Analysis into water move and fish passage by means of dams within the US suggests new choices for assembly power and environmental wants, writes Alexandra Freibott for the US Dept of Vitality and Pacific Northwest Laboratory.
Hydropower dams present dependable renewable power, however in addition they have a direct influence on the atmosphere, particularly fish. Adjusting the quantity of water spilling over a dam might help fish efficiently navigate dams. However spilling extra water means much less water is accessible to supply energy. Figuring out when and the way a lot water to spill to assist fish move safely by means of dams whereas assembly grid reliability wants are critically vital questions.
Analysis at Pacific Northwest Nationwide Laboratory (PNNL) highlights the complicated dynamics round spill and fish passage by means of dams, and finds that spill isn’t at all times the largest think about profitable fish passage.
“We discovered that fish exercise, swimming capacity, and time of day all play a job in fish passage, typically extra so than spill ranges alone,” defined PNNL Earth scientist Ryan Harnish. “Our knowledge present that when younger salmon and steelhead are much less energetic within the spring—like at night time or in cooler water temperatures—spilling extra water could make a giant distinction in serving to extra fish keep away from passing by means of the powerhouse. However beneath different circumstances, greater spill ranges have little impact.”
That is precious data for decision-makers who’re tasked with balancing water wants for environmental well being and power demand. Figuring out when excessive spill ranges greatest help fish passage—and once they don’t—offers choices for balancing the tradeoffs related to hydropower technology and environmental impacts.
Monitoring fish by means of a dam in 3D
Spilling water might help fish swim efficiently over a dam as a substitute of immediately by means of the powerhouse—the a part of the dam that features the turbine. However the timing and quantity of water spilled impacts each fish passage and energy technology. To take a more in-depth have a look at how spill stage impacts fish passage, researchers wanted detailed monitoring data displaying when and the way fish handed by means of a dam.
The usual monitoring methodology within the Columbia River Basin is to tag particular person fish with passive built-in transponder (PIT) tags above the dam, that are detected as fish move by means of a selected a part of the dam known as the juvenile bypass system. Whereas very dependable, this strategy doesn’t present details about the varied different routes fish can journey by means of a dam—data wanted to find out how spill stage impacts fish passage. To get this data, quite a few research have been carried out between 2008 and 2018 utilizing a distinct methodology: acoustic telemetry.
The PNNL group analyzed the ten years of acoustic telemetry knowledge, together with 3D data on fish conduct, from a number of dams alongside the Snake and Columbia rivers. This allowed them to establish the route fish took by means of the dam and the exact time of their dam passage. Mixed with details about fish conduct and survival together with dam operations, they evaluated what elements have been most probably to have an effect on fish passage by means of totally different routes and circumstances. They particularly checked out spring salmon and steelhead smolts—younger fish migrating towards the ocean—to see how spill ranges affected the variety of smolts passing immediately by means of the powerhouse. The variety of smolts passing by means of the powerhouse turned out to be associated to their exercise stage and swimming capacity, not simply spill.
“Excessive spill ranges which are supposed to scale back the variety of fish passing by means of the powerhouse within the spring are more likely to be best when fish are much less energetic or have decreased swimming capacity, reminiscent of at night time, throughout excessive river flows, or in cooler water temperatures,” defined Harnish. “Excessive spill ranges weren’t the one most vital think about smolt passage throughout the board.”
These findings level to the necessity for extra research like this that may present complete details about precisely when and the way fish move by means of dams. That data might help decision-makers decide methods to greatest help fish passage and meet power wants sooner or later.
In a press release offered to PNNL, the Bonneville Energy Administration (BPA)—which markets energy from 31 federal dams throughout the Pacific Northwest—mentioned, “This publication is one other piece to the puzzle of understanding fish passage by means of the federal hydrosystem. It ought to present the area’s scientists and managers with further data to contemplate when evaluating operations that meet the a number of functions of the Columbia River System.”
(Above) The a number of paths fish can take when passing by means of and round a dam. The powerhouse consists of the generators and the juvenile bypass system proven on this illustration (picture credit score: Stephanie King, Pacific Northwest Nationwide Laboratory). CLICK IMAGE TO ENLARGE.
Balancing wants
Hydropower generates over half of the electrical energy in Oregon and Washington and is a key a part of a dependable electrical grid. Fish passage is important to help regional fish populations, significantly salmon, which maintain vital environmental, financial, and cultural significance. Figuring out when and the way a lot to spill—or not—is paramount to balancing these wants.
For instance, when river water ranges are low, most spill ranges are comparatively excessive. This excessive spill stage interprets to a giant lower in energy technology—equal to powering half 1,000,000 fewer houses. This research predicts that beneath these river circumstances, most spill ranges would assist fish passage by means of the powerhouse at night time, however would make little distinction throughout the day when power demand is often greater. This detailed data affords important perception for decision-makers and dam operators in search of methods to fulfill each power and atmosphere priorities.
“Evaluating power and atmosphere tradeoffs is a problem that requires the perfect out there knowledge to tell choices,” mentioned Alison Colotelo, PNNL Hydropower Program Lead. “Higher understanding of what impacts fish passage by means of dams and the function of spill is important to supporting fish populations and energy technology.”
This analysis was funded by BPA, as a part of a cost-share settlement to develop upon analyses initially funded and initiated by the Division of Vitality’s Water Energy Applied sciences Workplace.
