不同下垫面红壤坡面产流的特征与过程模拟

Characteristics and Numerical Simulation of Runoff on Red Soil Slope with Different Coverings in Soil Surface

针对不同下垫面红壤坡面的产流特征及定量模拟问题,以江西省德安县水土保持科技园内的野外径流小区2016-2017年历次降雨径流观测试验为基础,对比分析了三种下垫面(裸地、百喜草植草覆盖、干草敷盖)条件下红壤坡面的产流特征;基于运动波理论和Green-Ampt入渗模型构建了红壤坡面产流数值模型,采用Preissmann差分法数值离散,通过试验数据进行率定验证;利用模型模拟不同下垫面状况、雨强下的坡面产流入渗过程。结果表明:(1)与裸地相比,干草敷盖、植草覆盖在不同降雨下均有显著的减流作用,平均减流率各为82.5%、87.9%;(2)利用实测数据验证本文模型,不同下垫面小区产流量模拟值与实测值的相对误差均在±10%以内,说明模型能反映不同降雨条件下不同下垫面红壤坡面的产流规律;(3)数值试验结果表明地表覆盖可增大入渗,延迟坡面产流,延迟效果随雨强增大而减弱;土壤初渗速率与雨强成正比,稳渗速率受雨强影响较小;雨强愈大,产流愈快进入相对稳定阶段,且稳定阶段的单宽流量愈大。研究可为红壤坡地水土流失定量评估和治理提供理论依据。

To understand the characteristics and quantitatively simulate the runoff on red soil slope with different coverings,the precipitation-runoff data on red soil slopes with three coverings(bare land,planting Paspalum notatum,mulching with Paspalum notatum)from2016 to 2017 are obtained by Jiangxi provincial Scientific and Technological Garden of Water and Soil Conservation.A numerical runoff model is constructed based on the kinematic wave equation and the Green-Ampt infiltration equation.The model uses the Preissmann difference method for spatial discretization,which is then verified by experimental data and further used to simulate the runoff and infiltration process of slope land with different coverings and rainfall intensity.The results show that:(1) Compared with the bare land,mulching with dried grass or planting Paspalum notatum significantly reduced the runoff amount under different rainfall conditions,and the average reduction rates were 82.5% and 87.9% respectively;(2) The relative errors between the simulated results from the proposed model and measured value of runoff were within ±10%,which showed that the model could reflect the runoff law of red soil slope with different coverings and different rainfall conditions;(3) The numerical tests showed that coverings in soil surface could increase the infiltration and delay the start of runoff,while the delay effect decreased with the increase in rainfall intensity.The initial infiltration rate is directly proportional to the rainfall intensity,while the steady infiltration rate is less affected by the rainfall intensity.The increase in rainfall intensity can shorten the runoff duration before the stable stage.This study can provide a theoretical basis for quantitative evaluation and control of soil erosion in red soil slopes.