Hydrological functioning of mediterranean mountain basins in Vallcebre,Catalonia: Some challenges for hydrological modelling

The Vallcebre research catchments are located in the south-eastern Pyrenees, in an area of diverse land use and varying levels of degradation, including forested hillslopes, abandoned agricultural terraces and badland areas. Outside the badlands, the hydrological response is controlled by saturation mechanisms. Between September and June the spatial patterns of saturated areas and soil moisture are determined by subsurface flow, modified by the premature saturation of the inner parts of agricultural terraces, and the negative soil moisture anomalies induced by forest patches overgrown in grassland areas. During summer, this behaviour ceases because of soil moisture depletion and badland surfaces are the only hydrologically active areas, producing excess runoff in response to the intense rainstorms. During the beginning and the ending of the wet season, the saturation of active areas shows a hysteretic behaviour that breaks the linearity between the mean water reserve of the basin and the relative saturated area. © 1997 John Wiley & Sons, Ltd.