Effect of Water Table Fluctuation on Barometric Pumping in Soil Unsaturated Zone

An analytical one-dimensional model for vertical transmission of barometric pressure in soil unsaturated zone has been developed to examine the effect of free boundary caused by water table. The model is applicable to a special case in which the water table moves in according to the pressure with high barometric efficiency. Ambient sinusoidal pressure fluctuation is assumed at the soil surface. The model with the numerical simulations results for an unsaturated zone with typical soil settings show a significant difference between the simulated pressure amplitudes for the case in which the water table is considered as a free boundary and the case in which the water table is considered as a fixed boundary. Maximum difference occurs at the water table. This result suggests the consideration of water table as a free boundary for cases in which the barometric efficiency of water table is relatively high.