华北典型山区坡地径流的退水过程研究

Discharge recession from runoff plots in representative mountain area in North China

通过位于北京市怀柔区东台沟的华北山区典型坡面径流场内人工模拟降雨实验,分别讨论了地表径流、壤中流和基岩风化带出流共3层的退水特征,三者比较结果表明,壤中流最早开始退水,其退水历时最长,流量最小;地表径流的退水一般受降雨和地形地貌的影响,雨停后迅速消退;基岩风化带出流通常在地表径流退水的后半段开始.影响因子分析表明,降雨历时与地表径流的退水流量呈幂函数变化趋势;雨强与地表径流的退水流量呈对数变化趋势;雨强与壤中流和基岩风化带出流的退水流量之和呈线性变化趋势.雨强还影响退水流量在总径流量中的分配比例.地表径流、壤中流和基岩风化带出流的退水流量分别占总流量的7.8%、1.7%和5.9%.当雨强<1.5 mm/min时,随雨强增加地表径流退水量的比例呈直线增加趋势,雨强>2 mm/min时地表径流退水量所占比例反而下降.基岩风化带出流的退水流量所占比例呈幂函数逐渐下降的趋势,壤中流的比例一直较小.计算结果表明,该区退水常数可以分地表径流退水和壤中流--基岩风化带退水共2层,其值分别为0.75和0.94.这一结果为进一步研究坡面水文过程乃至流域的退水过程提供了参数.

Rainfall simulation on representative plots （5 m wide and 10 m long） in a mountainous area of North China was carried out to compare water discharge and recession characteristics by surface runoff, soil-layer flow and mantle rock flow. Results show that soil-layer flow recesses first with the longest duration and lowest discharge, surface runoff recession which is affected by rainfall and topography ceases with rainfall stop, and mantle rock flow recesses generally ensuing surface runoff recession. Duration and intensity of rainfall are dominant factors affecting discharge recession. The amount of surface runoff recession has a power trend to the increase of rainfall duration. Rainfall intensity and surface runoff recession present a logarithmic regression and rainfall intensity and summation of discharge recession from soil-layer and mantle rock show a linear relationship. Rainfall intensity also affects the proportion of recession discharge by surface runoff, soil-layer flow, and mantle rock flow to total discharge, which are 7.8%, 1.7% and 5.9%. With the increase of rainfall intensity, the proportion of recession by surface runoff increases linearly when the intensity is lower than 1.5 mm/min. However, the proportion of surface runoff recession to total discharge decreases to very low if the intensity is above 2 mm/min. The proportion of mantel rock recession has a power trend to decrease with the increase of intensity, and that of soil-layer recession is generally low. The result shows that the recession constant in this area should be divided into surface recession （0.75） and soil-layer and mantle rock recession （0.94）. These primary results will present parameters for the further research of recession on hydrological processes on slopes and catchment.