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.
Sci Total Environ. 2021 May 10;768:144866. doi: 10.1016/j.scitotenv.2020.144866. Epub 2020 Dec 31.
The Three Gorges Reservoir (TGR) underwent staged impoundment of water from 135 m to 175 m between 2003 and 2010. Periodic water impoundment was divided into drainage (March to early June), low water level (June to August), impoundment (September to October), and high water level (November to February) period. However, the impact of the Three Gorges Dam (TGD) and staged impoundment on water quality, especially in the long term, remains unclear. Herein, hydrological, pollution load, nutrient, and biochemical indices were determined for the TGR during 1998-2018. The Canadian Council of Ministers of the Environment Water Quality Index, a K-means clustering algorithm, and the Mann-Kendall (MK) test were applied to this data to explore the spatial and temporal distribution of water quality. The results show that water quality was good overall, but it before the full impoundment stage (2010) was worse than after that. The low water level period had the worst water quality among the four periods, and spatially, midstream was worst. Among water quality indices, the median total nitrogen (TN) and total phosphorus (TP) were in the range of 1.505-2.303 and 0.071-0.176 mg/L, respectively, and these were the key pollution indices. In addition, due to differences in hydrological and hydrodynamic conditions, and the regional distribution of pollution sources, water quality in the TGR displayed temporal and spatial heterogeneity. TN, TP, potassium permanganate index (COD), five-day biochemical oxygen demand (BOD) and Escherichia coli (E. coli) were maximal during the low water level period, and TN, TP and E. coli were highest in midstream. MK test results revealed that nutrients pollution became worse midstream, and a gradual increase in TP caused severe algal blooms downstream. Therefore, nutritional water treatment and non-point source pollution control should be the focus of future work.
三峡水库（TGR）在2003年至2010年间经历了从135米到175米的分阶段蓄水。周期性蓄水分为排水期（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2月）。然而，三峡大坝（TGD）和分阶段蓄水对水质的影响，尤其是长期影响，仍不明确。在此，对1998 - 2018年期间三峡水库的水文、污染负荷、营养物质和生化指标进行了测定。将加拿大环境部长理事会水质指数、K均值聚类算法和曼-肯德尔（MK）检验应用于这些数据，以探索水质的时空分布。结果表明，总体水质良好，但在全面蓄水阶段（2010年）之前比之后更差。四个时期中低水位期水质最差，在空间上，中游水质最差。在水质指标中，总氮（TN）和总磷（TP）的中位数分别在1.505 - 2.303和0.071 - 0.176毫克/升范围内，这些是关键污染指标。此外，由于水文和水动力条件的差异以及污染源的区域分布，三峡水库的水质呈现出时空异质性。TN、TP、高锰酸钾指数（COD）、五日生化需氧量（BOD）和大肠杆菌（E. coli）在低水位期最高，TN、TP和E. coli在中游最高。MK检验结果显示，中游营养物质污染加剧，TP的逐渐增加导致下游严重的藻华现象。因此，营养水体处理和非点源污染控制应成为未来工作的重点。
