侵蚀能量流视角下的小流域系统径流输沙尺度效应

Watershed erosion and sediment yield is a nonequilibrium complex process coupling multidimensional distributed parameters, the condition of runoff and sediment discharge is highly dependent on the spatial scale. It is of vital significance in promoting the research on scale issues in watershed erosion to understand the spatio-temporal variations of the interrelationships between erosional system and environmental factors, especially within a context of energy-based perspectives and dynamic system strategies. Aiming at the lacking of sufficient attention towards scale continuity and cross-scale interactions, as well as continuous spatial variation of runoff and eroded sediments at multi-scales in studies on scale issues in watershed erosion, a typical agricultural watershed in the Loess Hilly Gully Region is selected to investigate the spatial scale dependency of runoff and sediment discharge within small basin system. Multi-scale continuities will be established through the organization of continuous observational systems across various spatial scale series. Based on the pattern analysis of runoff and erosive energy flow, multi-scale continuous effects of runoff erosion will be studied within multiple channel systems. It is anticipated that the intra- and inter-scale transfer and conversion of runoff erosive energy will be explicated within small watershed system. Therefore, the intrinsic connections between flood runoff and sediment process and erosive energy flow will be illuminated at different spatial scales to reveal the sediment effects driven by runoff erosive energy and the potential significance of erosive energy regulation in water and soil conservation. The study is expected to provide beneficial reference for the promotion of rational design, effective allocation, and optimal layout of anti-erosion measures, as well as the improvement of soil erosion control level at the watershed scale.

小流域侵蚀产沙是一个非平衡的复杂过程，径流输沙状态受空间尺度的高度制约。基于能量的观点，从动态系统的角度出发理解侵蚀系统与环境因子相互关系及其时空变异，对于深化流域侵蚀尺度问题的研究具有重要意义。针对流域侵蚀尺度问题研究中对空间尺度连续性信息及尺度间相互关系、多尺度径流与侵蚀泥沙连续空间变异的反映不足等问题，本研究以黄土高原丘陵沟壑区典型农业小流域为例，通过建立多尺度连续观测体系，基于多尺度洪水径流过程和侵蚀能量流的连续空间变异分析，解析多重沟道体系径流侵蚀的多尺度连续效应，以期明确径流侵蚀能量在流域系统不同尺度内和尺度间的传递、转化特征，解析不同空间尺度的洪水径流过程、输沙过程及其与相应侵蚀能量的内在联系，阐明径流侵蚀能量对泥沙输出的驱动作用，揭示流域系统侵蚀能量调控的潜在水土保持意义。研究有望为促进流域水土保持措施合理设计、有效配置与优化布局和提高流域水土流失治理水平提供有益借鉴。

针对流域侵蚀尺度问题研究中对空间尺度连续性信息及尺度间相互关系、多尺度径流与侵蚀泥沙连续空间变异的反映不足等问题，本研究以黄土高原丘陵沟壑区典型农业小流域为例，选取9个不同部位和控制面积的坡面径流小区及流域毛沟、支沟、干沟等不同尺度，系统研究了近自然状态下非治理流域不同空间尺度洪水径流格局及其的侵蚀输沙效应、定量解析了不同尺度侵蚀能量链的径流输沙空间动态及其能沙关系。研究发现，洪水径流过程的复杂性有随尺度增加而降低的趋势。输沙模数、径流含沙量的变异性及含沙水流的空间尺度效应均呈降低趋势。洪水径流总量相同的情况下，不同洪水径流格局之间转换造成水沙关系改变，由此引起的最大增沙效应随尺度和径流总量的增加呈减小趋势，最大增沙效应出现在全坡面尺度，最小增沙效应出现在支沟尺度。坡面系统主要泥沙变量随尺度增加均表现出增大的趋势，水沙关系多变；进入沟道体系，径流侵蚀链内泥沙输出过程的主要驱动因素趋于单一，高含沙水流含沙量、尺度内及尺度间水沙关系均表现出空间上的独立性（不变性）。基于能量观点和流量过程的不同侵蚀能量指标可反映径流侵蚀能量的累加效应及能量释放的瞬时作用效率，于构建能量-泥沙传递关系中具有较好的模拟效果。研究有望为促进流域水土保持措施合理设计、有效配置与优化布局和提高流域水土流失治理水平提供有益借鉴。