The removal of Scott Dam and Cape Horn Dam could help boost populations of Chinook and steelhead by providing access to hundreds of miles of prime, cold-water spawning and rearing habitat, acutely needed because climate change can push water temperatures above what\u2019s tolerable for salmonids. The dams, known as the Potter Valley Project, belong to power company PG&E as part of a hydroelectric facility that also includes a transbasin diversion, which sends water through a 1-mile-long tunnel to the Russian River to irrigate fields in Potter Valley and provide water for downstream users in Sonoma County.<\/p>\n
The small, 9.4-megawatt hydroelectric project has been economically unprofitable for years, and after PG&E found no willing buyers, it declined to renew its operating license in 2019. An equipment failure in the summer of 2022 stopped power production. A draft plan for surrender and decommissioning is expected at the end of the year. But it doesn\u2019t guarantee either dam\u2019s removal.<\/p>\n
\u201cDecommissioning can just mean locking the gates and walking away,\u201d says Charlie Schneider, the Lost Coast project manager for\u00a0California Trout<\/a>. \u201cOr it can mean full dam-facility removals.\u201d<\/p>\n It can also include something in between, but Alicia Hamann, executive director of\u00a0Friends of the Eel River<\/a>, hopes the Federal Energy Regulatory Committee, which oversees regulation of hydroelectric dams, will require full removal of the project.<\/p>\n \u201cIt would be highly unusual for FERC to allow PG&E to lock it up and walk away,\u201d says Hamann. The project has risks not just to fish, but potential public safety hazards as well. Looming questions include whether all or some of the project would need to be removed and what would happen to the water diversion.<\/p>\n Data suggests that the Eel River once teemed with salmonids, with estimated annual runs of more than 1 million salmon and steelhead, including some 800,000 Chinook. Now those fish populations are between 1% and 3% of their historic numbers.<\/p>\n Experts attribute the declines to a combination of pressures, including dams, logging, grazing, and the introduction of the Sacramento pikeminnow, a salmon predator.<\/p>\n A\u00a0report<\/a>\u00a0from fisheries biologists at the U.C. Davis Center for\u00a0Watershed Sciences found \u201cthat coho salmon, Chinook salmon and steelhead are all on a trajectory towards extinction in the Eel River basin, with only winter steelhead being widely enough distributed and abundant enough to persist beyond the next 50 years.\u201d<\/p>\n What role dams have played isn\u2019t easy to calculate, but the 95-foot-tall Cape Horn Dam, constructed in 1908, has fish passage that experts consider outdated and inefficient.<\/p>\n \u201cWe know that the fish ladder isn\u2019t effective at passing fish,\u201d says Schneider, \u201cso almost certainly some of them are getting to that concrete wall in the river and turning around and maybe spawning in more marginal habitats.\u201d<\/p><\/blockquote>\n The fish ladder fails to operate when the river has high flows, and it can clog with debris, forcing it to be temporarily shut down.<\/p>\n \u201cThere\u2019s a structure at the base of the fish ladder called \u2018the hotel\u2019 where the fish enter and then get oriented and find the trigger flow to go the right direction up the fish ladder,\u201d says Hamann. \u201cAnd that entire structure can get completely inundated.\u201d<\/p><\/blockquote>\n There\u2019s also no protection from predators, \u201cwhich makes it like an all-you-can-eat buffet for otters,\u201d she says.<\/p>\n If fish do clear the ladder, they then hit the 141-foot-tall Scott Dam 12 miles upstream. This is the end of the line. Scott Dam, which was erected in 1922, contains no fish passage and blocks about 288 miles of high-quality spawning and rearing habitat. Headwaters of the Eel River. Photo: CalTrout\/Mike Wier<\/em><\/p>\n While that\u2019s only about 10% of the whole watershed, it\u2019s among the best areas for these fish.<\/p>\n \u201cBased on our thermal and geomorphic habitat assessments, the blocked Upper Mainstem generally contains a higher proportion of suitable habitat for all freshwater salmonid life stages than much of the rest of the Eel River Basin,\u201d<\/p><\/blockquote>\n found researchers from the National Marine Fisheries Service and other institutions in a\u00a0study<\/a>\u00a0published in the\u00a0Canadian Journal of Fisheries and Aquatic Science<\/em>\u00a0in 2021.<\/p>\n That\u2019s because of the gravelly sediment that\u2019s ideal for spawning, the availability of food, and the temperature of the water.<\/p>\n \u201cThe habitat in the upper mainstem Eel River watershed provides cold-water refugia in tributaries over summertime for steelhead trout as well as ample spawning grounds for Chinook salmon and steelhead trout,\u201d confirmed researchers of a\u00a0study<\/a>\u00a0published in\u00a0Northwest Science<\/em>\u00a0in 2020.<\/p><\/blockquote>\n The colder water also can help protect them from invasive pike minnows, who Schneider says are better adapted to warmer conditions.<\/p>\n The population declines have been a loss for recreational and commercial fishers, as well as Tribes.<\/p>\n \u201cWe\u2019re really in crisis mode,\u201d says Adam Canter, natural resources director of the\u00a0Wiyot Tribe<\/a>, whose ancestral lands encompass the lower Eel River watershed. \u201cThe Tribe has lost a cultural and subsistence icon by not being able to fish for Chinook, coho and steelhead as they used to.\u201d<\/p><\/blockquote>\n Lamprey, whose numbers have also declined significantly, are a species of special concern in California \u2014 and are especially important for the Wiyot Tribe.<\/p>\n \u201cPacific lamprey are a really culturally important food for the Tribe,\u201d<\/p><\/blockquote>\n says Canter. Settlers mistook the long, slender fish for eels and incorrectly gave the river its English name for them. Like Chinook and steelhead, lamprey historically used the habitat above Scott dam as well and would benefit from the increased habitat.<\/p>\n Declining fish numbers aren\u2019t the only problem.<\/p>\n Friends of the Eel River also worries about seismic concerns at Scott Dam, which sits along a fault capable of producing a magnitude 7 earthquake. When engineers built the dam in the 1920s, they realized that the bedrock they were attempting to secure to part of the southern abutment was in fact a boulder that\u2019s part of a very slow but active landslide.<\/p>\n \u201cSo they decided to just re-engineer the dam to go right in front of that giant moving boulder,\u201d says Hamann.<\/p>\n Recent moves from the PG&E show that it\u2019s aware of some seismic issues.<\/p>\n In spring the company usually closes spillway gates at the dam to increase the amount of water behind the dam during periods of high runoff. But this March\u00a0PG&E announced<\/a>\u00a0that it wouldn\u2019t close the gates.<\/p>\n \u201cKeeping the spillway gates open at Scott Dam from this point forward allows us to reduce potential risk around seismic performance,\u201d the company said in a press release. \u201cNew information and updated analyses suggest the level of risk around seismic performance at Scott Dam is greater than the previous evaluation.\u201d<\/p><\/blockquote>\n If the dams are removed, it remains unclear how authorities will resolve the issue of the transbasin water diversion.<\/p>\n As it is now, \u201cThe Russian River gets all the benefits from this project. The Eel gets all the impacts. How is that fair?\u201d says Schneider.<\/p>\nFish on the Brink<\/strong><\/h3>\n
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<\/p>\nShaky Ground<\/strong><\/h3>\n
Basin Water Issues<\/strong><\/h3>\n
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