Flow characteristics in tailrace: understanding how hydrodynamics may attract fish to hydropower plant in South America

Abstract

Hydropower plant (HPP) operation may influence downstream flow regimes, which can affect the fish movement. In South America, tailrace fisheries are often killed or injured when interacting with spillways and turbines. Hydrodynamic flow-pattern studies are essential to facilitate mitigation. We developed a computational fluid dynamics model to investigate flow downstream of Três Marias HPP (Brazil). Included in the model were the draft tubes, tailrace and a 3-km river reach. We simulated a common scenario consisting of three active turbines on the right side of the powerhouse (109.6, 108.0 and 108.0m3s–1) and three inactive turbines, by using Ansys Fluent (ver. 12). We identified a straight discharge plume from the right-most turbine that was constrained by the right-side wall. Further, there was the generation of significant plumes from Turbines 2 and 3. The maximum velocities in these plumes appears not to be a barrier for Pimelodus maculatus and Prochilodus costatus, because their prolonged swimming speeds for their maximum total length were higher than the modelled velocities. The results will support mitigation decisions such as fish passage and turbine-screen design in this particular HPP and may be a model for further studies in the South America.

Downstream alterations on hydrodynamic fields by hydropower plant operations: implications for upstream fish migration

“…4b) for a discharge of 462 m 3 /s. The dashed lines limit the maximum and minimum values found in the tailrace, excluding outliers indicated that the streamlines from turbine 1 and turbine 2 are faster than the streamlines from turbine 3, while a secondary flow pattern, which was created by turbine 1 streamlines, went in the direction of the left bank parallel to the long axis of the dam (Santos et al, 2018). Thus, variations in the flow patterns of turbine 1 can easily be detected by fish located near the left bank (analysis volumes 7 and 8).…”

“…The fish-kill events that occurred in areas of the tailrace and downstream of the spillway in 2007 motived the studies about the congregation of fish in those areas (Andrade et al, 2012;Loures & Pompeu, 2015). The occurrence of ''false attraction'' was suggested in another study (Suzuki et al, 2017) and the turbine plumes may have a wide effect on velocity field of tailrace for specific scenario of three operating units (Santos et al, 2018). Therefore, our objectives in this study were to: (1) alterations in flow downstream of a dam induced by HPP operation that might promote ''false attraction'' of these three neotropical fish species and (2) possible migration routes in the downstream river reach, for different ranges of discharge and combination of operating turbine, which will be obtained by comparison between hydrodynamics and fish swimming speeds.…”

“…The attraction of fish to the tailrace, especially for unsafe areas in the HPP (e.g., downstream areas of spillways and draft tubes) (Suzuki et al, 2017), is considered ''false attraction'' and may result in injury, increased exposure to predators, a higher risk of disease and stress, and mortality (Scruton et al, 2007). Studies on ''false attraction'' or failures in fishway attraction analyze the influence of hydrodynamic parameters on the behavior of upstream migrating fish (Johnson et al, 2007;Burnett et al, 2013;Gisen et al, 2017;Suzuki et al, 2017;Santos et al, 2018;Gutfreund et al, 2018;Makrakis et al, 2019). Most research focuses on salmonid species and rarely addresses hydraulic (e.g., water velocities, gradient velocities, depth turbulence, or even discharge) characteristics of tailraces or downstream areas may influence fish movement.…”

Hydropower development and fish management: a food–water–energy nexus requiring international and multidisciplinary approach

“…information on the efficiency of fish ladders, or fishways, at hydropower dams to improve passage of upstream-migrating fish (Amaral et al 2018a;Baumgartner and Wibowo 2018;Bido et al 2018;Dodd et al 2018;Fjeldstad et al 2018;Gutfreund et al 2018;Meulenbroek et al 2018); several key technologies to improve operation of bypass systems to ensure downstream-migrating fish avoid passage through turbines (Amaral et al 2018b;Fjeldstad et al 2018;Klopries et al 2018;Nyqvist et al 2018); new and improved monitoring technologies, especially those that improve understanding of factors that lead to injury and mortality (Egg et al 2018;Silva et al 2018); understanding the hydraulic conditions in and around hydropower plants and the effects in fish (Beirão et al 2018;Boys et al 2018;Colotelo et al 2018;Pflugrath et al 2018;Santos et al 2018); and determining long-term ecological impacts of hydropower plants and associated reservoirs (Cowx et al 2018;Loures and Pompeu 2018;Naughton et al 2018) These topics represent significant issues for hydropower developers and the content and solutions presented in these articles will help address key knowledge gaps in both tropical and temperate systems.…”