Abstract Hydropeaking is an anthropogenic regime that results from the strong flow variations in the receiving waters of storage hydropower plants. These variations are due to flexible energy production, i.e. the sudden increase of electricity demands or from its decrease, affecting the fish assemblages of that river stretch. We evaluated the mitigation potential of the hydropeaking diversion hydropower plant (hd-HPP) named Gemeinschaftskraftwerk Inn - GKI, located in the Inn River at the Alpine region (Tyrol, Austria). This HPP will use a weir reservoir for the retention of hydropeaking coming from upstream HPPs, together with the diversion of peak flows, which intends to mitigate the impacts of hydropeaking along the residual flow stretch while allowing for hydropower production. Our study aims to evaluate and mitigate the stranding potential of the European grayling (Thymallus thymallus) within the time range of the species' larvae life-stage in the Inn river's studied stretch. To do so, we addressed a set of high-resolution historical hydrological data and, afterwards, the implementation of mitigation operational scenarios, for wet and dry years. The performance of the historical status and the mitigation scenario was assessed based on 1D unsteady modelling in a set of 26 cross-sections along a 6.5 km stretch, by quantifying the downramping rate and flow ratio events over the grayling larvae's tolerance thresholds to stranding (0.2 cm/min) and the Austrian legal threshold for flow ratio (1:3), respectively. Furthermore, we developed a new eco-hydromorphological assessment scheme, including topographic features that have been confirmed as stranding increase factors, besides the hydrological parameter's assessment. A qualitative classification was defined (Very High, High, Medium, Small, Low) for the species' larvae stranding potential, gathering the hydrological and morphological parameters assessment, represented in a map with the cross-section's location and assessment class. Results confirmed that the operational scenario highly reduced the number of events where downramping rate and the flow ratio were over the thresholds in all sections, with higher effectiveness in the wet year analysis, where tributaries influence showed a major role. Afterwards, for the qualitative assessment, in the historical records analysis the cross-sections status were included in the High or Medium classes of stranding potential. In the mitigation scenarios, most of sections' status shifted to the Low or Small classes. With this study, we confirmed that the GKI hydropower scheme may be considered as an effective hydropeaking mitigation strategy. Additionally, we presented a novel 1D-based approach for stranding potential assessment, grounded on a cost-effective and integrative classification scheme.

中文翻译：

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导流水电站水峰缓解评估的新见解：GKI 项目（奥地利蒂罗尔）

摘要 水峰化是一种人为现象，它是由蓄水电站受纳水体的强烈流量变化引起的。这些变化是由于灵活的能源生产，即电力需求的突然增加或减少，影响了该河段的鱼类组合。我们评估了名为 Gemeinschaftskraftwerk Inn - GKI 的水峰分流水电站 (hd-HPP) 的减缓潜力，该电站位于阿尔卑斯地区（奥地利蒂罗尔）的因河。该 HPP 将使用堰式水库来保留来自上游 HPP 的水峰，以及峰值流量的分流，旨在减轻沿剩余流段的水峰影响，同时允许水电生产。我们的研究旨在评估和减轻欧洲鳟鱼 (Thymallus thymallus) 在因河研究河段的物种幼虫生命阶段的时间范围内的搁浅潜力。为此，我们处理了一组高分辨率的历史水文数据，然后针对干湿年份实施了缓解操作情景。历史状态和缓解方案的性能是基于沿 6.5 公里长的一组 26 个横截面中的一维非定常建模进行评估的，方法是量化比鳟鱼幼虫搁浅耐受阈值 (0.2 cm/min) 和奥地利法定流量比阈值 (1:3)。此外，我们开发了一个新的生态水文形态评估方案，除水文参数评估外，还包括已确认为搁浅增加因素的地形特征。为该物种的幼虫搁浅潜力定义了定性分类（非常高、高、中、小、低），收集水文和形态参数评估，在带有横截面位置和评估类别的地图中表示。结果证实，运行情景大大减少了所有断面下坡率和流量比超过阈值的事件数量，在支流影响显示出主要作用的丰水年分析中具有更高的有效性。之后，对于定性评估，在历史记录分析中，横截面状态被包括在搁浅潜力的高或中类中。在缓解方案中，大多数部分的状态转移到低级或小级。通过这项研究，我们确认 GKI 水电计划可被视为一种有效的水峰缓解策略。此外，我们提出了一种基于成本效益和综合分类方案的搁浅潜在评估的基于一维的新方法。