空气阻力影响下的分层土壤非稳定降雨入渗产流模型

摘要

During the period of rainfall or irrigation,the air in soils fails to fully escape,which is trapped in soils and causes air resistance that hinders soil water infiltration.Considering the impact of air resistance on the soil water infiltration process,the Green-Ampt model is modified.A modified Green-Ampt model (MGAM) is proposed for simulating infiltration into layered soil profile with consideration of air resistance under unsteady rainfall.In order to account for the effect of air resistance,the saturation coefficient (Sa),actual water content (θa),air bubbling pressure (hab) and water bubbling pressure (hwb) are introduced in the model.All parameters could be approximately determined by soil physical properties.To evaluate the performance of MGAM developed by the authors,one-dimensional infiltration-runoff experiments are performed in multi-layered soil columns during unsteady rainfall with air confined.Then soil cumulative infiltration,runoff rate and soil water content calculated by MGAM are compared with the observed data from the experiments,and the calculated results of the traditional Green-Ampt model (TGAM) without consideration of air resistance.The results indicate that soil cumulative infiltration,runoff rate and soil water content calculated by MGAM are all in better agreement with the observed than the existed models.The calculated soil water content and soil cumulative infiltration by TGAM are larger than the observed,and runoff rate is less than the observed.%降雨或灌溉期内,土壤内的空气很难及时全部排出.禁锢在土壤中的空气产生的压力阻碍了土壤水分入渗.针对空气阻力对土壤入渗过程的影响,对Green-Ampt模型进行了改进,提出了非稳定降雨条件下考虑空气阻力作用的分层土壤降雨入渗产流模型(MGAM).模型中,引入了饱和度系数(Sa)量化入渗水分剖面滞留空气影响下的实际导水系数和实际含水量,引入进水值(hwb)和进气值(hab)量化湿润锋处实际负压水头,并提出由土壤物理性质估算饱和度系数(Sa)、进水值(hwb)和进气值(hab)的参数化方案.为了验证模型适用性,采用MGAM模型模拟分析了室内开展的空气限制条件下的分层土壤非稳定降雨一维入渗产流试验观测成果,包括土壤水分分布特征、土壤累计入渗量和径流强度,并将模型模拟值与试验观测值,以及传统不考虑空气阻力TGAM模型(Traditional Green-Ampt Model)模拟值进行了对比分析,结果表明MGAM模型模拟的土壤累计入渗量、土壤含水量和径流强度均与实测结果吻合良好,而TGAM模型模拟土壤累计入渗量、土壤含水量均大于实测值,而径流强度小于实测值.