受强人类活动和极端洪旱气候等因素综合影响,长江中下游江湖水沙情势、冲淤分布及江湖关系等均发生改变。三峡水库蓄水后,长江中下游干流年均输沙量大幅减少,减幅达70%~93%,年内流量过程总体有所坦化,但汛后因水库群蓄水而退水速率加快;洞庭湖四水及荆江三口年均入湖径流量无明显变化,入湖沙量呈减少趋势,入湖年均水、沙量分别减少了9%和38%;鄱阳湖五河年均入湖水、沙量分别减少了2%和57%,出湖年均水、沙量分别增多了1%和5%。水沙过程的改变引起长江中下游冲淤格局变化,2003—2021年长江中下游河段累计冲刷50.3亿m³,年均冲刷量2.65亿m³;洞庭湖区由淤积转为微冲,荆江三口洪道以冲刷为主;鄱阳湖区总体上由淤转冲,入江水道冲刷下切明显。未来30 a长江中下游干流河道仍将保持冲刷态势,至2050年末宜昌至大通河段、荆江三口洪道累计冲刷量分别为35.8亿m³和1.17亿m³,洞庭湖区呈微淤状态,鄱阳湖区呈微冲状态。基于长江中下游江湖冲淤新格局,从防洪、供水、航运、生态及涉水建筑物安全等5个方面,较为系统地阐述了江湖演变的影响效应,并针对性地提出了若干对策和建议。

在气候变化、人类活动导致流域水循环改变、极端水文事件频发的背景下,从江湖关系角度分析鄱阳湖水文节律变化规律,对于维护流域水安全具有重要意义。利用1951~2011年湖区4站及湖口站水文实测资料,采用统计分析及水文过程分析方法,对湖泊水文节律在2003~2011年与1980~2002年发生的显著变化及其与长江水量交换的关系进行研究。结果表明：2003~2011年,湖泊因涨、退水阶段水位均偏低,进而枯水阶段延长,同时丰水阶段缩短,湖泊水文节律整体呈现洪旱急转情势;近年来江湖水量交换的变化是造成湖泊水文节律变化的主要原因。

Watershed hydrological cycle has been changed along with the intensifying frequency of extreme water events due to the influence of climate change and human activities. Poyang Lake, the largest freshwater lake in China, is a lake naturally connected with the Changjiang River. The complicated river-lake interactions impact the hydrological rhythm of lake, which will further influence water security associated with flood control, drinking water usage, water pollution and water ecology in the lake basin. In the case, it is of great importance for maintaining watershed water security to understand the characteristics of hydrological rhythm variation in terms of river-lake interactions. In this study, temporal variation of hydrological rhythm in Poyang Lake and the associated water exchange with the Changjiang River were analyzed based on the measured hydrological data of 4 gauge stations in Poyang Lake area along with other data from the Hukou station at the intersection between the Changjiang River and Poyang Lake in 1951-2011. The major findings are shown as follows: the span of dry season increased since water level remains low in November and April. Meanwhile, the span of flood season decreased in 2000s. The lower water level in rising season and retreating season make Poyang Lake rising later but falling earlier than they did in 1980-2002, thus shortening the conversion time of the lake from flood situation to dry situation. Further, the peak flow in the annual hydrograph has been shifted. The primary cause of hydrological rhythm variation is the water exchange between the main stream of the Changjiang River and Poyang Lake. In 2000s, changes in the water level of the Changjiang River altered the interaction between the river and Poyang Lake through the slope of water surface, disturbing the lake basin hydrological processes and resulted in disordering of hydrological rhythm in Poyang Lake. The increasing discharge from the lake to the river in retreating season lead to the lake enter dry season earlier. And the declining water level of Changjiang River in rising season lead to the addition of lake water continued to leak river, thus the lake rose slowly. For the reasons given above, the variation of water supplement of Poyang Lake on the Changjiang River mainstream in 2000s altered the hydrological rhythm in Poyang Lake. Results of this study improve our understanding of Poyang Lake hydrological rhythm consequences of river-lake relationship changes, and it provides knowledge for long-term planning for effectively restoring nature's innate rhythms for sustainability and productivity in the Poyang Lake Basin. In addition, the results will help further explore the coordinate and healthy river-lake relationships.

Sediment problem is one of the key factors which affect the dispatching operation and life of the Three Gorges Project (TGP). Many approaches were employed to research the sediment problems of the TGP during its demonstration, planning, design, construction and operation, and many important results were obtained. It was confirmed that the previous sediment research results are reasonable and reliable by analyzing the field data of the actual testing operation of TGP. The 10-year operation of TGP shows that the basic situation of sediment problems is good, and the local problems were or are in control through proper treatment. However, these sediment problems can probably accumulate, develop and transform with time, so they should be paid continuous attention. The influence of the TGP operation on the relationship between rivers and lakes was also analyzed in this paper. It was pointed out that intense and large-scale erosion happens in the downstream channel of the dam since TGP operation, and the water levels at the outlets of Dongting Lake and Poyang Lake have decreased, which has some influence on the water and sediment diversions and results in sharp contradiction of water resource supply and demand in dry season for both lakes. It is effective and feasible to solve the existing problems through constructing sluices and other measures in the Dongting Lake and the Poyang Lake.

鄱阳湖与长江之间存在着复杂的相互作用关系,决定着江湖水沙交换,对整个区域的水资源、防洪、航运、生态环境等均具有重要影响。本文基于能量的观点,在从新的角度解释鄱阳湖和长江相互作用原理的基础上,构建了江湖相互作用的表征指标—能差F_e,对20世纪50年代以来江湖作用关系变化进行了研究。结果表明,自20世纪50年代以来,F_e值整体呈现增加趋势,说明长江作用减弱,鄱阳湖作用不断增强。三峡水库蓄水运用对江湖关系产生了重要影响,进一步削弱了长江作用。从年内变化来看,由于三峡水库的调节,枯水期长江作用略有增强,汛末长江作用减弱较大。江湖作用一定程度上影响着湖区旱涝灾害的产生,当五河来流较大且长江顶托作用明显时,易发生洪涝;当五河来流较小但又对长江有明显的补水作用时,易发生旱情,三峡水库蓄水使湖区9-10月更易发生干旱。

The complicated relationship between the Yangtze River and Poyang Lake is the factor determining the exchange of water and sediment between them and has great influence on the water resources, flood control, navigation, and ecological environment of the entire region. Based on the theory of energy, this paper explains the principle of the river-lake relationship from a new perspective. By constructing a new index F_e, the authors were able to analyze the evolution of the relationship between the Yangtze River and Poyang Lake since the 1950s. The results indicate that the value of F_e shows an increasing trend, which means the river effect is weakening while the lake effect is strengthening. Operation of the Three Gorges Dam has an important impact on the river-lake relationship, which further weakens the river effect. The river effect increases slightly in the dry season but decreases significantly at the end of the flood period. In addition, the relationship between the Yangtze River and Poyang Lake may induce drought and flood disasters to some degree. Flooding is more likely to occur when flow from the five tributaries of the Poyang Lake is large and the Yangtze River blocking effect is strong. In contrast, drought is more likely to occur when flow from the five tributaries of the Poyang Lake is small, while the lake effect is strong. Meanwhile, the probability of drought in the Poyang Lake from September to October increases due to the impounding of the Three Gorges Reservoir.

河流交汇区是河网系统中水、沙、污染物、生物等环境要素的突变点,也是河网行洪与污染物输移扩散的关键控制节点。从野外测量、室内试验与数值模拟方面,总结分析了河流交汇区水流结构与污染物输移的基本特征及其在不同交汇条件作用下的响应规律,以及复杂水流结构与生境对于河流交汇区水安全的重要影响。展望了未来研究重点,建议加强非恒定流条件下的交汇区水力学特性研究,进一步揭示交汇区污染物掺混输移特征与水动力条件之间的响应机制,研究通过工程布局与水力优化调控相结合的措施系统提升了交汇区防洪安全与水生态环境质量。