A numerical and similarity analysis of infiltration into crusted soils

One‐dimensional, vertical infiltration of water through a crust of constant nonzero hydraulic resistance is theoretically examined in two ways, a numerical solution and a similarity reduction of the problem for early to intermediate times. The soil‐water content at the crust‐soil interface increases with time to approach a predictable final steady water content asymptotically. A greater proportion of the flow takes place at intermediate to low water contents, and without an appreciable effect of gravity, as the crust resistance increases. For the water content at the crust‐soil interface, the cumulative infiltration, and the wet front progress, simple expressions arise from the similarity reduction analysis, which is based on specific functional forms of the soil‐water diffusivity and suction head, and a relatively small initial soil‐water content. For early to intermediate times of flow, the similarity analysis describes adequately the calculated numerical solution flow data for Yolo soil. For intermediate to large times, a Green and Ampt type solution is linked to the similarity expression for cumulative infiltration with fair success.