Hydraulic factors influencing tropical fish movement in hydropower plant tailraces

Hydroelectricity is a significant source of electricity in many countries around the world. Blockage of fish migration routes is an environmental impact caused by hydroelectric power plants and schools of fish can accumulate in regions of the tailrace with no mitigation measures in place. The present work analyzed the influence of hydraulic conditions in a tailrace on fish presence in the Três Marias Hydroelectric Power Plant (Brazil). There, seven tons of fish were killed in 2007 during turbine shutdown and spillway opening. We generated a 3D hydrodynamic model in the Fluent software that compared velocity magnitude, vorticity magnitude, turbulent kinetic energy, turbulence intensity, dissipation of turbulent energy and hydraulic strain rate along the flow to the presence of Pimelodus maculatus (Mandi) and Prochilodus argenteus (Curimba) obtained during previous acoustic telemetry studies. The results indicated a higher fish presence near Turbine 1, whose values of velocity, vorticity and hydraulic strain were higher than other regions, despite similar turbine discharges. The factorial analysis for mixed data found that the combination of turbulent kinetic energy, dissipation of turbulent energy, turbulence intensity and vorticity explained 34.8 ​% of the variance, followed by the combination of hydraulic rate, vorticity and velocity at 21.3 ​%. Hydrodynamic conditions experienced by both fish species differed. For example, Mandi navigated in areas with diverse hydraulic patterns. Overall, a combination of hydraulic variables attracts both species to the Turbine 1 area, an unsafe region for shoals. • Few studies have addressed the effects of turbulence on the behavior of tropical fish species. • Flow velocity is considered the main explanatory factor of fish movement in tailraces. • Two techniques were combined: 3D acoustic telemetry and CFD modeling. • More than 50 ​% variation in fish presence in the tailrace was due to velocity and turbulent flow aspects. • Incorporating higher-order flow aspects may improve analyses of fish migratory behavior.