Simulating topsoil drying-wetting dynamics as interrelated with infiltration and evapotranspiration

Infiltration is a process that water seeps through the ground surface into the unsaturated zone to replenish soil water. As a result of infiltration, the soil moisture will be increased from an initial to the naturally saturated soil moisture above which additionally infiltrated water will percolate to recharge the phreatic aquifer. Once infiltration ceases, the downward movement of soil water will continue until the soil moisture is reduced to the field capacity. The downward movement is termed redistribution and steadily leads to a more and more uniform vertical profile of soil moisture, ultimately approaching the field capacity. This chapter assumes that infiltration and redistribution primarily occur in the vertical direction and thus focuses on one-dimensional (1D) vertical movement. It illustrates the soil moisture dynamics due to infiltration or redistribution in a hypothetic homogenous soil horizon.