The process of rainfall infiltration into crusted soil has been the focus of many analytical and numerical studies. However, most of these studies have been supported by laboratory data because no field data were available. Following recent field experiments on crusted soils, which provided crust conductivity values using the disc infiltrometer technique, a simple two-layer Green and Ampt model is proposed. This model is of interest because it uses only measured variables-saturated hydraulic conductivity (K), pressure head, initial and saturated volumetric water content, and microscopic capillary length-as input data. Runoff in the model is calculated as the difference between cumulative rainfall and infiltration. Because actual runoff data is available and no parameter calibration is required, the comparison with model output serves as a validation test for the input data. Close agreement between measured and calculated runoff is found when the surface crust is considered, which demonstrates the importance of surface crusting and increases the confidence in the measured K values. It also shows that K measured at the 1-m2 scale remains a relevant parameter, even for the study of a process that involves a scale two orders of magnitude larger.
1Laboratoire d'étude des Transferts en Hydrologie et Environnement, UMR 5564 (CNRS, INPG, ORSTOM, UJF) BP 53, 38041 Grenoble Cedex 9, France. Dr. Vandervaere is corresponding author. E-mail: firstname.lastname@example.org
2ORSTOM, Laboratoire d'Hydrologie, BP 5045, 34032 Montpellier Cedex, France.
3Cooperative Research Centre for Catchment Hydrology, Dept of Civil Engineering, Monash University, Clayton 3168 VIC, Australia.
Received March 12, 1997; accepted July 29, 1997.