Use and Hydrological Robustness of Time-to-Incipient-Ponding

Abstract

Using a nondimensional analytic form for time-to-ponding, tp, for rainfall rates, R, greater than about 1.5 times the saturated hydraulic conductivity, Ks, tp is relatively robust. Only in the region Ks ≤ R ≤ 1.5 Ks is tp sensitive to small changes in R/Ks. A comparison between field measurements of tp using a rainfall simulator on a structurally unstable, sodic and saline gravelly silty clay loam and those predicted using the analytic expression and measured values of Ks and sorptivity determined under ponded conditions with disc permeameters are shown. Results indicate that both the determination and prediction of tp are soundly based provided R > 1.5 Ks. The analytic expression for tp is used in the inverse sense to determine the soil's sorptivity, hydraulic conductivity and characteristic mean pore size, a measure of soil pore structure, from values of tp, R and the steady state runoff during rainfall. These hydraulic properties agree well with those measured under a constant head. Concludes that tp is a useful and hydrologically robust property provided R(tp) > 1.5 Ks. -from Authors Show more