Water Infiltration into Soil under Oscillating Precipitation Regimes

An analytical study of the problem of water infiltration into a homogeneous unsaturated soil showed that, in the case of periodical water recharge through the soil surface, the character of the flow will tend to uniform with the depth. The stabilization of the flow was found to be due to the effect of two factors: capillary dissipation and nonlinearity. The role of each factor was studied by constructing appropriate exact solutions. An estimate was proposed for the depth at which flow variations become insignificant. This estimate takes into account the joint effect of both these factors. An explicit expression for it contains the hydraulic characteristics of the soil and the main characteristics of the surface recharge regime. The pumping effect was also studied and it was showed that, at some assumptions regarding the soil hydraulic characteristics, it manifests itself in that the time-averaged water content in the top soil layers is less than that at greater depth.