山坡表层关键带结构与水文连通性研究进展

山丘区是洪水的"策源地"，山丘区坡地、沟谷及间歇性河道为洪水的形成提供了通道，同时也是水文连通时空变化最为强烈的地带。然而，对流域表层关键带结构特征及其水文连通机制等的认识尚存不足，限制了产汇流理论及模型方法的发展和应用。通过对比国内外山坡水文实验，发现山坡物理结构连通性控制并深刻影响着水流的连通过程，现有水文连通实验侧重孔隙等微观尺度的规律研究，与水文模型理论存在尺度上的巨大偏差。为此，提出水文连通性应侧重揭示水流在山坡地表、地下的宏观表象通道及分布特征，探索径流连通的动力学机制，即山坡水文连通性研究重在剖析其结构特征的水文累积效应，应保持关键带结构特征合理概化与产汇流理论适度复杂之间的平衡。

Understanding of critical zone structures and hydrological connectivity: a review

Upstream areas are the major flood contributing areas in humid regions. Upstream hillslopes,valleys and ephemeral channels provide quick pathways for flows during flood events. These pathways generate flows seasonally and only after a rainfall event,i.e.,the hydrological connectivity is ephemeral. Thus the dynamics of drainage networks such as expansion/contraction,and connection/disconnection,may offer important clues to understanding the patterns and processes of runoff generation. However,the mechanism of what controls the hydrological connectivity and how it connects the hillslope,valley and channels is yet to be understood. Extensive field studies in diverse catchments around the world continue to characterize and catalogue the enormous heterogeneity of hillslope structures and complexity of rainfall runoff processes in multiple watersheds,and at different scales. But,these field findings seem to be meaningless for the modeler,as they usually fail to incorporated the experimentalist's knowledge into their models. There is plenty of knowledge gap in the fundamentals with regard to how catchment are composed,organized and connected through hillslopes,valleys and channels,and how catchment storage affects rainfall-runoff responses. In this study,through comparisons of hillslope experiments,we find that process based connectivity is deeply affected by hillslope soil depth,bedrock terrain and drainage network structures. This review also showed that present research works are focusing on micro-scale mechanism (e.g.,soil pores and flow),and there is a gap between the hydrological connectivity experiments and the modelers. We suggest that experimentalists should find a macroscale pathway hidden in the critical zone that is the pivot of the runoff generation and shapes the flow hydrodynamics in the entire catchment. That is to say hydrological connectivity of hillslopes,valleys and ephemeral channels should focus on the cumulative effects of hillslope processes instead of individual soil pore processes. Finally,there should be a balance between conceptualizing of complex hillslope structures and moderate depiction of runoff generation.