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North American diadromous fishes: Drivers of decline and potential for recovery in the Anthropocene

American Association for the Advancement of Science (AAAS) | January 28th, 2022

Summary

Diadromous fishes migrate between freshwater and marine habitats to complete their life cycle, a complexity that makes them vulnerable to the adverse effects of current

Diadromous fishes migrate between freshwater and marine habitats to complete their life cycle, a complexity that makes them vulnerable to the adverse effects of current and past human activities on land and in the oceans. Many North American species are critically endangered, and entire populations have been lost. Major factors driving declines include overfishing, pollution, water withdrawals, aquaculture, non-native species, habitat degradation, over-zealous application of hatcheries designed to mitigate effects of other factors, and effects of climate change. Perhaps, the most broadly tractable and effective factors affecting diadromous fishes are removals of the dams that prevent or hinder their migrations, alter their environment, and often favor non-native biotic communities. Future survival of many diadromous fish populations may depend on this.

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Optimizing the dammed: Water supply losses and fish habitat gains from dam removal in California

Journal of Environmental Management (Elsevier) | April 1st, 2014

Summary

Dams provide water supply, flood protection, and hydropower generation benefits, but also harm native species by altering the natural flow regime and degrading aquatic an

Dams provide water supply, flood protection, and hydropower generation benefits, but also harm native species by altering the natural flow regime and degrading aquatic and riparian habitat. Restoring some rivers reaches to free-flowing conditions may restore substantial environmental benefits, but at some economic cost. This study uses a systems analysis approach to preliminarily evaluate removing rim dams in California's Central Valley to highlight promising habitat and unpromising economic use tradeoffs for water supply and hydropower. CALVIN, an economic-engineering optimization model, is used to evaluate water storage and scarcity from removing dams. A warm and dry climate model for a 30-year period centered at 2085, and a population growth scenario for year 2050 water demands represent future conditions. Tradeoffs between hydropower generation and water scarcity to urban, agricultural, and instream flow requirements were compared with additional river kilometers of habitat accessible to anadromous fish species following dam removal. Results show that existing infrastructure is most beneficial if operated as a system (ignoring many current institutional constraints). Removing all rim dams is not beneficial for California, but a subset of existing dams are potentially promising candidates for removal from an optimized water supply and free-flowing river perspective. Removing individual dams decreases statewide delivered water by 0–2282 million cubic meters and provides access to 0 to 3200 km of salmonid habitat upstream of dams. The method described here can help prioritize dam removal, although more detailed, project-specific studies also are needed. Similarly, improving environmental protection can come at substantially lower economic cost, when evaluated and operated as a system.

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Pacific Salmon and Steelhead Trout: Managing Under the Endangered Species Act

Congressional Research Service (CRS) | November 30th, 2012

Summary

Along the Pacific Coast, 28 distinct population segments of Pacific salmon and steelhead trout are listed as either endangered or threatened under the Endangered Species

Along the Pacific Coast, 28 distinct population segments of Pacific salmon and steelhead trout are listed as either endangered or threatened under the Endangered Species Act (ESA), with three additional populations identified as “species of concern.” While no species of anadromous trout or salmon is in danger of near-term extinction, individual population segments within these species have declined substantially or have even been extirpated. The American Fisheries Society considers at least 214 Pacific Coast anadromous fish populations to be “at risk,” while at least 106 other historically abundant populations have already become extinct. Human activities—logging, grazing, mining, agriculture, urban development, and consumptive water use—can degrade aquatic habitat. Silt can cover streambed gravel, smothering fish eggs. Poorly constructed roads often increase siltation in streams where adult salmon spawn and young salmon rear. Removal of stream-side trees and shade frequently leads to higher water temperatures. Grazing cattle remove stream-side vegetation and exacerbate stream bank erosion. Urbanization typically brings stream channelization and filled wetlands, altering food supplies and nursery habitat. Habitat alterations can lead to increased salmonid predation by marine mammals, birds, and other fish. Dams for hydropower, flood control, and irrigation substantially alter aquatic habitat and can have significant impacts on anadromous fish. In addition, natural phenomena stress fish populations and contribute to their variable abundance. Current management efforts aim to restore the abundance of ESA-listed native northeast Pacific salmonids to historic, sustainable population levels. The National Marine Fisheries Service (NMFS, also popularly referred to as “NOAA Fisheries”) in the Department of Commerce implements the ESA for anadromous salmonids. When a federal activity may harm an ESA-listed salmonid, the ESA requires the federal agency to consult with NMFS to determine whether the activity is likely to jeopardize the survival and recovery of the species or adversely modify its critical habitat. Prior to the listing of salmonid “evolutionarily significant units” (ESUs) under the ESA, the Northwest Power and Conservation Council took the lead in the Columbia River Basin under the 1980 Pacific Northwest Electric Power Planning and Conservation Act, by attempting to protect salmon and their habitat while also providing inexpensive electric power to the region. Under this effort, federal agencies and public utilities have spent hundreds of millions of dollars on technical improvements for dams, habitat enhancement, and water purchases to improve salmon survival. Recent years have seen an increased interest by state governments and tribal councils in developing comprehensive salmon management efforts. This report summarizes the reasons for ESA listings and outlines efforts to protect ESA-listed species.

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Patterns, drivers, and a predictive model of dam removal cost in the United States

Frontiers in Ecology and Evolution (Frontiers) | July 24th, 2023

Summary

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Solar-power replacement as a solution for hydropower foregone in US dam removals

Nature Portfolio (Springer Nature) | August 26th, 2019

Summary

There is a growing dam removal movement in the United States, driven in part by environmental, safety and cost considerations. These include electricity-producing hydro-d

There is a growing dam removal movement in the United States, driven in part by environmental, safety and cost considerations. These include electricity-producing hydro-dams, many of which are ageing and will require substantial maintenance or removal over the coming decades. However, hydropower has been and remains an important source of energy for the development of the United States, presently generating about 6% of the nation’s electricity while providing essential grid services. As a potential solution to the conflict between these imperatives, industrial-scale photovoltaics (PVs) could be used for replacement of the energy foregone from hydro-dam removals either by installing the PV infrastructure in the area formerly inundated by the dam reservoir or through offsite replacement. Presently, the total PV generation in the conterminous United States is 35,919 GWh yr−1, or approximately 13% of hydropower generation. On the basis of actual hydropower generation in the conterminous United States in 2016 (that is, 274,868 GWh yr−1), we estimated that 529,885 ha of PVs would be needed to replace the generation of all 2,603 hydro-dams—an area approximately equal to the land size of Delaware. PVs could replace the total annual energy produced from these dams while requiring only 13% of their existing reservoir area. If all the hydro-dams in the United States were removed and only 50% of the emergent land was used for PVs, 945,062 GWh yr−1 power could be generated, which is 3.44 times the current hydropower generation. These analyses are theoretical and do not consider costs, which would be highly site specific. Replacement by PVs without energy storage could not replicate the dispatchability and grid services provisions of existing hydropower facilities; however, improving battery storage capabilities may ameliorate this shortcoming. We suggest that PVs could replace much of the annual electricity output of hydro-dams in the United States while using substantially less land area and providing considerable environmental and ecological benefits.

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Status and trends of dam removal research in the United States

Wires Water (Wiley) | September 6th, 2016

Summary

Aging infrastructure coupled with growing interest in river restoration has driven a dramatic increase in the practice of dam removal. With this increase, there has been

Aging infrastructure coupled with growing interest in river restoration has driven a dramatic increase in the practice of dam removal. With this increase, there has been a proliferation of studies that assess the physical and ecological responses of rivers to these removals. As more dams are considered for removal, scientific information from these dam‐removal studies will increasingly be called upon to inform decisions about whether, and how best, to bring down dams. This raises a critical question: what is the current state of dam‐removal science in the United States? To explore the status, trends, and characteristics of dam‐removal research in the U.S., we searched the scientific literature and extracted basic information from studies on dam removal. Our literature review illustrates that although over 1200 dams have been removed in the U.S., fewer than 10% have been scientifically evaluated, and most of these studies were short in duration (<4 years) and had limited (1–2 years) or no pre‐removal monitoring. The majority of studies focused on hydrologic and geomorphic responses to removal rather than biological and water‐quality responses, and few studies were published on linkages between physical and ecological components. Our review illustrates the need for long‐term, multidisciplinary case studies, with robust study designs, in order to anticipate the effects of dam removal and inform future decision making

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The Klamath River’s dams are being removed. Inside the effort to restore a scarred watershed

Los Angeles Times | March 24th, 2024

Summary

HORNBROOK, Calif. — Near the California-Oregon border, reservoirs that once submerged valleys have been drained, revealing a stark landscape that had been underwater f

HORNBROOK, Calif. — Near the California-Oregon border, reservoirs that once submerged valleys have been drained, revealing a stark landscape that had been underwater for generations. A thick layer of muddy sediment covers the sloping ground, where workers have been scattering seeds and leaving meandering trails of footprints. In the cracked mud, seeds are sprouting and tiny green shoots are appearing. With water passing freely through tunnels in three dams, the Klamath River has returned to its ancient channel and is flowing unhindered for the first time in more than a century through miles of waterlogged lands.

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