HR: 09:30h
AN: H41B-04 INVITED     [Abstracts]
TI: Use of Time to Incipient Ponding as a Hydropedologic Index for Surface Soils
AU: * Smettem, K
EM: smettem@cwr.uwa.edu.au
AF: The University of Western Australia, Centre for Water Research, Nedlands, WA 6009 Australia
AU: Watanabe, F
AF: Tokyo University of Agriculture, Faculty of Regional Environment Science, 1-1-1, Sakuragaoka, Setagaya, Tokyo, 156-8502 Japan
AB: Physically-based hydrological modeling using numerical solutions to Richards equation requires considerable parameterization in order to specify the relations between the soil water pressure head and the soil water content and between the hydraulic conductivity and either the soil water content or soil water pressure head. The problem is exacerbated in catchment hydrologic applications because the physical parameters vary spatially and some even vary temporally. This difficulty of parameter acquisition has led to a widespread interest in development of pedotransfer functions to derive the requisite properties from more basic data. It has also resulted in attempts to simplify spatial data input requirements by identifying domains of sensitivity (with respect to model outputs) as functions of soil type, usually on the basis of texture. For classifying the runoff potential of soils, one important hydrologic characteristic is the time to incipient ponding. Estimations of incipient ponding can be obtained numerically using Richards equation and `like soils' grouped on the basis of pedotransfer inputs derived from the texture triangle. Alternatively, predictions can be made using quasi-analytic infiltration theory containing only two parameters of importance: the sorptivity, S, (which has a dependence on initial moisture content) and the saturated hydraulic conductivity. This considerably simplifies the grouping of `like soils' and provides one objective index for hydropedologic mapping of surface soils. In this paper we discuss the relation between Sorptivity and other hydraulic parameters and then use estimations of time to incipient ponding to map this hydropedologic index onto the USDA texture triangle.
DE: 1800 HYDROLOGY
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1899 General or miscellaneous
SC: Hydrology [H]
MN: 2005 Joint Assembly