Run-of-river hydropower reduces streamflow between diversion and powerhouse, potentially impacting fish. Hydropower license conditions include instream flows to protect fish, but monitoring instream flow effectiveness to protect fish is rarely reported. Monitoring a trout population before construction (baseline) and during operation of a small hydropower project with instream flows for spawning and incubation, summer rearing, and winter rearing based on a Physical Habitat Simulation System in the state of Washington indicated the instream flow protected the trout. The monitoring plan included decision points based on monitoring results. Increasing or stable population trends would trigger locking in an instream flow for the remainder of the license, while declines would trigger incremental increases in the instream flow, followed by additional monitoring and decision points. Three years of monitoring following beginning of the project indicated an apparent increase in the trout population over baseline, suggesting that the instream flow was protective, triggering finalization of instream flows. An additional year of monitoring conducted after several more years of project operation was consistent with the finding of the first 3 years of operation.

中文翻译：

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监控鳟鱼对溪流的响应

河流上游水力发电减少了引水和发电站之间的水流，可能对鱼类产生影响。水电许可条件包括用于保护鱼类的流入水流，但是很少有关于监视流入水流有效性以保护鱼类的报道。根据华盛顿州的物理栖息地模拟系统，在小型水力发电项目建设前（基线）和运营过程中对鳟鱼种群进行监测，并利用溪流进行产卵和孵化，夏季饲养和冬季饲养，这表明流入溪流保护了鳟鱼。监控计划包括基于监控结果的决策点。人口趋势的增加或稳定会触发剩余许可证的流入流量，而下降会触发流入流量的增量，其次是其他监视和决策点。项目开始后的三年监测表明，鳟鱼种群数量明显超过基线，这表明河道水流具有保护性，触发了河床水流的最终确定。在项目运行了数年之后，又进行了一年的监视，这与运行前三年的发现是一致的。