Hydropower plays an essential role in supporting the reliability of America's electrical grid. Not only is hydropower widely available and relatively inexpensive, but it's also one of few renewable resources that can be used to provide energy storage and rapid-response electricity generation during periods of fluctuating energy demands, providing critical services that support bringing more solar and wind energy online. In the years to come, this versatility and reliability will only grow in importance, as will the need to ensure sustainable operations at hydropower facilities.
As part of America's clean energy transition, the hydropower sector has a duty to balance high-performing engineering with environmental protections that ensure the long-term sustainability of natural resources and ecosystems. Dams, diversions, and culverts (or drainage structures that move water under roads, railways, and other infrastructure) can restrict fish migration and access to habitats needed to complete their life cycles. With that in mind, the U.S. Department of Energy including the Water Power Technologies Office (WPTO), other federal agencies, and academic and industry partners have made significant investments in research, development, and testing of numerous fish passage technologies to help fish and other aquatic species navigate hydropower facilities safely while reducing environmental impact.
Rivers and freshwater species are highly impacted worldwide by combined threats of invasive species, competing water uses, pollution, power production facilities, overfishing, and more, causing steep drops in many fish populations and the biodiversity of rivers. Fish passage technologies are one part of the restoration solution to ensure populations of fish and other aquatic species are able to thrive and provide their economic, ecological, and culturally important benefits to local communities while still maintaining critical energy infrastructure across the United States. In areas with declining fish populations, investments in fish passage support restoration and recovery efforts by enabling fish access to important habitats.
Hydropower facilities currently provide 28.7% of all U.S. renewable energy and 6.2% of total U.S. electricity generation, but both the facilities and the environments they operate in are extremely diverse. As a result, there's no one-size-fits-all approach to fish passage.
Here are some of the conventional ways hydropower facilities support fish passage:
Fish Ladders
Fish ladders have been used since the 1800s to help provide a route for fish moving upstream. Fish are directed by flows of water, feature barriers, or nets into the fish ladder. From there, ladders contain a series of increasingly elevated "steps," or pools filled with water, that fish are able to swim and leap up until they've moved past the facility. Fish ladders have seen multiple designs over the years, depending on the size of the hydropower facility, the river flow, the species of the fish affected, and the technology available at the time, but all are designed to help fish pass through dams and other structures and mitigate river connectivity issues.
Trap and Haul
It may be impractical to install a full fish ladder at certain dams. Instead, a trap-and-haul system can be used to help move fish upstream. Fish are directed to a location where they are trapped or gathered in pools or tanks and then transferred into specialized tankers or barges. The ships then release the fish into the river on the other side of the dam. Every trap-and-haul design is different depending on the facility.
Fish Lifts
Fish lifts are designed for fish to swim into a hopper or chamber that functions like an elevator. After a certain period of time or number of fish, the lift moves the fish like an elevator and releases them so they can continue on their way. Fish lifts tend to work well for large numbers of fish and multiple species of fish, including those that may be weaker swimmers.
Here are some of the innovative fish passage and monitoring technologies companies have advanced with support from WPTO:
Advanced Turbines for Downstream Fish Passage
To reduce the impacts to fish that are unable to be guided away from turbine intakes, significant investments have been made to enable the design of specialized turbines that reduce the risk of injury and harm to fish. One example of this approach is Natel Energy's Restoration Hydro Turbine (RHT), a unique turbine design with thicker blades, rounded leading edges, and a forward slant to the blade that allows for fish to safely move through hydropower facilities. In a field study conducted in coordination with Pacific Northwest National Laboratory
, the RHT allows for 99% of rainbow trout and American eel (two species that have been heavily impacted by hydropower dams) ranging from 8-20 inches in length to move through the turbine unharmed. The turbine can fit into multiple sizes and configurations of existing hydropower facilities, making the RHT safe and effective for fish of multiple size.
Another example is from the U.S. Army Corps of Engineers, which installed another type of turbine at the Ice Harbor Dam on Snake River in 2016. Since then, fish passing through those turbines have had a survival rate of 98%, compared to approximately 90% with previous turbine designs. Another example, the Alden Fish-Friendly Turbine, has seen similar results in lab-scale tests.
Innovative Designs for Fish Passage in Development
In fall 2023, WPTO announced six research and development projects focused on fish passage and protection will receive a total of $6.3 million in funding. These projects advance a variety of technologies, including a fish entry and transport system, an automated tool to track and classify fish moving through fish ladders, two evaluations of the RHT on different fish species, a new fish passage technology that could support multiple species, and a fish ladder designed specifically for East Coast species.
Tagging and Tracking
In addition to funding the development of advanced fish passage and turbine technologies, WPTO's Hydropower Program supports several efforts to better understand fish movement and monitor and validate fish passage technology. Understanding fish behavior around dams and other structures can improve species survival and fish passage technology in the future.
To do this, researchers tag fish with specialized sensors to track and monitor what species, size, and number of fish are passing through hydropower facilities, if they're injured, and how they respond to changes in water pressure, temperature, and other environmental conditions. Pacific Northwest National Laboratory is currently developing a new type of sensor small enough to study the behavior and survival of species such as American Shad. This migratory fish, which has immense economic and cultural value, has long suffered from declining populations along the natural range of their habitat. Safely tracking species like Shad that have never been studied at this level of detail will greatly enhance knowledge of fish behavior, habitat use, fishway use and performance, and fish survival rates at hydropower facilities.
Environmental DNA
One of the most promising, noninvasive methods for monitoring fish is environmental DNA and RNA. This approach involves collecting and analyzing RNA and DNA (genetic material present in all living organisms, some of which is released into the environment) from water samples in fish passage structures. Once the eDNA and eRNA is extracted, the genetic code is sequenced and compared to publicly available DNA and RNA sequences of known species to enable identification. By collecting this information, researchers are able to know which fish are swimming in the water and how they're responding after passing through or over the dam. Soon, researchers may also be able to know exactly how many fish are passing as well.
Hydropower plays an important role in the electrical grid and is likely to grow as more solar and wind resources come online. Ensuring environmental stewardship by lessening the impacts on fish and other aquatic species is an essential step in working to create a clean energy economy that helps fight the effects of climate change and maintains an economically competitive and reliable energy sector.
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