大湖洪泛区水文迟滞与水量调蓄机制研究

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.

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。

以鄱阳湖洪泛区为核心实验区，采用现场多要素观测和具有物理机制的数学模型为主要手段，重点研究了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。重点解决了洪泛区地下含水层地下水动态过程和排泄通量的计算以及根系-土壤系统水文特性与植物蒸腾关系等关键科学问题。取得的创新性成果包括：湿地典型植物根系对湿地土壤水力特性有显著的影响，改进了根系-土壤系统垂向一维水分运用的模型参数，揭示了土壤水分补给地下水和蒸腾耗散的非线性迟滞现象及植物的作用机理；研发了大型湖泊洪泛区分布式地表-地下水耦合模型，模型植入了洪泛湖泊水文调蓄函数，有效模拟了洪泛湖泊的日尺度水文过程；定量揭示了洪泛区地下水与湖泊水体之间的水量交换机制，丰水年和枯水年的枯水季节（12月-2月）地下水排泄量占该时期湖泊蓄水量变化的20%-29%，个别枯水月份占比超过40%，阐明了在枯水期洪泛区地下水对湖泊水量的重要补给作用，弥补了以往研究的不足；产出的重要数据包括：现场原位观测和实验测试的鄱阳湖洪泛湿地典型植物根系数据，湿地土壤关键物理参数，根系-土壤系统水力参数，收集了长系列鄱阳湖水位观测数据及推算的湖泊面积和蓄水量数据，收集整理了鄱阳湖平原区地下水水位观测数据以及模型计算的地下水与湖泊日尺度水交换通量数据等；研发并构建了鄱阳湖湖泊-洪泛系统地表-地下水分布式水文模型，申报了发明专利，模型区域包括整个鄱阳湖平原区，面积24020平方km。本研究拓展了大型洪泛湖泊水文过程的认识，丰富了湖泊科学的理论，有助于更为客观评价气候变化和人类活动对湖泊水文平衡的影响，为应对未来变化，探求调控措施，减缓洪旱灾害，提供了有力的科学支撑。核心成果在国际主流刊物发表，部分成果支撑了关于2022年长江中游高温干旱的影响及对策建议一份，获得国家有关部门采纳，四名博士生受资助开展博士学位论文研究。