l. Introducción El conocimiento de la respuesta hidrológica de una cuenca hidrográfica es necesario para distintos fines, desde la estimación de los caudales generados por las tormentas hasta la evaluación del impacto que producen los cambios de uso del suelo en el ciclo del agua (Grayson et al.,1992).

The antecedent soil moisture status of a catchment is an important factor in hydrological modelling. Traditional Hortonian infiltration models assume that the initial moisture contení is constant across the whole catchment, despite the fact that even in small catchments antecedent soil moisture exhibits tremendous spatial heterogeneity. Spatial and temporal patterns of soil water distribution were studied in a burnt zone with little vegetation and an unburnt zone with a greater vegetal cover. Severa! transects were installed across transects at the study área.At the transect scale, when the factors affecting soil moisture were limited to topographical position or local topography, spatial patterns showed time stability, but when other factors, such as vegetation were taken into account, the spatial patterns became time unstable. At the point scale, and in the same áreas, topographical position was the main factor controlling time stability. Scale dependence of time stability was studied and local topography and vegetation presence were observed to play an important role for the correlation between consecutivo measures depending on the scale.