Differences in gravity-dominated unsaturated flow during autumn rains and snowmelt

Five tracer experiments have been performed in a coarse-textured soil near the new main airport at Gardermoen, Norway. In two lysimeter walls, 30 and 40 measuring points form the basis for spatial moment calculations. Althoug h experiments were performed under:different meteorological conditions (aut umn and snowmelt) and at two different sites, the ratios of centres of vert ical mass over cumulative infiltration were of the same order of magnitude, indicating a gravity-dominated flow. Two-dimensional transport simulations with SUTRA (Voss, 1984), with a priori estimated input parameters and rand om fields of soil hydraulic properties revealed a relatively good agreement with the experimental results. Three possible sources of heterogeneity aff ecting the vertical displacement of solute during snowmelt were identified: variability of soil physical properties, soil surface elevations and varia bility of ground frost during the melting period. To obtain accurate predic tions, soil heterogeneity was the most important factor to characterize for the coarse-textured soil under consideration. Copyright (C) 1999 John Wile y & Sons, Ltd.