基于野外观测实验的中国东部湿润区降雨入渗模拟分析——以宁波画龙溪流域为例

Simulation analysis of rainfall-infiltration in humid regions of the eastern China based on field observations:A case study of the Hualong River Basin,Ningbo City

本文以中国东部湿润区典型小流域浙江宁波画龙溪为例,将野外原位定点观测与模型模拟分析相结合,建立了HYDRUS-1D土壤水模拟模型,选取2016年9月29日、2016年10月7日典型降雨事件分别对模型进行率定和验证,并对2016―2020年不同降雨强度下不同土地利用类型的场次土壤水分入渗开展了观测与模拟,以揭示中国东部湿润区不同土地利用类型下的降雨-入渗规律。结果表明:(1)从土壤水分变化过程模拟来看,HYDRUS-1D模型模拟土壤水分动态变化特征具有较高的精度,90%模拟结果的纳什效率系数达到0.80以上。(2)在同等降雨强度下,4种土地利用类型土壤下渗量从大到小依次为农田、杨梅林、坡耕地、竹林。下渗率受降雨量及降雨强度影响较大,不同土地利用下土壤下渗量随着降雨强度增强而显著增加。(3)土壤下渗量同时也受到降雨历时与前期降雨情况深刻影响。当降雨强度从小雨逐级增加到大暴雨,各土地利用类型下渗量略微增加,但增加量均小于5%。对于历时短、强度高的极端降雨事件,降雨强度超过了下渗强度,形成超渗产流,将出现降雨量大但下渗量反而小的现象。本研究成果可为中国东部湿润区农业生产、三水转化规律等提供理论参考。

Soil moisture plays a significant role in water infiltration,evapotranspiration,and solute transport in the unsaturated zone,there are remarkable differences in rainfall-infiltration characteristics within different rainfall intensities and different land use types,which is crucial for plant growth and the dynamics of ecosys-tem.In this article,taking the Hualong River,Ningbo City,Zhejiang Province,as an example,combining field in-situ fixed-point observation and model simulation analysis,a soil moisture simulation model HYDRUS-1D was established.And the model was calibrated and verified by using the typical rainfall events on September 29,2016 and October 7,2016.Moreover,a soil water infiltration simulation of different land use types under different rainfall intensities was carried out based on HYDRUS-1D model from 2016 to 2020,to reveal the law of rainfall-infiltration under different land use types in the eastern humid region of China.Results showing that:1)According to the simulation of soil moisture change process,the HYDRUS-1D model has high accuracy in simulating the dynamic change characteristics of soil moisture,and the Nash efficiency coefficient of 90%sim-ulation results is over 0.8;2)Under the same rainfall intensity,the soil infiltration amounts of the four land use types were farmland,waxberry forest,sloping farmland,and bamboo forest in descending order.The infiltra-tion rate was greatly affected by rainfall and rainfall intensity,and the soil infiltration amount increased signi-ficantly with the increase of rainfall intensity under different land uses.3)Soil infiltration is also profoundly af-fected by rainfall duration and previous rainfall.When the rainfall intensity increases one level furtherly,the in-crease in infiltration of each land use type was less than 5%,and maintained a slight increase.And when ex-treme rainfall events occur,the rainfall intensity exceeds the infiltration intensity,resulting the infiltration ex-cess runoff,causing the phenomenon of large rainfall but small infiltration.The research results can provide theoretical reference for agricultural production,three-water transformation law and ecological protection re-search in the humid region of eastern China.