CD-Laboratory for Sediment Research and Management, Institute of Hydraulics and River Sciences, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences Vienna, Muthgasse 107, 1190 Wien, Austria.
CD-Laboratory for Sediment Research and Management, Institute of Hydraulics and River Sciences, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences Vienna, Muthgasse 107, 1190 Wien, Austria.
Sci Total Environ. 2023 Jul 20;883:163667. doi: 10.1016/j.scitotenv.2023.163667. Epub 2023 Apr 24.
Hydropeaking is one of the major hydropower-related disturbances of natural processes in river systems. The artificial flow fluctuations that are caused by the on-demand production of electricity are known for their severe impacts on aquatic ecosystems. These particularly affect those species and life stages that are not able to adjust their habitat selection to rapid up- and downramping rates. To date, the stranding risk has both experimentally and numerically mainly been investigated with variable hydropeaking graphs over stable river bathymetries. There is a lack of knowledge on how single, discrete peaking events vary concerning their impact on the stranding risk when the river morphology changes in the long-term perspective. The present study precisely addresses this knowledge gap by investigating morphological changes on the reach scale over a period of 20 years and the related variability of the lateral ramping velocity as a proxy for stranding risk. Two alpine gravel bed rivers impacted by hydropeaking over decades were tested by applying a one-dimensional and two-dimensional unsteady modelling approach. Both the Bregenzerach River and the Inn River exhibit alternating gravel bars on the reach scale. The results of the morphological development, however, showed different developments in the period 1995-2015. The Bregenzerach River displayed continuous aggradation (uplift of river bed) over the various selected submonitoring periods. In contrast, the Inn River showed continuous incision (erosion of river bed). The stranding risk exhibited high variability on a single cross-sectional basis. However, on the reach scale, no significant changes in stranding risk were calculated for either river reach. In addition, the impacts of river incision on the substrate composition were investigated. Here, in line with preceding studies, the results show that the coarsening of substrate increases the stranding risk and that especially the d (90 % finer of the grain size distribution) must be considered. The present study reveals that the quantified stranding risk of aquatic organisms is a function of the general morphological (bar) characteristics of the impacted river and both the morphological and grain size development have an impact on the potential stranding risk of aquatic organisms and should be considered in the revision of licences in the management of multi-stressed river systems.
水力发电是河流系统中与水力发电相关的主要自然过程干扰之一。按需发电导致的人工水流波动对水生生态系统造成了严重影响。这些波动特别影响那些无法调整栖息地选择以适应快速上升和下降坡度的物种和生命阶段。迄今为止，搁浅风险主要通过在稳定河底地形上使用可变水力发电图进行实验和数值研究来进行研究。当从长期角度来看河流形态发生变化时，关于单个离散峰值事件如何因其对搁浅风险的影响而变化的知识还很缺乏。本研究通过在 20 年的时间内调查河道尺度上的形态变化以及作为搁浅风险代理的侧向变坡速度的相关变异性，精确地解决了这一知识差距。应用一维和二维非稳态建模方法对几十年受到水力发电影响的两条高山砾石河床河流进行了测试。布雷根茨河和因河在河道尺度上都有交替的砾石滩。然而，形态发育的结果在 1995-2015 年期间显示出不同的发展。布雷根茨河在各个选定的次监测期间连续淤积（河床抬升）。相比之下，因河则持续下切（河床侵蚀）。在单个横截面基础上，搁浅风险表现出高度的可变性。然而，在河道尺度上，两条河道都没有计算出搁浅风险的显著变化。此外，还研究了河流下切对底质组成的影响。在这里，与先前的研究结果一致，结果表明底质变粗会增加搁浅风险，特别是 d（粒度分布的 90%细部分）必须考虑在内。本研究表明，水生生物的量化搁浅风险是受受影响河流的一般形态（滩）特征以及形态和粒度发展影响的函数，并且应该在多胁迫河流系统管理许可证修订中考虑到这一点，以降低搁浅风险。
