Monte Carlo simulation is employed to investigate the separate and simultaneous effect of horizontal heterogeneity of soil hydraulic properties and rainfall intensity on various statistical properties of the components of the one-dimensional water budget. One year of micrometeorological time series consisting of half-hourly values, generated with a one-dimensional climate model, constitutes the upper boundary conditions. Both a loamy and a sandy soil type are used. Spatial heterogeneity of rainfall is generated by disaggregation of the spatial mean rainfall. Compared with the annual water balance obtained using the scaled average soil hydraulic properties and spatial mean rainfall intensities, spatial heterogeneity of these induces significant changes in the mean values of the annual balance terms. Spatial variation of saturated water content has a negligible effect on the annual water balance and the dynamics of water storage. It appears that a homogeneous ''equivalent'' soil exists for the sandy soil but not for the loamy soil. ¿ American Geophysical Union 1996