洪水脉冲驱动下的河流-洪泛系统内潜流交换机理研究

Hyporheic zone plays a critical role in maintaining the ecological health of rivers on a full reach scale. Natural or anthropogenic flood pulse can cause profound influences on the hyporheic flow regime and ecological structure within the river-floodplain system. A deep understanding of the hyporheic exchange of river- floodplain system would be conducive to quantitative assessment of the ecological impacts that caused by the flood pulse, and also it is helpful to improve the overall assessment of the ecological health of the river and its coordination function . In this study, a group of field tests, comprehensive theoretical study and numerical analysis method are combined to study the flood pulse effect on the mechanism of hyporheic exchange and water environment. Based on detailed experimental data, we will quantify the relationship between dynamic characteristics of hyporheic exchanges and the quantitative parameters of the flood pulse on variable temporal and spatial scales. In addition, based on the thermal tracer technique, this project will reveal multidimensional exchange mechanisms and temporal distribution of water and heat under flood process, and also to quantify the impact of flood pulse weights on hyporheic exchange amount. Finally, we will establish the conceptual model of the hyporheic zone, use the state-of-art numerical simulation tools to further reveal the mechanism of each exchange characteristics responding to the flood pulse. Based on this study, some novel knowledge of hyporheic exchange under flood pulse is expected, leading a prosperous theory and technique development of the interaction between surface water and groundwater.

潜流带对河流生态健康维持起着十分重要的调控作用。受人类活动或季节性洪水所引发的洪水脉冲效应形成了对河流-洪泛系统潜流区水流环境和生境结构的强烈冲击。研究河流-洪泛系统潜流区水流交换机理有助于定量评估洪水脉冲对河床区生态环境影响效应，完善对河流生态健康及其协调功能的整体性评价。本课题通过现场试验、理论研究和数值分析综合方法，开展洪水脉冲效应对潜流带交换机理及水环境评估研究，基于详实的试验数据，探究潜流交换空间动态特征与刻画洪水脉冲特征参数间的定量关系；基于热示踪技术揭示河流-洪泛系统内潜流区多维水流交换机制及水热时空分布规律，量化洪水脉冲影响权重；建立潜流交换概念模型，采用数值模拟手段进一步揭示潜流交换特征对各影响要素的响应机制。本课题将在复杂水流条件下潜流交换机理研究方面有所突破，研究成果可进一步完善和发展潜流带理论分析方法及试验研究技术。

潜流带对河流生态健康维持起着十分重要的调控作用。受人类活动或季节性洪水所引发的洪水脉冲效应形成了对河流-洪泛系统潜流区水流环境和生境结构的强烈冲击。研究河流-洪泛系统潜流区水流交换机理有助于定量评估洪水脉冲对河床区生态环境影响效应，完善对河流生态健康及其协调功能的整体性评价。本课题通过现场试验、理论研究和数值分析综合方法，开展洪水脉冲效应对潜流带交换机理及水环境评估研究，研究工作主要从河流-洪泛系统两个水力交互界面展开：在主槽-洪泛区界面上，研究揭示过流量65%以上的水量通过洪泛滩地传输，并且主槽和滩地之间存在极为频繁的水力交换；在水-沙界面上，洪水脉冲过程会有效增进潜流交换，交换量随地表流速的增大而增大，呈现幂函数关系，停留时间则与地表雷洛数呈现反幂函数；此外，河流床面形态是影响潜流交换的重要驱动力，即便是相似的地表水动力条件下，因床面形态引发的潜流交换可能会显著不一样，因此，本次研究给出了包含洪水作用与床面形态在内的5参数评估模型，该模型能够对河流系统潜流交换特征量进行快速预测。