基于Hydrus-1D模型构建代理模型的下渗计算应用

Application of surrogate model in infiltration calculation based on hydrus 1D model

Hydrus-1D模型在计算下渗过程中存在模型参数较难确定、计算时间长且不收敛等问题。应用Hydrus-1D模型计算下渗曲线,尝试在此基础上根据代理模型构建原理对输入与输出数据进行重构,建立表达输入、输出间函数关系的代理模型,从而提高模型的效率和适用性,并应用代理模型在稳定降雨和变雨强条件下分别进行验证。结果表明,在稳定降雨条件下,代理模型计算的下渗率过程线与hydrus-1D计算的下渗率过程线较为吻合,而在实际的变雨强条件下,当降雨强度大于土壤下渗能力时,代理模型和hydrus-1D模型吻合,当场次降水过程中降水量突然变小,且降水强度小于土壤实际下渗能力时,代理模型并不能考虑土壤疏干的情况,计算土壤下渗率会有精度的损失。进一步对代理模型进行改进,考虑壤中流对土壤水分的影响后,代理模型能模拟出当降雨强度再次大于土壤实际下渗能力时,土壤下渗率会出现突变的情况。

In the process of calculating infiltration,HYDRUS-1D model has some problems such as difficult to determine the model parameters,longer calculation time and non-convergence.The HYDRUS-1D model is used to calculate the infiltration curve.On this basis,the input and output data are reconstructed according to the construction principle of the proxy(or surrogate)model,and the proxy model expressing the functional relationship between input and output is established,so as to improve the efficiency and applicability of the model.The proxy model is verified under the conditions of stable rainfall and variable rainfall intensity.The results show that under the condition of stable rainfall,the infiltration rate hydrograph calculated by the proxy model is consistent with the hydrograph calculated by HYDRUS-1D.Under the condition of actual variable rainfall intensity,when the rainfall intensity is greater than the soil infiltration capacity,the proxy model and HYDRUS-1D model coincide.When the precipitation suddenly decreases in the process of same precipitation and the precipitation intensity is less than the actual soil infiltration capacity,The proxy model cannot consider the soil draining condition,and there will be a loss of accuracy in calculating the soil infiltration rate.The proxy model is further improved.After considering the influence of soil flow on soil moisture,the proxy model can simulate the abrupt change of soil infiltration rate when the rainfall intensity is greater again than the actual infiltration capacity of soil.