Science Response : risk to fish from VLH turbine installations

One of the most significant concerns with hydroelectric power production is injury and mortality of fish passing through turbines during intentional or unintentional downstream passage (Algera et al. 2020). There are several mechanisms by which fish can become injured or killed as a result of passage (entrainment) through turbines as summarized by Čada (2001), including rapid and extreme pressure changes, cavitation, sheer stress, collision, turbulence, and grinding. As a result, developers have been working for decades to create ‘fish friendly’ turbines that incorporate features to make them less hazardous to entrained fish (Fraser et al. 2007, Foust et al. 2011, Romero-Gomez et al. 2022, Watson et al. 2022). To determine whether a turbine is indeed ‘fish friendly’, not only does mortality rate need to be quantified, but sublethal effects must also be considered (Ferguson et al. 2006). Many current hydro entrainment mortality monitoring plans typically involve periodically walking downstream of the turbine to observe and record dead fish; this level of monitoring likely does not yield reliable information as to the risk to fish. Increasingly, other methods of monitoring entrainment mortality are being employed, including fish flushing trials and modelling to estimate the death of fish from entrainment, but to date there are no standard or consistent methods considered as ‘best practices’. Several novel turbine technologies (Quaranta et al. 2022) are being proposed at new and existing infrastructure (weirs, non-power dams), which still need to be assessed for their ‘fish friendliness’ (Cooke et al. 2011) and Canadian application (NRCan 2018). Low head (< 15 m) dams are being explored as viable hydropower options, which could add between 5-10 GW of power (Tung et al. 2007, or about 10% of Canada’s 82.3 GW of installed capacity, IHA 2022) to Canada’s total energy generation capacity. The Very Low Head (VLH) turbine, developed by MJ2 Technologies, is a unique, cost-effective class of turbines designed to address a head of 1.4-4.5 m, discharge of 10-30 m3/s and up to 500 kW of capacity (Fraser et al. 2007, Quaranta et al. 2022). The standard configuration consists of 8 Kaplan-style adjustable runner blades and 18 fixed guide veins, with a diameter of 0.6-5.6 m. The VLH turbine design incorporates several features designed to minimize impact to fish including: • using a large runner diameter (which allows for low velocity and negates the need for a draft tube), • minimizing velocity and pressure gradients, • minimizing the tip gap and the number of blades, and • ensuring the shape of the Kaplan style runner blades is blunt (Fraser et al. 2007). A VLH turbine that was installed in 2015 at Wasdell Falls on the Severn River, ON, provided a unique site for the first study of this new technology in Canada. The VLH installation on the Severn River was supported by NRCan as a demonstration site to represent a clean and reliable low-impact source of electricity. VLH technology allows for significant cost savings related to civil works due to its modularity concept, making the development of VLH hydro resources economically feasible, yet it is important that testing was conducted in Canada to determine if this technology can indeed be considered ‘fish friendly’ for Canadian taxa and systems. Using acoustic telemetry, live fish passage, and sensors designed to record the conditions experienced by fish as they pass through turbines, this research aimed to provide a direct quantification of the risk of entrainment, injury, and immediate or delayed mortality to fish resulting from the VLH turbine installation at Wasdell Falls. Since the Wadell Falls installation was at the site of an existing dam, this research was designed to specifically quantify the increased risk to fish from the installation of the turbine at an existing barrier, not to assess the full impacts of the presence of the dam itself. The risk of entrainment to resident fish upstream of the VLH was estimated by measuring the rate of entrainment of tagged fish via acoustic telemetry. Live fish, representative of the local fish community, were flushed through a VLH turbine to estimate expected injury and mortality rates for resident fish that pass through the VLH turbines. Together, the likelihood of entrainment and risk of injury or mortality from turbine passage can be used to provide an estimate of the overall risk to the fish upstream of the VLH. In addition to live fish passage, electronic sensors were passed through the VLH turbine to provide quantitative information on the physical conditions experienced by fish during passage, some of which may not have presented as obvious injuries during the live fish trials. The results presented in this Science Response Report are intended to provide direct quantification of risk from VLH turbines to Fisheries and Oceans Canada (DFO)’s Fish and Fish Habitat Protection Program (FFHPP). Specifically, the objectives are as follows: 1. To determine the overall risk to the resident fish community from the VLH turbine installation at Wasdell Falls; 2. To determine the level and type of monitoring required at future installations; and, 3. Identify uncertainties and knowledge gaps, and if necessary, recommend additional information, research, monitoring, data collection, etc. that is required to further assess the potential impacts of VLH turbine installations on Canadian fish communities. This Science Response Report results from the regional peer review of December 5-6, 2023, for the Risk to Fish from Very Low Head Turbine Installations.

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