| As one of the main links of the water cycle,soil water movement is an important link connecting the four water cycles(atmospheric water,surface water,groundwater and soil water),and is the main source of crop growth.In the shallow groundwater area,soil water and groundwater exchange frequently.The Huaibei Plain of Anhui Province is located in the eastern part of China.It is a typical area of the north-south climate transition zone,with frequent droughts,floods and water logging.Therefore,the study of water movement rule and the conversion relationship with groundwater is of great significance for the transformation of field water and the formulation of reasonable irrigation plans in Huaibei plain of Anhui Province.The research was carried out at the Wudaogou Hydrology and Water Resources Experimental Station in Anhui Province.The data of soil water,groundwater,meteorology and crops were collected through on-site investigation.Based on this,relevant experiments were carried out to study the annual and inter-annual variation characteristics of soil moisture.The effects of rainfall,crops and groundwater level changes on soil moisture in different soil layers during different growing seasons were analyzed,and the regression model of groundwater level and soil moisture in each soil layer was established and verified.The Hydrus-1D model numerically simulates the soil moisture in the summer maize growing season under the groundwater level control experiment,and the exchange amount of soil water and groundwater is obtained.The research results can provide a theoretical reference for agricultural public opinion forecasting and the development of reasonable irrigation systems.The main research results are as follows:First of all,by analyzing the variation characteristics of the average soil moisture content of each soil layer of 0-0.1m,0.1-0.2m,0.2-0.3m,0.3-0.4m,0.4-0.5m,0.5-0.6m,0.6-0.8m,0.8-1.0m and 0-0.1m in 1992-2018 during the annual and inter-annual period,which showed that the most wet and dry occurrence of soil moisture in the year was March and May-June respectively,and the soil moisture content of each soil layer showed a gradual upward trend in inter-annual variation.Secondly,the characteristics of soil moisture in different profiles of different crop growth seasons(winter wheat and summer maize)from 1992 to 2018 were analyzed.The soil moisture of each soil layer in crop growing season showed different effects by crop,rainfall and evaporation.The average soil water content of the soil layers in the summer maize growing season experienced two stages of smooth and rising,and the soil moisture content of winter wheat land experienced two stages of stable and rapid decline.The average water content of 0.3-0.4m and 0.4-0.5m soil layers in winter wheat and summer maize growing season is higher than that in each soil layer,which indicates that the water holding capacity of this layer is good,especially in the drought period,this layer plays an important role in crop growth.Then,the effects of different rainfall and rainfall on soil moisture are different.The depths of rain,moderate rain,heavy rain,rainstorm on soil moisture are 0.35 m,0.35 m,0.45 m and 1.0m,respectively.Compared with crop land,crop land has a greater use of soil moisture.By analyzing the effects of groundwater level on soil moisture in summer maize and winter wheat growing seasons from 1992 to 2014,a regression model between the two was established,and the regression model was validated in 2016,2017 and 2018.The groundwater level and soil moisture content were linear.The deeper the soil,the better the correlation.Finally,the Hydrus-1D model can accurately simulate soil moisture changes.From the simulation results of the Hydrus-1D model,the exchange of soil water and groundwater is frequent.The storage value of soil water in the whole growth period of summer maize is-52.60 mm,and the cumulative recharge of groundwater to soil water is 295.08 mm. |
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