This study identifies hydrodynamic alterations in flow downstream of a dam that are related to hydropower plant (HPP) operation and that might attract Neotropical potamodromous fish to unsafe places in the tailrace during their reproductive migration. Our hypotheses are (1) the hydrodynamic flow in the tailrace presents conditions that are strong attractive for fish than those found in the downstream reach and (2) there are no velocity barriers preventing the upstream migrant from reaching the tailrace over a wide range of turbine discharge. Two calibrated numerical models were created for the Tres Marias HPP (Brazil), using different turbine discharges: (1) a three-dimensional (3D) model of flow in the tailrace and (2) a two-dimensional (2D) model for flow in the 3-km reach downstream of the dam. Resulting flow fields of the Tres Marias HPP tailrace have elevated hydraulic strain and velocity homogeneity by as compared to the flow field of the downstream reach. The tailrace velocities are slow for mature individuals of all study species, which may swim from downstream reach to unsafe areas in their sustainable and prolonged mode by available corridors for different turbined discharges.

中文翻译：

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水电站运行对下游水动力场的改变：对上游鱼类洄游的影响

这项研究确定了与水电站 (HPP) 运行相关的大坝下游水流的水动力变化，这些变化可能会在繁殖迁移过程中将新热带河豚吸引到尾水道中不安全的地方。我们的假设是 (1) 尾水道中的流体动力流动呈现出的条件比下游河段中的条件对鱼类更具吸引力；(2) 没有速度障碍阻止上游移民通过广泛的涡轮机到达尾水道释放。为 Tres Marias HPP（巴西）创建了两个校准数值模型，使用不同的涡轮机排放量：(1) 尾水道中流动的三维 (3D) 模型和 (2) 流动的二维 (2D) 模型在大坝下游 3 公里处。与下游河段的流场相比，Tres Marias HPP 尾水道产生的流场提高了水力应变和速度均匀性。所有研究物种的成熟个体的尾流速度都很慢，它们可能会通过不同涡轮排放的可用走廊以可持续和延长的模式从下游到达不安全区域。