Experimental Study On Water Migration At Water-Soil-Gas Interface In The Vadose Zone Of The Piedmont Plain Of Hebei Province

The Hebei Plain is an important agricultural product production area in China.The demand for water resources in this area is huge,and research on issues related to water resources development and utilization is urgently needed.This research relies on the groundwater science and engineering field test base of the Ministry of Natural Resources(Zhengding)to carry out experimental research on the atmospheric precipitation-gas-bearing water-groundwater conversion process.Among them,the water surface evaporation and phreatic evaporation experiments are carried out to study the factors affecting water surface evaporation,the factors affecting phreatic evaporation,the law of precipitation infiltration and the relationship between water-air interface and water-gas interface,revealing the water-soil-gas interface.The water exchange process provides theoretical basis and technical support for the rational development and utilization of water resources in the region.First of all,this study analyzed the evaporation law of water surface by using nine different types of evaporator water surface evaporation tests,and calculated the conversion coefficient between evaporations of different evaporators.Under meteorological conditions in the study area,the evaporation intensity of the water surface is mainly affected by temperature,humidity,wind speed,water vapor pressure and solar radiation.The relationship between evaporator diameter D and E/E601 is in logarithmic function relationship,ie E/E601 =-0.12 ln D + 1.6143(where R2 = 0.8801).E601 evaporation is converted to 20m2 evaporation pond evaporation volume average conversion coefficient is 0.86,AM3-200 evaporation is converted to 20m2 evaporation pond evaporation volume average conversion coefficient is 0.64,AM3-200 evaporation is converted to E601 evaporation volume average conversion coefficient is 0.76.Secondly,in this study,the phreatic evaporation test of three kinds of lithologic evaporation drums,such as sandy clay loam,sandy loam and loam,was carried out at different water level depths,and the daily evaporation amount and the buried depth data were fitted.It is indicated that the depth of phreatic evaporation in sandy loam,loam and sandy loam is about 3m,2m and 3m respectively.The evaporation in sandy loam and sandy loam is exponential function function,and in loam.The power function relationship is the same;under the experimental conditions,the burial depth of the best recharge in sandy loam,loam and sandy clay loam is about 3-4m,2m,2m.Finally,this study compares and analyzes the water surface evaporation test and the diving limit evaporation test,and concludes that the diving limit evaporation(Es)and the water surface evaporation(Ew)are exponential.Among them,the limit of evaporation in the sandy loam is Es=1.9457Ew0.5266(R2 = 0.9168),and the limit of evaporation in the loam is Es=1.3062Ew0.5747(R2 = 0.9889),and the limit of evaporation in sandy clay loam is Es=0.7436Ew0.774(R2 = 0.9155).