Restricted fish passage at dams is being used to help limit the spread of invasive fish species in the US. Research undertaken by the US Fish and Wildlife Service, US Geological Survey, and Department of Natural Resources has investigated how dams in the Upper Mississippi River (UMR) not only affect the large-scale migration of native fish, but those of invasive species too.
Increasing the understanding of how fish move through lock and dam structures is critical for developing deterrent strategies that effectively limit the spread of aquatic invasive species while protecting migration corridors for native fish.
A series of 29 navigation locks and dams across the UMR basin has led to a high degree of channel fragmentation that impacts fish migration, with fish passage through dams being influenced by the design features of individual structures. To give greater insight into this, a two-year study tracked the native American paddlefish and invasive bigheaded carp across more than 600 river kilometres and 16 navigation locks and dams (LD) of the UMR. As a variety of socioecological problems are associated with increasing invasive bigheaded carp populations, such as safety hazards for boaters to food web disruptions, it is considered necessary to prevent further upstream spread.
As detailed in the research, LD 19 has a hydroelectric facility and the highest vertical lift of the active navigation locks on the UMR. It also has a hydraulic head that is too great to permit fish passage through the gated portion of the dam. And with LD 15 and LD 14 infrequently in open-river conditions, such restrictions on upstream passage at LD 19 and LD 15 have played a large role in reducing the population of invasive carp upstream, and is why the portion of the UMR between LD 19 and 15 is seen as a focal point for invasive carp control.
In their research published in Scientific Reports, Fritts et al say that in order to effectively balance the trade-offs between reducing invasive carp passage and facilitating the passage of native species, information is needed on how fish passage is affected by dam operations and other influential factors, such as temperature. Indeed climate change is likely to have more of an influence on fish movement, and may result in such changes to the timing of seasonal food pulses.
The purpose of this study was to examine movements of paddlefish and bigheaded carp with respect to dams and the abiotic factors affecting both dam operations and fish physiology. The researchers used consecutive years with contrasting conditions to explore how fish responses changed as conditions varied between 2022, a low-water year, and 2023, and a high-water year.
As the authors explained, large-scale comparison of native and invasive fish passage is an important step to facilitate a stronger understanding of how climatic variables such as precipitation and warming temperatures affect the abilities of native and invasive species to traverse the existing infrastructure of the UMR.
The results highlighted that dam operations during controlled hydrologic conditions can limit upstream passage. Conversely, during uncontrolled hydrologic conditions, when the dams allowed for open-river conditions, fish moved rapidly upstream. Characterising the magnitude and relative duration of periods when upstream migrations are inhibited by dams is important for both the conservation of native fishes and control of harmful invasive species. Likewise, understanding fish behaviour during brief windows of unregulated hydrological conditions, when dam gates are raised from the water, is also important for natural resource managers to consider when developing fisheries management plans.
Efforts to develop and deploy deterrent technologies designed to limit the movement of bigheaded carp and disconnect their populations should also balance the needs of native species that benefit from these intermittent pathways created by dam operations. The authors acknowledge that these concerns represent a difficult trade-of for river managers tasked with protecting important native species and controlling the spread of harmful non-native species.
Salmon restoration
Efforts to reintroduce salmon into historical habitat blocked by dams has been undertaken by Kleinschmidt Associates in partnership with Anchor QEA in the US. Together they have launched a landmark project for the Upper Columbia United Tribes (UCUT) to lead the development of fish passage systems at Chief Joseph and Grand Coulee dams. These dams represent two of the largest hydropower production facilities in the US and are the last in the Columbia River Hydropower System without fish passage capabilities.
The project marks a significant milestone in UCUT’s efforts to reintroduce salmon to the Upper Columbia River. It will focus on feasibility studies, planning oversight, and engineering design services to develop the fish passage systems. Kleinschmidt and Anchor QEA will collaborate with UCUT and its member tribes (specifically the Coeur d’Alene, Colville, and Spokane tribes), dam owners, and key regulators to advance the UCUT’s Phase 2 Implementation Plan, which aims to balance ecological, cultural, and hydropower priorities in restoring salmon to their ancestral habitats.
“As we begin the critical step in our 20-year journey to reintroduce salmon into the Upper Columbia, we are grateful to welcome the expertise of Kleinschmidt and Anchor QEA teams in advancing fish passage solutions. With this partnership, we move closer to restoring a resource vital to the cultural and ecological heritage of the people of the upper Columbia”, says Laura Robinson, Policy Analyst, Upper Columbia United Tribes. “Together, we will ensure that future generations can once again rely on the resilience and abundance of these waters.”
“We are excited and honoured to be a part of such an important project, working in partnership with many stakeholders to develop solutions to fish passage problems which the dams have contributed to since their inception,” says Andy Holmes, Project Manager at Kleinschmidt. “The fish in this region have an ancestral and spiritual connection to the people who live here, dating back thousands of years. It is a privilege to work together towards restoration.”
Kleinschmidt’s partnership with Anchor QEA brings together expertise in engineering, biology, stakeholder facilitation, and permitting to lead this high-impact project. The combined team will coordinate with the US Bureau of Reclamation, the US Army Corps of Engineers, Bonneville Power Administration, NOAA Fisheries, the US Fish and Wildlife Service, Washington Department of Fish and Wildlife, Avista Utilities, as well as the Indigenous communities.
The project is described as being a remarkable step towards salmon restoration and honouring the cultural and ecological legacy of the Upper Columbia United Tribes. Such a transformative effort is blending science and collaboration to address generations of ecological disruption, and holds profound significance for Indigenous communities and the environment.
The project’s timeline is driven by the natural lifecycle of the region’s salmon. Interim adult fish passage facilities are expected to be operational at Chief Joseph Dam by 1 July 2028, and juvenile facilities at Grand Coulee Dam by 31 March 2030.
Survival studies
From 2008 to 2018, acoustic telemetry studies evaluated dam passage survival of spring migrant Chinook salmon and steelhead smolts at seven of the eight federally operated dams on the lower Snake and Columbia rivers in the US. Data from over 87,000 dam passage events were evaluated to identify the effect of spill operations, environmental conditions, and fish characteristics on powerhouse passage probability.
In general, powerhouse passage was positively correlated with discharge, negatively correlated with forebay temperature and fish size, and higher for fish that passed the dam at night and for those that approached from the powerhouse side of the river, suggesting powerhouse passage is largely a function of smolt activity level and swimming ability.
As this research by the Pacific Northwest National Laboratory and the University of Washington showed, spilling large volumes of water to reduce powerhouse passage is likely to be most effective during times of reduced activity and swimming ability (eg at night, high flows, and cold temperatures). The authors say this information can be used to develop dam- and time-specific spill operations that optimise smolt passage, power generation, and other competing demands, such as adult passage.
Strategic restoration
A strategic restoration development paradigm to break, what they call, unfavourable lock-ins from past hydropower development, has been proposed in research undertaken by Valerio Barbarossa and Rafael Schmitt, and published in One Earth.
Looking at Asia’s Lower Mekong River, strategic multi-objective optimisation and habitat fragmentation modelling for 710 fish species has been used to design restoration development policies which, according to the authors, highlight the essential role of restoration in combination with strategic planning for future sustainable hydropower worldwide.
“Our results show that a combination of removing high impact dams, fishways retrofitting, and strategic planning can break locked-in environmental impacts and restore connectivity to a level achievable had strategic planning been adopted before the onset of hydropower deployment,” Barbarossa and Schmitt say.
They believe their results for the Mekong make a point for integrating dam scale mitigation and strategic planning into restoration development policies. They go on to discuss that the current dam portfolio in the Mekong is “a result of non-strategic hydropower development in the past two decades”. It has also locked in avoidable trade-offs between hydropower and fish and has impacted the livelihoods of people depending on the world’s most productive freshwater fisheries.
Even if strategic planning is adopted in the future, the authors claim there remains only a limited potential to strike better trade-offs between conflicting objectives. With strategic dam removal, they believe future hydropower portfolios could achieve trade-offs similar to what could have been achieved when adopting strategic approaches from the onset of hydropower development. Although such restoration development strategies will be challenging to implement, they “would be critical to leverage hydropower’s benefits for climate mitigation with the fewest impacts on biodiversity and associated livelihoods”. In addition, exploring the benefits of restoration development also calls for significant efforts to close data and knowledge gaps.
Quantitative assessments
Quantitative assessments have also been carried out into the cost of using positive barrier screens to prevent fish entrainment at hydropower facilities. Matson et al, in their study published in The Journal of Environmental Management, say such information is of value to the hydropower community because it helps provide a comparison into the cost effectiveness of alternative strategies for protecting aquatic resources.
The analyses showed that for fish exclusion screens, capital costs per unit flow were greater for powerhouses with higher theoretical head heights (ie power governed predominately by higher-head, lower flow projects). Such higher costs could be driven by increased costs associated with materials, requirements for larger quantities of material (eg larger screens), difficulty of construction, or a combination of some or all of the above.
A case study comparison with an ongoing low-head project by Natel Energy on the James River near Richmond in Virginia, estimated a ten-fold difference in the capital cost of exclusion if construction requires an entire stand-alone concrete structure, as opposed to replacing existing trash rack panels with 0.75-in wedge wire screen. Further exploration would benefit greatly from the inclusion of additional data.
Matson et al conclude that their data on the costs of fish exclusion screening was in general agreement with previously published qualitative information. They found that complete exclusion of fish can require high capital costs. In addition to excluding fish from turbine entrainment, the authors say capital costs may be required for the planning, construction, and evaluation of infrastructure to provide safe passage of fish across a dam, depending on stakeholder objectives and the scale of the project.
References
Flooding and dam operations facilitate rapid upstream migrations of native and invasive fish species on a regulated large river by Mark Fritts, Daniel Gibson‑Reinemer, Douglas Appel, Katharine Lieder, Cody Henderson, Amanda Milde, Marybeth Brey, James Lamer, Dominique Turney, Zachary Witzel, Emily Szott, Grace Loppnow, Joel Stiras, Kayla Zankle, Devon Oliver, R. John Hoxmeier & Andrea Fritts . Scientific Reports | (2024) 14:20609 https://doi.org/10.1038/s41598-024-70076-4
Factors affecting powerhouse passage of spring migrant smolts at federally operated hydroelectric dams of the Snake and Columbia rivers Ryan A. Harnish, Kenneth D. Ham, John R. Skalski , Richard L. Townsend, and Rebecca A. Buchanan. Can. J. Fish. Aquat. Sci. 80: 1949–1966 (2023) https://cdnsciencepub.com/doi/10.1139/cjfas-2022-0217
Strategic restoration-development mitigates trade-offs between hydropower and fish habitat fragmentation in the Mekong by Valerio Barbarossa and Rafael J.P. Schmitt. One Earth 7, 1096–1107, June 21, 2024. Elsevier. https://doi.org/10.1016/j.oneear.2024.05.009
Estimated capital costs of fish exclusion technologies for hydropower facilities by Paul G. Matson, Kevin M. Stewart, Gbadebo A. Oladosu, Emrat Nur Marzan, Scott T. DeNeale. Journal of Environmental Management, Volume 351, 2024, 119800, ISSN 0301-479. https://doi.org/10.1016/j.jenvman.2023.119800.
