Quasi-analytical Solution Of Groundwater Depth And Its Application Under Periodic Precipitation And Evaporation

The movement and change of groundwater depth is very important in the study of groundwater,which can not only reflect the hydrological law of groundwater,but also directly affect the production and life of human beings.Under natural conditions,shallow groundwater mainly carries on precipitation recharge and evaporation discharge.At present,there are few studies on groundwater depth under periodic climate conditions,but the reality shows that describing the influence of periodic precipitation and evaporation on groundwater depth can better understand the law of groundwater movement.In this paper,the groundwater depth movement model under periodic precipitation and evaporation is established and its approximate solution is obtained.By analyzing the approximate solution,the influence of periodic characteristics of precipitation and evaporation on the groundwater depth is discussed.Chapter 1 is the introduction,which mainly introduces the research background and previous research methods of groundwater dynamic change based on literature.The importance of the influence of precipitation and evaporation on the dynamic change of groundwater depth and the research advances at home and abroad are analyzed.In chapter 2,the concept model of groundwater dynamic change is given firstly,and then the mathematical model is built and simplified under certain conditions.The approximate analytical solution of the mathematical model in the case of the geological environment and vegetation parameters for n=1 to 3.When n is an integer,Fourier series is used to expand the differential equation to obtain a periodic solution.When n is an arbitrary real number,Newton's iteration method is used to solve the equation to obtain an approximate solution state.The results are compared with those of other numerical methods.Chapter 3 analyzes the solution of groundwater depth of amplitude,phase and the relationship between precipitation and evaporation by using the approximate analytical solution.Figures and expressions are used to show how periodic precipitation and evaporation drive changes in groundwater depth.In addition,this chapter also analyzes the influence of geological environment and vegetation parameters on the dynamic change of groundwater depth.Chapter 4 provides an actual case of Wushen county,the Inner Mongolia Autonomo by fitting verification and application.All the conclusions in this paper have been tested by strict mathematical derivation and practical data,which provide a new method for describing and studying the depth of shallow groundwater.