From the beginning, collecting information about how real fish interact with Restoration Hydro Turbines has been an integral part of our design process. We’ve performed controlled laboratory and field studies with biologists and engineering partners from Alden Research Laboratory, Pacific Northwest National Laboratory, and Kleinschmidt Associates to understand the effects of the RHT on migratory fish species across a range of operating conditions.
Hydropower operations have had major detrimental effects on fish populations, both migratory and resident. This article focuses primarily on the downstream passage of fish through turbines, although there are many other related issues concerning the safe, timely, and effective passage of fish through hydropower facilities, as well as habitat change and flow alterations associated with hydropower operations. The design of fish-safe turbines has significant value, as such machines could lock-in substantial environmental sustainability improvements at hydropower facilities while also allowing for simple and familiar hydropower plant design and operations.
Schneider, A., Watson, S. (2023). Design and validation of fish-safe hydro turbines for retrofit and new-build applications. This paper was published in The International Journal on Hydropower & Dams, Issue 5 and was presented at the HYDRO 2023 conference in Edinburgh (October 2023).
The objective of this study was to observe the effects of downstream passage through a novel turbine designed for fish safety, the Restoration Hydro Turbine (RHT), on American Eels Anguilla rostrata in a recirculating turbine test facility. A 55-cm-diameter RHT was operated under 10 m of hydraulic head and 667 revolutions/min. In total, 131 eels were passed through the turbine and 43 eels were used as experimental controls (length = 33.9–65.5 cm). High-speed video of passage through the runner region was captured for 89% of turbine-passed eels, and injury and behavioral effects were recorded immediately before and after passage, as well as after a 48-h holding period. A subset of 37 eels was additionally examined with X-ray imaging for internal injuries. The 48-h survival rate for both treatment and control groups was 100%, with no major internal or external injuries present after the holding period. This is a substantial improvement over eel survival rates through conventional Kaplan and Francis turbines, which may range from 40% to 95%, and suggests that hydropower turbines designed for safe downstream fish passage could be implemented without major impacts to eels. Mature American Eels migrate down rivers to spawn in the ocean, and may pass hydropower dams where the risk of entrainment in turbine intakes is high. In this study, eels were passed through a novel propeller-style turbine with a survival rate of 100%, a substantial improvement over conventional turbines.
Watson, S., Schneider, A., Santen, L., Deters, K. A., Mueller, R., Pflugrath, B., Stephenson, J., & Deng, Z. D. (2022). Safe passage of American eels through a novel hydropower turbine. Transactions of the American Fisheries Society, 151, 711–1. https://doi.org/10.1002/tafs.10385
Hydropower is a valuable renewable energy source, but its effects on the downstream passage of many riverine fish species are not well understood. Turbines that are designed to function as safe downstream passage routes for fish are being developed with the goal of mitigating the effects of hydropower operations on the environment. In this paper, we present the results of a study conducted with the juvenile life stage of the Alewife Alosa pseudoharengus, a major migratory species on the Atlantic coast of North America. The test was conducted at a small hydropower plant located in Freedom, Maine, with a single Restoration Hydro Turbine (RHT) operating under 7.5 m of gross head. Groups of 140–170 fish were released into the intake of a 55-cm-diameter RHT and were recaptured with a specialized trap at the turbine discharge outlet. The combined immediate and 48-h survival rates (±95% CI) for all treatments, corrected for control mortality, were 98.2 ± 2.0% and 100.0 ± 6.6%, respectively. The passage of Alewives through the runner region of the turbine was also captured with high-speed video. The results of the study demonstrate that the RHT, which is designed for fish safety, is an effective way to pass juvenile alosines downstream at hydropower facilities.
Watson, S.M., Schneider, A.D., Gardner, L.C., Apell, B.R., Thompson, P.C., Cadman, G.B., Gagnon, I.F., Frese, C.R. and Wechsler, J.F. (2023), Juvenile Alewife Passage through a Compact Hydropower Turbine Designed for Fish Safety. North Am J Fish Manage, 43: 465-475. https://doi.org/10.1002/nafm.10866
Compact turbines offer potential to reduce hydropower plant construction costs, but conventional turbine blade designs endanger entrained fish due to high blade strike speeds and thin leading edges. We evaluated the potential for combined blade leading edge slant and large leading edge thickness to increase strike survival. Rainbow trout (Oncorhynchus mykiss) were subjected to strikes with 100 mm thick blade analogues. At 10 m/s, strikes at fish length to blade leading edge thickness ratio (L/t) of 2 resulted in 98% survival at a location along the blade witha 30° slant relative to the tangential direction, compared to 26.8% survival at a location with 90°slant. For L/t 1.14-2, survival was found to be sensitive to location of strike within the mid-body region, determined from high-speed video. Strikes of 200 mm fish at 10 m/s resulted in 68% survival when body strike location was 0.58 (near caudal), and 7.9% when body strike location was 0.36 (near head). These results are consistent with previous trends and indicate opportunities to improve turbine blade design for greater entrained fish survival at higher turbine speeds, at both low head (<30 m) and high head projects.
Stephen V. Amaral, Sterling M. Watson, Abraham D. Schneider, Jenna Rackovan & Andrew Baumgartner (2020) Improving survival: injury and mortality of fish struck by blades with slanted, blunt leading edges, Journal of Ecohydraulics, 5:2, 175-183. 10.1080/24705357.2020.1768166
The potential of hydropower turbines to cause injury or mortality to fish is a concern. To reduce this risk, engineers have begun to develop a conically arranged, cantilevered electrified bar rack (Center Sender). This device is proposed to be mounted within the intake of a turbine, guiding downstream-passing fish towards the center of the turbine where blade velocities are lower and blades are thicker, likely reducing the potential for fish to be injured. A simplified version was installed in a flume for testing with Rainbow trout (Oncorhynchus mykiss) while examining several parameters such as electrification, bar spacing, bar angle, and water velocity. The most effective settings were observed to be a water velocity of 1.0 m s−1 with all bars installed at an angle of 40° with electrification on. Other combinations were still effective but had varying results. A minimal proportion (2.3%) of fish passed at lower velocities with bars electrified and mounted at 20°, suggesting that while it functions well as a guidance device in high-velocity conditions, it performs better as a barrier at lower velocities. The study suggests that the Center Sender has promising potential for reducing the harmful effects of hydropower turbines on fish populations by guiding them away from stressors. Further research is needed, but current results encourage its potential use in hydropower operations.
Pflugrath BD, Watson S, Haug J, Harnish R, Colotelo AHA, Schneider A. (2023). Examination of an Electrified Bar Rack Fish Guidance Device for Hydropower Turbines. Water, 15(15):2786. https://doi.org/10.3390/w15152786