Air Pressure in the Vadose-Zone Calculation and Its Impact on Infiltration Simulation

Air pressure change in the rainfall infiltration in the soil affect the soil infiltration capacity,infiltration of water when the air pressure in the vadose zone is greater than the Earth's surface atmospheric pressure plays the role of the backwater.Theoretical analysis of general laws of the air movement in the vadose zone was given according to the observations of air pressure change in the vadose zone,which was a basis for assuming the air escaping function and deriving the formula of the air pressure change.And then the impact on the infiltration was simulated considering the vadose zone pressure change.Under the uniform rainfall conditions,the start time of the water accumulating was shifted earlier and the average infiltration rate was reduced by 27%,sometimes up to 32%;the difference of total penetration was little in the early time of rainfall,but became great at the period of compression escape and the difference was greater when the reduction of infiltration became more significant and longer,.the total infiltration for 24 hours average reduced by about 20%.