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Use and Hydrological Robustness of Time‐to‐Incipient‐Ponding
Author(s) -
White I.,
Sully M. J.,
Melville M. D.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300050007x
Subject(s) - sorptivity , ponding , hydraulic conductivity , loam , soil science , hydrology (agriculture) , surface runoff , geometric mean , mathematics , geotechnical engineering , soil water , environmental science , geology , geometry , drainage , ecology , porosity , biology
Both the use and hydrological robustness of time‐to‐ponding, t p , have been questioned recently. We examine these questions here for variable rainfall rates. Using a nondimensional analytic form for t p , we show that for rainfall rates, R , greater than about 1.5 times the saturated hydraulic conductivity, K s , t p is relatively robust. Only in the region K s ≤ R ≤ 1.5 K s is t p sensitive to small changes in R/K s . We also show a comparison between field measurements of t p 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 K s and sorptivity determined under ponded conditions with disc permeameters. The good agreement found, together with the ease and reproducibility of the field measurements, indicate that both the determination and prediction of t p are soundly based provided R > 1.5 K s . Finally, we use the analytic expression for t p 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 t p , R and the steady state runoff during rainfall. These hydraulic properties agree well with those measured under a constant head. We conclude that t p is a useful and hydrologically robust property provided R ( t p ) > 1.5 K s .