Xiang Rong, Wang Lijing, Li Hong, Tian Zebin, Zheng Binghui
National Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; School of Environment, Tsinghua University, Beijing 100084, China.
National Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Water Res. 2021 May 1;195:116993. doi: 10.1016/j.watres.2021.116993. Epub 2021 Mar 2.
The Three Gorges Reservoir (TGR) underwent staged impoundment during 2003-2010. Periodic water impoundment included drainage (March to early June), low water level (June to August), impoundment (September to October), and high water level (November to February) periods. However, the impacts of the Three Gorges Dam (TGD) and impoundment on water quality of TGR tributaries remain poorly understood, especially in the long term and across the entire TGR drainage basin. Herein, water quality and hydrological indices of 27 tributaries, eutrophication of 38 tributaries, and pollution load of the TGR were determined during 2000-2015 to explore spatiotemporal variations in water quality. The results revealed slower flow velocity in tributaries and an extended residence time with the water level rising, and the water quality of tributaries was mainly affected by the mainstream backwater movement. Water quality was good in more than 60% of tested sites, had the best condition in the impoundment period, and it increased over time. Spatially, water quality in tributary upstream was better than in the backwater area, and worst in the tributary estuary. Among water quality indices, total nitrogen (TN) and total phosphorus (TP) were the key pollution indices, with median range of 1.619-2.739 and 0.088-0.277 mg/L, respectively. Additionally, water quality indices of TGR tributaries displayed temporal and spatial heterogeneity due to different hydrodynamic and pollution load conditions. A total of 38 tributaries displayed eutrophication, the frequency of blooms concentrated in spring and increased from the upper tributaries to the downstream area. These results expanded the theory of hydrodynamic variation and the associated evolution of the water environment after impoundment, could provide theoretical references for water quality management in river-type reservoir.
三峡水库在2003年至2010年期间进行了分期蓄水。周期性的水位变动包括排水期（3月至6月初）、低水位期（6月至8月）、蓄水期（9月至10月）和高水位期（11月至次年2月）。然而，三峡大坝及蓄水对三峡水库支流水质的影响仍知之甚少，尤其是从长期来看以及在整个三峡水库流域范围内。在此，我们测定了2000年至2015年期间27条支流的水质和水文指标、38条支流的富营养化情况以及三峡水库的污染负荷，以探究水质的时空变化。结果表明，随着水位上升，支流流速减缓，停留时间延长，支流的水质主要受干流回水运动影响。超过60%的测试点位水质良好，在蓄水期水质状况最佳，且水质随时间有所改善。在空间上，支流上游水质优于回水区域，支流河口水质最差。在水质指标中，总氮（TN）和总磷（TP）是关键污染指标中位数范围分别为1.619 - 2.739毫克/升和0.088 - 0.277毫克/升。此外，由于不同的水动力和污染负荷条件，三峡水库支流的水质指标呈现出时空异质性。共有38条支流出现富营养化，水华发生频率集中在春季，且从支流上游向下游区域增加。这些结果拓展了蓄水后水动力变化及相关水环境演变的理论，可为河流水库水质管理提供理论参考。
