Institute for Water Management, Hydrology and Hydraulic Engineering, Department for Water-Atmosphere-Environment, BOKU - University of Natural Resources and Life Sciences Vienna, Muthgasse 107, 1190 Vienna, Austria.
Institute for Water Management, Hydrology and Hydraulic Engineering, Department for Water-Atmosphere-Environment, BOKU - University of Natural Resources and Life Sciences Vienna, Muthgasse 107, 1190 Vienna, Austria.
Sci Total Environ. 2017 Jan 1;575:1503-1514. doi: 10.1016/j.scitotenv.2016.10.031. Epub 2016 Oct 26.
Hydropeaking is one of the main pressures on the aquatic ecology in alpine rivers. Beside studies on abiotic process and biotic response on the local scale there is a lack in process understanding on the reach scale. Especially longitudinal changes of hydropeaking impacts based on retention processes have not been studied yet. Thus, based on unsteady one-dimensional and two-dimensional depth averaged modelling it was targeted to investigate possible changes in vertical ramping velocity for the discussion of possible mitigation measures at the local scale. Here, we compared artificial and natural sheltering habitats in terms of peak flow. Additionally, the hydropeaking assessment on various river scales was supported by an evaluation of tributaries in an alpine river system. Based on the modelling results and the discussion of the impact assessment of hydropeaking in different case studies we state, that on the first 5km downstream of the turbine outlet a significant decrease in vertical ramping velocity occurs. In this reach, habitat improvements should focus on increasing retention processes considering the higher risk of stranding for juvenile fish and macroinvertebrates. For morphological mitigation measures at the local scale, it turned out that self-formed, near-natural morphology should be targeted in terms of mitigation measure design compared to artificial sheltering habitats. Abundance and biomass of macroinvertebrates are directly linked to substrate variability in self-formed sheltering habitats downstream of gravel bars. Moreover, we ascertained that tributaries are able to contribute to the 'ecological potential' in multi-stressed hydropeaking rivers by providing spawning and rearing habitats for fish. However, for a sustainable improvement of the aquatic environment on all relevant scales, both sediment and flood dynamics have to be considered as important drivers to establish self-formed sheltering habitats in terms of hydropeaking.
水跃是高山河流中对水生生态系统的主要压力之一。除了对当地尺度上的非生物过程和生物响应进行研究外，对水流过程的理解还存在不足。特别是基于滞留过程的水跃影响的纵向变化尚未得到研究。因此，本研究基于非稳态一维和二维深度平均模型，旨在研究垂直变坡速度的可能变化，以讨论局部尺度上的可能缓解措施。在这里，我们比较了人工和自然庇护生境在峰值流量方面的差异。此外，还通过评估高山河流系统中的支流，对各种河流尺度的水跃进行了评估。基于模型结果和不同案例研究中水跃影响的评估，我们指出，在涡轮机出口下游的前 5 公里处，垂直变坡速度显著下降。在这个区域，生境改善应重点考虑增加滞留过程，以降低幼鱼和大型无脊椎动物搁浅的风险。对于局部尺度的形态缓解措施，与人工庇护生境相比，设计缓解措施时应针对自形成的近自然形态。自形成的庇护生境下游的砾石滩的基质变异性与大型无脊椎动物的丰度和生物量直接相关。此外，我们还确定了支流通过为鱼类提供产卵和育肥栖息地，能够为多压力水跃河流的“生态潜力”做出贡献。然而，为了在所有相关尺度上可持续改善水生环境，都必须考虑泥沙和洪水动力作为建立水跃条件下自形成庇护生境的重要驱动因素。
