Variation And Analysis Of Soil Water Content Of Different Textures Under Rainfall Conditions

Soil is a geological resource that humans rely on for survival,and a channel for the exchange of water and energy between the surface and the ground.In order to study the movement and distribution of water in different texture soils,the variation of soil water content with rainfall,etc.,this paper analyzes the changes in soil water content of loam,sand and clay under different rainfall conditions,and establishes SWAP-PEST coupling The model is a qualitative analysis of the overall change trend from a macro perspective,and SPSS software is also used to specifically analyze the relationship between the soil moisture content of each layer and the response to rainfall.The main conclusions of this paper are as follows:(1)The distribution of water content of various soils throughout the year: From a vertical perspective,when the loam is not affected by groundwater,the soil water content at a depth of40 cm is the largest,followed by 100 cm,and finally 10cm;sandy soil basically follows the soil As the depth goes down,the moisture keeps increasing;the moisture content of each layer of clay does not differ much.The size of the soil moisture content is most affected by the geographical location and the external environment.In general,the clay has the largest moisture content,the strongest water holding capacity,and the sandy soil is the weakest.(2)Changes in soil moisture content throughout the year: The rainfall in summer and autumn is large,and the soil moisture in each layer varies greatly,which belongs to the period of severe fluctuations in soil moisture;there is less rainfall in winter and spring,which is the stable soil moisture.During the period,the whole year showed an upward trend and then a downward trend.The greater the initial soil moisture content,the smaller the degree of moisture fluctuation.Loam soil has only two adjacent layers with a certain hydraulic connection;there is almost no water exchange between the first layer of sand and the soil layer below,but the three layers below have close hydraulic connections;the four layers of clay soil have extremely close hydraulic connections throughout the year.The moisture change trend is similar.(3)There is no change in the soil moisture of the clay surface at the beginning of the rainfall.After the rainfall,the moisture content drops rapidly.On the contrary,the sandy soil has a faster response at the beginning,and the soil moisture drops slowly at the end.Rain generally only affects a depth of 100 cm.When a single rainfall is large,lasts a long time,and the initial soil moisture content is low,the soil moisture content fluctuates the most.The change of soil moisture content before and after rainfall presents a trend of rising first,then stabilizing and then falling,which can be roughly divided into three periods: rising period,stable period and falling period.(4)Under rainfall conditions,the variation amplitude of soil moisture content of each layer basically shows the characteristics of gradually decreasing with the increase of depth,and the hysteresis effect becomes more obvious with the increase of soil depth.Clay has the shortest lag time,and for the same kind of soil,the shorter the lag time for the change of deep soil water content when the rainfall is large.(5)Using the SWAP-PEST construct soil water movement model to simulate the daily changes of groundwater in each layer in Raoyang area in 2014,and to evaluate the simulation accuracy of the model.The results show that the model can simulate the state of soil moisture migration,and the simulation results are good,which reflects the applicability of the model.