三峡水库蓄水后,长江中下游物理生境发生明显变化,一定程度上影响河流功能的发挥。采用资料分析和文献综述,研究了三峡水库蓄水运用后长江中下游水文条件、河道形态、植被等典型物理生境的变化,总结了其对防洪、航道条件、供水、典型水生生物的影响。提出了应加强研究内容:①监测方面,包括长江中下游系统性和长期性监测、河(航)道治理工程、生态调度试验效果监测等。②规律和机理方面,包括河道形态变化机制和共性规律、干流洲滩植被变化机制、长江中下游洪水位和底栖动物对物理生境变化的响应规律和阈值等。③方法和对策方面,包括多因素影响下长江中下游水文条件中长期变化趋势预测方法,适应物理生境变化并满足需求的整治技术,满足供水、底栖、鱼类繁殖等目标的水库优化调度方案等,物理生境变化-影响效应-改善策略和技术全过程一体化研究。研究成果可为长江大保护及其健康发展提供参考。

The physical habitat of the middle and lower reaches of the Yangtze River has experienced significant changes after the impoundment of the Three Gorges Reservoir, thereby affecting river functions. Based on data analysis and literature review, this paper examined the alterations in typical physical habitats such as the hydrological condition, river morphology, and vegetation after the TGR operation and their subsequent impacts on flood prevention, navigation, water supply, and typical aquatic organisms. Key areas for further research were identified as follows: 1) monitoring, including systematic and long-term monitoring programs, and the assessment of the effectiveness of river (waterway) management projects and ecological regulation measures; 2) laws and mechanisms of changes in river morphology, vegetation in the main stream and shoals, and the responses and thresholds of flood levels and benthic animals to variations in the physical habitat; 3) methods for predicting medium and long-term trends of hydrological conditions under the influence of multiple factors, channel regulation technologies that adapt to changes in the physical habitat and meet demands, as well as reservoir operation schemes that align with water supply objectives, benthic animal and fish breeding needs. Additionally, integrated research efforts focusing on physical habitat changes, their impacts, and improvement strategies and technologies require increased attention.

Poyang lake floodplains are hydrologically complex and dynamic systems which exhibit dramatic intra-annual wetting and drying. The flow regime of the Yangtze River was previously known to play an important role in affecting Poyang Lake and its extremely productive floodplains (river–lake relationship). The recent severe declines and recessions in the lake are closely linked to the changed river–lake relationship, resulting in significant hydrological, ecological, and economic problems. This study aims to examine the spatiotemporal heterogeneity of the floodplain hydrodynamic behaviors with respect to impacts of the changed river–lake relationship, characterized by the lake water level, inundation area, and inundation duration based on a floodplain hydrodynamic model of Poyang Lake, and to further quantify the severity of dryness recently endured since 2000. Simulation results show that, in general, the current modified river–lake relationship is more likely to affect the hydrological seasonality of the floodplain system since 2000, relative to the flooding and drying cycles during past decades (1953–2000). The present hydrodynamic behaviors suffered significant change due to the greatest interference from the altered river–lake relationship, particularly for the falling period in October. On average, the floodplain water level and inundation duration decreased by 6 m and 12 days during October, respectively. Additionally, the highest monthly shrinkage rate in floodplain inundation shifted from the period of October–November to September–October, with the mean inundation area decreasing by around 50%, demonstrating an advanced and prolonged dry condition. The spatial responses of the hydrodynamics in the low-slope floodplains are most likely to be affected by the dynamic river–lake relationship, as expected. This study assessed the effects of the altered river–lake relationship on the hydrological regime of the Poyang Lake floodplains in terms of spatiotemporal distributions and changing processes for the periodic inundated behavior, which can support the relevant study of the subsequent ecological effects on the wetlands.

为科学定量评价三峡水库运行过程对洞庭湖径流及生态特征的影响,收集城陵矶、石龟山、南咀、小河咀4个水文站1988—2020年逐日流量数据,应用IHA-RVA法和Shannon指数法对三峡水库试运行阶段(2003—2008年)和三峡试运行后阶段(2009—2020年)流量演变和生态效应进行定量分析。结果表明:①三峡水库运行过程中汇入洞庭湖流量占比方面,湘、资、沅、澧四水占比持续提高,荆江三口占比持续下降;②三峡水库蓄水试运行阶段洞庭湖区水文站整体流量改变度和IHA高度改变指标个数高于三峡水库试运行后阶段,且城陵矶和石龟山整体改变度分别达到67.27%和69.55%,形成高度改变;③三峡水库试运行阶段,三峡水库蓄水下游流量上涨次数及上涨幅度减少,连续日流量正差异值R_rate减少,洞庭湖Shannon指数均有下降趋势;三峡水库试运行后阶段按“枝城调度”规则运行保证三峡次数下游有中小洪水过程并增加下游枯水补给,R_rate增加、Shannon指数有所回升。研究成果可为洞庭湖水安全和水生态健康提供科学依据。

To scientifically and quantitatively evaluate the impact of Three Gorges Reservoir operations on the runoff and ecological characteristics of Dongting Lake, we analyzed daily flow data from four hydrological stations—Chenglingji, Shiguishan, Nanzui, and Xiaohezui—spanning 1988 to 2020. We employed the IHA-RVA method and Shannon index method to assess flow evolution and its ecological effects during the trial operation phase (2003-2008) and the post-trial operation phase (2009-2020) of the Three Gorges Reservoir. Our findings indicate that: (1) During the operation of the Three Gorges Reservoir, the proportions of water flowing into Dongting Lake from the Xiangshui River, Zishui River, Yuanjiang River, and Lishui River increased, while the proportions from the three outlets of Jingjiang River decreased.(2) In the trial operation phase, the overall changes in flow rate and IHA were greater than those in the post-trial phase, with Chenglingji and Shiguishan exhibiting overall changes of 67.27% and 69.55%, respectively.(3) During the trial operation phase, a reduction in the magnitude of downstream flow increases led to a decrease in both the daily flow rate positive difference (R_rate) and the Shannon index. However, in the post-trial phase, adherence to the “Zhicheng Dispatch” rules, which aimed to ensure small and medium-sized floods downstream and increase dry-season water supply, led to an increase in R_rate and a rebound in the Shannon index. These results provide a scientific basis for ensuring water safety and ecological health in Dongting Lake.

三峡水库自2003年开展蓄水调度以来,已运行20 a,在防洪、发电、航运、水资源利用、生态环境保护等方面发挥了重要作用,但也对下游水文情势产生影响。选择宜昌水文站1950—2022年逐日径流和水位资料,采用MASH滑动平均法、Sen斜率估计法和IHA/RVA法量化评估三峡水库投运以来宜昌水文站水文情势改变程度。研究结果表明:宜昌水文站1—5月份滑动平均流量序列呈现显著上升趋势,9—11月份滑动平均流量序列呈现显著下降趋势,而6—12月份滑动平均水位呈现显著下降趋势;宜昌水文站合计有14个水文改变指标(IHA)发生了高度水文情势改变,整体综合改变度为63.52%,属于中度改变;三峡水库通过径流调蓄,显著增加了年最小流量组分的中值和流量折转次数,且减少年最大1 d流量的中值,进一步反映了三峡水库防洪兴利的综合效益。研究结果可为三峡水库水资源综合管理提供参考依据。

The Three Gorges Reservoir, impounded since 2003 for 20 years, has played a crucial role in flood prevention, hydropower generation, navigation, water resource utilization, and ecological environmental protection. However, its operation has also impacted downstream hydrological regimes. We analyzed daily runoff and water level data from the Yichang hydrological station spanning from 1950 to 2022. Applying the MASH (Moving Average over Shifting Horizon), Sen slope, and IHA/RVA methods, we quantitatively assessed the alterations in hydrological regimes following the Three Gorges Reservoir operation. Findings revealed significant trends in moving-average runoff, with increases during January-May and decreases during September-November, as well as decreasing moving-average water levels from June to December. Fourteen IHA (Indicators of Hydrologic Alteration) showed substantial alterations, resulting in an overall alteration of 63.52%, classified as moderate. The Three Gorges Reservoir notably enhanced the median values of annual minimum flow components and the number of flow reversals while decreasing the median values of annual maximum 1-day flow through streamflow regulation. These adjustments reflect the reservoir’s multifaceted benefits for flood control and hydropower generation. The research outcomes offer valuable insights for managing water resources within the Three Gorges Reservoir.

This study proposes a framework for estimating pollutant flux in an estuary. An efficient method is applied to estimate the flux of pollutants in an estuary. A gauging station network in the Danshui River estuary is established to measure the data of water quality and discharge based on the efficient method. A boat mounted with an acoustic Doppler profiler (ADP) traverses the river along a preselected path that is normal to the streamflow to measure the velocities, water depths and water quality for calculating pollutant flux. To know the characteristics of the estuary and to provide the basis for the pollutant flux estimation model, data of complete tidal cycles is collected. The discharge estimation model applies the maximum velocity and water level to estimate mean velocity and cross-sectional area, respectively. Thus, the pollutant flux of the estuary can be easily computed as the product of the mean velocity, cross-sectional area and pollutant concentration. The good agreement between the observed and estimated pollutant flux of the Danshui River estuary shows that the pollutant measured by the conventional and the efficient methods are not fundamentally different. The proposed method is cost-effective and reliable. It can be used to estimate pollutant flux in an estuary accurately and efficiently.