LAUSR

Finger flow in water-repellent (WR) soils significantly influences the transport of water and solutes in the soil, but the mechanics of finger flow occurrence in layered WR soils is not clear. Soil chamber infiltration experiments with a total of 20 treatments, including five different WR levels with four layer combinations, i.e., clay or sandy loam overlying sand or heavy gravel, were conducted to reveal the mechanics of finger flow occurrence in layered WR soils. The variations of the finger flow dynamics and infiltration parameters were investigated. The results showed: (i) the temporal variations of cumulative infiltration (CI) decreased with the increase of the WR level so that CI was generally larger when the top layer was sandy loam rather than clay loam and therefore the top layer soil texture controlled CI more than the sublayer; (ii) for the wettable treatments, finger flow was clearly and uniformly generated in layered soils with a sublayer of heavy gravel rather than sand, but for WR layered treatments, fingers developed irregularly with the WR levels and finger length, width, and velocity varied with the WR levels; (iii) there were good power function or linear correlations between CI and cumulative wetting area, and between CI and finger length; and (iv) water content in the top layer was higher than in the sublayer and generally decreased with the increase of WR level. Finger flow development in layered WR soils was generally irregular and showed a large degree of complexity.