黄土区空闲坡耕地地表径流产沙近似解析模型

准确地预测农田地表径流是实现农业面源污染控制的基础,根据降雨和地表径流的运动特征,耦合Green-Ampt模型累积入渗量显函数、运动波模型和稳态的产沙模型,建立了降雨条件下的坡面产流产沙近似解析模型。该模型通过线性表示入渗率和水深之间的关系近似求解了运动波方程,通过设置30~90 mm/h的5种不同雨强的模拟降雨试验,推求模型参数并验证模型精度,并对模型参数进行敏感性分析。结果表明:(1)径流和泥沙的模型计算值与实测值吻合较好,且模型更适合于模拟60 mm/h雨强下的产流产沙过程,曼宁糙率系数均分布在0.00026~0.00029 min/cm^1/3,入渗率参数c与雨强的关系可以用指数函数c=9×10^-4p^-0.644对其进行描述,产沙模型中的参数a和b分别分布于0.13~0.15和0.10~0.12,由于泥沙运动的偶然性因素,产沙过程的模型模拟精度低于径流过程。(2)当c取值为0~0.05时,Dif值变化较小,即地表径流对入渗率参数c敏感性较弱;径流产沙过程中,Dif值随参数a和b的变化均有不同程度的波动。总体来看,径流产沙率对径流冲刷系数a比雨滴侵蚀系数b更为敏感。

Approximate Semi-analytical Model for Surface Runoff and Sediment Yield of Idle Sloping Farmland in Loess Area

Accurately predicting farmland surface runoff is the basis of controlling agricultural non-point source pollution. According to the motion characteristics of rainfall and surface runoff, coupled with the Green-Ampt model, the apparent function of cumulative infiltration, the Kinematic wave model and the steady-state sediment yield model, an approximate semi-analytical model for slope runoff and sediment yield under rainfall conditions was established. The model approximated the Kinematic wave equation through linear expression of the relationship between the infiltration rate and the water depth. By setting the simulated rainfall test under five different rain intensities between 30~90 mm/h, the model parameters were derived and the model accuracy was verified, and the sensitivity of the model parameters were analyzed. The results showed that: (1) The calculated value of runoff and sediment model was in good agreement with the measured value, and the model was more suitable for simulating the runoff and sediment yield process under 60 mm/h rainfall intensity, and the Manning''s roughness coefficient distributed between 0.000 26~0.000 29 min/cm^1/3, and the relationship between the infiltration rate parameter c and the rain intensities could be described by an exponential function c=9×10^-4p^-0.644. The parameters a and b in the sediment yield model distributed between 0.13~0.15 and 0.10~0.12, respectively. Due to the accidental factors of sediment yield, the model simulation accuracy of the sediment yield process was lower than that of the runoff process. When the value of c was 0~0.05, the value of Dif changed little, it indicated that the soil surface runoff was not sensitive to c. In the process of runoff sediment yield, the value of Dif varied with the change of parameters a and b. Overall, runoff sediment yield was more sensitive to the runoff erosion coefficient parameter a than the parameter raindrop erosion coefficient b.