Study On The Effect Of E₀ Value On The Calculation Results Of Phreatic Evaporation In Bare Soil Area

In common phreatic evaporation experience formulas,the water surface evaporationintensity is usually used to replace the phreatic evaporation intensity at the zero groundwater depth?ie E₀?,which is not completely the truth and inevitably affects the reliability of phreatic evaporation calculation results.To this end,this paper carried out an experimental study on four homogeneous samples of coarse sand,fine sand,loam and sand through a self-made phreatic evaporation test device,in order to construct a quantitative relationship expression between E₀ value and water surface evaporation intensity,and then modify E₀.The results revealed that firstly under the same conditions,E₀ of different texture samples was not equal to water surface evaporation intensity,and the differences between the two were different in different seasons.The general trend was that E₀ of fine sand,sand and loam were higher than water surface evaporation intensity,while E₀ of coarse sand was lower than that.The higher the temperature and the stronger the solar radiation,the more obvious the difference.Secondly,the linear mathematical relationship expression between each sample and water surface evaporation intensity was established,and the comparison analysis with the measured data showed that among the 24 measured data,the number of the relative error calculated by the coefficient method was less than the relative error calculated by the alternative method was up to 19,accounting for 79.17%;in addition,the relative error can be from-16.42%?with the alternative method?to-1.78%?with the coefficient method?,which can be reduced by nearly 15%at the maximum,so the error calculated by the linear relationship was smaller.Finally,using Visual MODFLOW for numerical simulation,it was found that the change in E₀ not only directly affected the phreatic evaporation,but also indirectly caused changes in other recharge items and excretion items,resulting in the various changes in water level,water balance,and groundwater exploitation.It can be seen that there is a clear difference between E₀ and water surface evaporation intensity.In the absence of measured data,E₀based on water surface evaporation conditions can be obtained through a linear relationship,thereby improving the reliability of phreatic evaporation calculation.