On the cumulative dam impact in the upper Changjiang River: Streamflow and sediment load changes
On the cumulative dam impact in the upper Changjiang River: Streamflow and sediment load changes
复制标题
长江上游径流量及输沙量变化对大坝累积影响的探讨
DOI：
10.1016/j.catena.2019.104250
复制
发表时间：
2020-01-01
期刊：
影响因子：
6.2
通讯作者：
Zhou, Yinjun
中科院分区：
文献类型：
--
作者：
Guo, Chao;Jin, Zhongwu;Zhou, Yinjun
气候变化和人类活动，如大坝建设改变流域尺度的河流水文情势。长江上游是继三峡大坝建成后世界上筑坝最多的河流之一。量化大坝的累积影响是更好地管理河流的先决条件。在这项工作中，我们根据1950 - 2017年的数据，在整个uCR的多个时间尺度上对径流量，泥沙负荷和泥沙成分的变化进行了严格的评估。我们观察到，自2015年以来，在宜昌（uCR流域的出口），年径流量出现了减少的趋势，尽管前65年的变化在统计上并不显著。年输沙量逐渐大幅度减少，与20世纪50年代相比，2010年增长了97%。2003年和2014年，三峡大坝和上游干流新建大坝分别加速了输沙量的减少。结果，悬浮泥沙变得更细，平均粒径从1960年代的17 μ m减少到2010年代的8 μ m。我们建立了一个水库蓄水能力指数，这是总水库蓄水量与年径流量的比率，并确定了一个阈值为4%，大于该阈值的累积大坝的影响将导致深刻的泥沙减少。我们的结论是，气候变化和人类活动，特别是在mainstem的大型水坝，改变了uCR系统从一个动荡和泥泞的河流平静的，这可以影响河流的过程，以及通过改变沉积物和营养盐的浓度和比例的水生生态系统。这些水文形态的变化值得有关当局的紧急关注。
Climate change and anthropogenic activities such as dam construction alter basin-scale hydrological regime of a river. The upper Changjiang River (uCR) stands out as one of the most heavily dammed rivers in the world after the construction of the Three Gorges Dam (TGD) and other large dams in its mainstem. Quantification of the cumulative dam impact is prerequisite for better river management. In this work, we provide a rigorous appraisal of the changes in streamflow, sediment load, and sediment composition at multiple time scales throughout the uCR based on data in 1950-2017. We observed that a decreasing trend in annual streamflow has emerged since 2015 at Yichang, the outlet of the uCR basin, although the changes were statistically insignificant for the first 65 years. The annual sediment load has decreased progressively and substantially, e.g., by 97% in 2010s compared to 1950s at Yichang. The Three Gorges Dam and the new large dams in the upstream mainstem accelerated the sediment load reduction in 2003 and 2014, respectively. As a result, the suspended sediment became finer, with a decrease in mean diameter from 17 mu m in the 1960s to 8 mu m in the 2010s at Yichang. We established a reservoir storage capacity index, which is the ratio of the total reservoir storage capacity to annual streamflow, and identified a threshold of 4% larger than which the cumulative dam impact will induce profound sediment load reduction. We concluded that climate change and anthropogenic activities, in particular the large dams in the mainstem, have transformed the uCR system from a turbulent and muddy river to a placid one, which can affect fluvial processes as well as aquatic ecosystems by altering sediment and nutrient concentrations and ratios. These hydro-morphological changes merit the urgent attention of concerned authorities.