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.

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.

在广泛查阅国内外相关文献的基础上,对长江中下游两大通江湖泊洞庭湖与鄱阳湖水沙输移规律、冲淤演变规律及对洪枯调控功能的影响这3个方面的研究进展进行了总结分析,并对当前研究中存在的不足提出了今后应加强的内容,主要包括:①自然和人为影响下两湖演变机制量化揭示,包括资料匮乏时期两湖的演变过程、各种自然因素对两湖冲淤演变的影响的识别、人类活动加剧时期两湖的自然冲淤过程等;②两湖未来长历时、大范围冲淤情势变化趋势预测,实现从两湖泥沙淤积总量预测到淤积时空分布格局变化预测转变;③两湖演变对洪枯调控功能影响的指标化评估,包括表征湖泊洪枯调控功能的指标研究及其与两湖未来不同冲淤情景的响应关系等方面。

On the basis of extensive review of relevant literatures in China and abroad, we summarize and analyse the research progresses on three hot issues concerning two river-connecting lakes in the middle and lower reaches of the Yangtze River, namely, the Dongting Lake and the Poyang Lake. Such issues include: water and sediment transport law, erosion and deposition evolution law, and their impacts on flood/dry regulation function. We also put forward such aspects to be strengthened corresponding to the shortcomings of current research as follows: 1) the quantitative evolution mechanism of the two lakes under natural and human influences, including the evolution of the two lakes in the period of scarce data, identification of the impact of natural factors on the erosion/deposition of the two lakes, and the natural erosion/deposition of the two lakes in the period of intensified human activities, etc; 2) forecasting the trend of long-term and wide-range erosion and deposition of the two lakes, transforming from total sediment deposition forecast of the two lakes to prediction of spatio-temporal distribution pattern of sediment deposition; 3) indicative assessment of the impact of the evolution of the two lakes on flood/dry regulation function, including indicators characterizing the flood/dry regulation function of the lakes and their responses to different scouring and silting scenarios in the future.

本研究分析了1960-2008 年鄱阳湖流域的气候和水文变化特征,用水量和能量平衡关系解释和印证了这些特征,并由此揭示了鄱阳湖流域水文变化特征的成因及干旱和洪涝发生的规律。得到以下主要结论:1) 正常或偏湿年份鄱阳湖流域6 月份容纳水量能力已达到饱和,若6-7 月降水量超出正常年份,则流域超饱和,洪涝发生。长江中上游降水量7 月份的异常偏多会对鄱阳湖流域的洪涝起触发和强化作用。2) 鄱阳湖流域7-10 月蒸发量大于降水量,特别是7-8 月蒸发量大于降水量的一倍以上,所以若4-6 月流域降水量少于平均年同期量的20%以上,则累积效应使秋旱发生。当初冬(11 月) 降水偏少时,秋旱可持续到来年的初春,形成严重的春旱。长江中上游降水量对鄱阳湖流域的春旱没有直接影响,但7-8 月降水量偏少时则对秋旱起重要的强化作用。3) 长江对鄱阳湖流域的水文过程和旱涝的发生、发展的影响主要在7-8 月的“长江与鄱阳湖耦合作用”时期和9-10月的“弱长江作用”期。

Observational data from 1960-2008 were analyzed to obtain the mean annual climate and hydrological variations in the Poyang Lake basin, China. These variations were explained by the surface water and energy budgets, and the characteristics of these variations and the budgets were further used to deduce the rhythms of flood and drought developments in the lake basin. Some conclusions can be drawn as follows. (1) The precipitation in the lake basin increases at a large rate from January to June, reaching the annual maximum in late June. Amplifying monthly precipitation, particularly from April to June, coupled with weak surface evaporation and transpiration (ET), saturates the soils and produces a large amount of surface runoff which raises the lake level. In July, rainfall decreases sharply with clear sky and high ET, which reduces surface runoff and reverses the hydrological processes developed in the first half of the year. These drying processes continue through October, making the basin dry again. (2) When June and July have above average monthly precipitation the lake basin becomes supersaturated, and floods develop. In such conditions, if July rainfall in the middle and upper reaches of the Yangtze River basin is above average, the Yangtze River blocking (or reversed flow) effect can trigger, intensify, and prolong Poyang Lake floods. Thus, Poyang Lake floods generally occur in July and August. (3) Because the lake basin is drying after July with strong ET, if there is below average rainfall in July and the months afterwards, ET would be greater than rainfall, causing drying. Drought could occur in fall. This fall drought can persist through the winter and into the following spring and result in severe spring drought in the lake basin. Thus, the droughts occur in the fall and spring months in the lake basin. (4) The Yangtze River effects on the floods and droughts in the lake basin are most significant during the "river-lake coupling period" from July to August. Strong effects can lead to floods in the lake basin. Lack of river effects would help lower the lake level and dry the basin, leading to drought in fall.