基于HYDRUS-2D的雨水集聚深层入渗系统土壤水分运移模拟

为了解雨水集聚深层入渗(RWCI)系统土壤水分的入渗规律,设置不同灌水量(10 L、21 L和36 L)和RWCI设计坑深(40 cm和60 cm)的室内土箱试验,观测不同灌水量与不同水头变化情况土壤含水率变化和土壤湿润锋在径向和垂直方向上运移过程,依据非饱和土壤水动力学理论,建立HYDRUS-2D变水头边界条件土壤水分二维入渗模型。通过与实测数据对比,结果表明模型模拟值和实测值具有较好一致性:垂向湿润锋相对均方差(R_E)、平均绝对误差(MAE)和纳什系数(NE)分别为0.019、0.011 cm和0.994,径向湿润锋R_E、MAE和NE分别为0.018、0.851 cm和0.977,土壤含水率R_E、MAE和NE分别为0.188、0.016 cm~3·cm~(-3)和0.916。相比于设计深度为40 cm的RWCI系统, 60 cm RWCI系统在不同灌水量下能够更有效地增加果树根系分布层的土壤含水率,增加土壤水分入渗深度;相同灌水量下RWCI系统设计深度的径向湿润锋分布间无明显差异,而垂直方向的分布具有明显差异;RWCI系统在相同的设计深度下,随着灌水量增大湿润锋在垂向与径向的运移距离差异逐渐增大。

Numerical simulation of soil water infiltration under rainwater collection and infiltration systems based on HYDRUS-2D

To understand the accumulation and infiltration of soil water in the rainwater collection and infiltration (RWCI) system, indoor soil tank tests with different irrigation amounts (10 L, 21 L, and 36 L) and RWCI design pit depths (40 cm and 60 cm) were conducted. The change of soil moisture content and the migration process of soil wetting front in radial and vertical directions under different water head changes under irrigation were observed. According to the theory of unsaturated soil hydrodynamics, the two\|dimensional infiltration model of soil moisture in the boundary condition of HYDRUS-2D variable head was established to analyze and verify the indoor tests. The results showed that the simulated and measured values of the model had good consistency, and the relative mean square error (R_E), mean absolute error (MAE) and Nash coefficient (NE) of the vertical were respectively 0.019,0.011 cm,0.994, and of the radial wetting front were respectively 0.018, 0.851 cm, 0.977, and of the soil moisture content were respectively 0.188, 0.016 cm³·cm^-3, 0.916. Compared with the RWCI system with a design depth of 40 cm, the RWCI system with a design depth of 60 cm increased the soil moisture content of the root distribution layer of fruit trees more effectively and increased the infiltration depth of soil moisture under different irrigation amounts. With the same irrigation amount, the RWCI system design depth had no significant difference in the radial wetting front distribution, but had a significant effect on the vertical direction distribution. Under the same design depth, the RWCI system significantly increased the wetting front in the vertical direction and the diameter as the irrigation amount being increased. The difference in migration distance gradually increased.