基于HYDRUS对稻田不同阶段土壤水分的模拟与分析

在稻田淹水到排水干田的过程中,稻田的土壤水分由饱和态转为非饱和态,这一过程中稻田土壤水分运移规律的变化以及水量各平衡要素的转化对稻田水分管理以及减缓农业面源污染等方面具有实际意义.为探寻稻田不同阶段土壤水分状况下的差异性,基于重庆丘陵区紫色土常规轮作水稻土壤水分的连续监测数据,利用HYDRUS-1D模型对稻田淹水、排水落干和收获后3个不同干湿阶段(阶段Ⅰ,Ⅱ,Ⅲ)的土壤水力参数和土壤含水量开展验证模拟分析.研究表明:(1) 根据R²与RMSE的误差分析结果,HYDRUS可以实现对不同阶段稻田土壤水分变化的有效模拟.(2) 根据土壤水量平衡分析,阶段Ⅰ的稻田土壤水分以水分补充的形式为主;阶段Ⅱ和Ⅲ的土壤水分以水分损失为主,底层渗漏量分别占总水分损失量的52%和95%.(3)根据HYDRUS的模拟结果,降雨直接影响土壤上下边界流的变化;阶段Ⅱ的实际作物蒸腾量和实际地表蒸发量低于阶段Ⅰ的,阶段Ⅲ稻田土壤的地表实际蒸发量与日照时数的关系更密切.

Simulation and analysis of soil water in different stages paddy field based on HYDRUS

The process of rice paddies from flooded to drainage dry fields, the soil moisture status of paddy soil to achieve the transformation from saturation to unsaturated state. During this process, the soil moisture transport law and the transformation of the water balance factors involving soil moisture are different. In order to explore the differences of soil moisture status in different stages of rice field, based on the continuous monitoring data of soil moisture of conventional rotation rice in purple soil in Chongqing hilly area. The HYDRUS-1D model was used to verify and simulate the soil hydraulic parameters and soil content in three different dry and wet stages(stage Ⅰ, Ⅱ, Ⅲ)of rice flooding, drainage drying and post-harvest. The results indicated that: (1) according to the error analysis from R² and RMSE results, pressure heads and vertical fluxes simulated using HYDRUS-1D matched measured data well. The HYDRUS-1D can be used to simulate the change of soil water content in the paddy field; (2) According to the analysis of soil water balance, the rice soil water in stage Ⅰ was mainly in the form of water supplement. The soil water loss in stage Ⅱ and Ⅲ is mainly water loss, and water leaching(approximately 52% and 95% in stage II and stage III, respectively)was the main path of water loss from the flood to dryland rice filed; (3) According to the simulation results of HYDRUS, the rainfall directly affects the change of upper and lower boundary flow of soil. Following the simulation results, the sunshine hours bring obvious diurnal variation rule for evapotranspiration fluxes. The actual crop transpiration and surface evaporation of stage II were lower than those of stage Ⅰ, while the actual surface evaporation of stage III was more closely related to the sunshine hours.