Impact of initial and boundary conditions on preferential flow

Preferential flow in soil is approached by a water-content wave, WCW, that proceeds downward from the ground surface. WCWs were obtained from sprinkler experiments with infiltration rates varying from 5 to 40 mm h− 1. TDR-probes and tensiometers measured volumetric water contents θ(z,t) at seven depths, and capillary heads, h(z,t) at six depths in a column of an undisturbed soil. The wave is characterized by the velocity of the wetting front, cW, the amplitude, wS, and the final water content, θ⁎. We tested with uni-variate and bi-variate linear regressions the impacts of initial volumetric water contents, θini, and input rates, qS, on cW, wS and θ⁎.The test showed that θini influenced θ⁎ and wS and qS effected cW. The expected proportionality of wS ≈ qs1/3 was weak and cW ≈ qs2/3 was strong.