaters are protected from future development. Almost all of the watershed above Scott Dam is located in Mendocino National Forest, with a portion of the area in the Snow Mountain Wilderness.
Without access to these upstream areas, salmon are confined to lower river sections that increasingly face warming temperatures, invasive species, and other stressors driven by climate change. By reconnecting the river’s full migratory corridor, dam removal will support salmonids’ life-cycle needs, boost population resilience, and enhance overall river health.
While CalTrout strongly supports dam removal, we are also committed to restoration of the entire Eel River watershed. Our Eel River Watershed Restoration and Conservation Program embraces a holistic, community-driven approach to restore the watershed. This intensive planning and prioritization effort will help those working on restoration in the Eel River be efficient with limited funding and identify the highest priority restoration actions. This effort is ongoing, with phase 2 of the initiative starting now, supported by funding from the California Department of Fish and Wildlife (CDFW).
5. Dam removal could help reduce the number of invasive pikeminnow
Non-native Sacramento pikeminnow were introduced into Lake Pillsbury in the late 1970s and have spread throughout the Eel River. Although pikeminnow are native to California and the nearby Russian River, they are not native to the Eel River. Over the past 50 years, they have become a major obstacle to salmonid recovery. Once pikeminnow reach a certain size, they become aggressive predators capable of consuming a wide range of prey, including salmon and steelhead.
Beyond direct predation, pikeminnow also compete with salmon and steelhead for food and habitat. They feed on many of the same insects that juvenile salmonids rely on, and their presence can alter the behavior and distribution of young fish. Pikeminnow prefer slower-moving, warmer waters than salmonids; as a result, the Potter Valley Project reservoirs have large populations of pikeminnow.
The Wiyot Tribe has led pikeminnow monitoring and suppression efforts in the Eel River for years. CalTrout, UC Berkeley, CDFW, and Stillwater Sciences have collaborated with the Tribe to understand how pikeminnow suppression supports salmon recovery. In addition to direct suppression efforts, CalTrout scientists have been studying pikeminnow behavior and biology in the Eel River. Studies on the South Fork Eel River suggest that a significant percentage of pikeminnow migrate throughout the system at different times of the year. These fish seem to move downstream during winter, favoring the deeper, slower pools in the mainstem. In the summer, they migrate back upstream in search of food and possibly to spawn. While more research is needed, this indicates that the reservoirs may help pikeminnow maintain a foothold in the upper portion of the watershed, where they might otherwise move downstream. Dam removal will not only allow salmon access to smaller tributary streams where young fish can safely start their lives, but it will also reduce the amount of warm and slow water created by the reservoirs, which will reduce the amount of habitat that favors pikeminnow over salmon.
6. The Eel River will be California’s longest free-flowing river
At nearly 200 miles long and with a watershed of more than 3,500 square miles, the Eel is set to become the longest free-flowing river in California after the dams are removed, eclipsing the Smith River in the far northern corner of the state.
What about the Klamath? While the Klamath has been a hopeful story, two dams upstream still alter river flows and fish passage, though arguably to a lesser extent than the four dams just removed. Just days after the removal of Iron Gate Dam on the Klamath River, monitoring teams documented the first Chinook salmon passing above the former dam site. In the months following, thousands of fish passed the site, demonstrating what salmon biologists have long understood: these fish are well adapted to take advantage of new habitats once they are unlocked.
California’s North Coast is well-positioned for salmon recovery, as multiple rivers in the region are showing promising population trends. A collection of rivers with well-established salmon runs helps buffer populations from individual events that could otherwise jeopardize smaller populations. Revitalizing salmon populations will bring significant economic, cultural, and ecological benefits to the area, and the restoration of the Eel River will play a crucial role in the widespread recovery of salmon across the region.
The post Six Things to Know about the Potter Valley Project and Eel River Restoration appeared first on California Trout.
