河湖淡水是社会经济发展的重要战略资源。国际上众多大河、大湖都具有洪泛特性而发育着面积巨大的洪泛区域。河湖洪泛区是陆地和水体之间的过渡带，其在河湖水体的水文和物质循环与平衡中起着关键的作用。已有研究显示，洪泛区水文过程通常呈现迟滞非线性特性，并对洪泛区的补排关系和水量调蓄机制产生重要影响。针对相关研究的不足与空白，本项目以鄱阳湖典型洪泛区为核心实验区，采用现场多要素高频观测和具有物理机制的数学模型为主要手段，重点研究湖泊典型洪泛区水文补排关系、洪泛区水文迟滞的湿地植物作用机理及洪泛区水量调蓄在湖泊水文平衡中的作用，注重解决洪泛区地下含水层径流滞留时间和排泄通量的识别和计算以及根系-土壤系统水文特性与植物蒸腾关系等关键科学问题。本项研究可望在洪泛区水量调蓄机制及其在湖泊水平衡中的关键作用等方面产出创新性成果，丰富洪泛平原水文学理论，并为应对全球变化，保障区域水资源安全提供科学支撑。

Freshwater rivers and lakes are important resources for social-economic development. Many large rivers and lakes in the world possess inundation characteristics and large area of floodplains is developed around them. The floodplain is a transition area between the aquatic and the terrestrial regions, and acts as a critical role in hydrological and mass balance of the surface water bodies. A number of existing studies showed that hydrological hysteresis was present in the hydrology of floodplain, and this non-linear behavior had significant effects on the recharge-discharge relation of the floodplain and its water storage regulation mechanism. Based on the research gaps of a complete literature review, exemplified in the typical floodplain of Poyang Lake, this proposal performs a thorough research on recharge-discharge relation, vegetation-induced hydrological hysteresis, and the function role of the floodplain in the overall hydrological balance of the lake. In-situ high frequency observations are conducted and physics-based mathematical models are used as primary research tools. In particular, this proposal focuses on a number of fundamental questions including the flow path and residence time of water in shallow aquifers, and the hysteretic characteristics of the root-soil system and the correlation with vegetation transpiration during drying and wetting cycles. The outcomes of this research are expected to provide new insights into the regulating mechanism of the floodplain in lake hydrological balance, and hence to enrich the floodplain hydrology theory. Scientific support may also be provided from this research for sustainable development and safety assurance of water resources under a rapid global change.