用水平土柱和修正的Green-Ampt模型确定土壤的入渗性能

Algorithm method for soil infiltrability determination with modified Green-Ampt model

土壤入渗能力和降雨产流过程及地下水密切相关。土壤入渗过程决定了灌溉/降雨过程中水分进入土壤的过程,影响了化肥、农药及其他污染物随水分迁移过程以及坡面水文与土壤侵蚀过程等。该研究根据水流在水平土柱中运动的能量要求以及实际测量得到的土壤水分分布,对Green-Ampt模型中含水率分布呈活塞运动推进(即湿润锋内部土壤水分为恒定值)的假定进行了修正。采用更符合实际的呈线性分布的土壤水分分布模型,基于水量平衡和土壤水动力学原理,提出了对应的土壤入渗性能的计算模型。给出了利用修正模型估计土壤入渗性能的方法,计算模型以及计算过程。结果表明,利用修正模型估算得到的土壤入渗性能回归的入渗水量与实际供水量的相对误差为0.66%,说明该修正模型和计算方法具有很高的精度。该文提出的修正模型很好地描述了水分在土壤中的分布,较Green-Ampt入渗模型中的活塞模型更符合土壤水动力学中关于土壤水分运动的分析。将该修正模型与水平土柱试验结合,可以大大地提高土壤入渗性能计算的精度,为以后的土壤水分运动,地表产流计算以及土壤侵蚀等方面的研究提供非常有效的工具。

The soil infiltrability has a close relationship with overland flow and groundwater, determining the fraction of the irrigation or rain water entering the soil, the transportation of chemicals such as fertilizers, herbicides/pesticides as well as other pollutants, and, thus, affecting the amount of runoff responsible for subsequent soil erosion. Based on the energy principle of water movement in saturated/unsaturated soils and the measured soil water distribution in horizontal soil column,modifications were made to the piston assumption of the soil water distribution in the Green-Ampt infiltration model. The soil water distribution was described by a more realistic linear distribution model. Based on the water/mass balance and the soil water dynamics, a modified mathematic model for soil infiltrability estimation was advanced. The measurement method, algorithm models and procedures were given for estimating soil infiltrability with measured data from horizontal soil column. Comparisons of the cumulative infiltration computed from the estimated infiltrability with the modified method and the total supplied water indicated that the relative error was 0.66%, which demonstrated a very high accuracy of the model and the computational method. The modified model can describe the distribution of the soil water very well which is more suitable to the analyzations in the soil water dynamics than the piston assumption in the Green-Ampt infiltration model. The accuracy can be greatly improved by applying the modified model to the horizontal soil column experiment. This can supply a very useful tool to the relative studies such as the soil water movement analysis, overland flow estimation and soil erosion analysis.