Runoff generation in an intensively disturbed, abandoned farmland catchment, Central Spanish Pyrenees

Abstract

22 Pag., 3 Tabl., 7 Fig.This paper studies the hydrological response to rainstorm events of a small experimental catchment in the Central Spanish Pyrenees. The Arnás catchment was cultivated until 40 years ago, and then abandoned and affected by plant recolonisation, especially shrubs. A rainfall of a few millimeters is enough to produce a sudden increase in discharge, due most probably to the steep gradients and the small size of the catchment and the extensive areas with low vegetation density and thin soils. The intensity of the response shows a very high variability, depending on the intensity of precipitation and soil humidity conditions before the flood. This paper identifies two types of floods according to the relationships between precipitation and discharge, and confirms that antecedent soil moisture explains much of the response. The shape of the hydrograph, very similar to the hyetograph, suggests that the Arnás catchment is dominated by overland flow processes. However, more intense rainstorms do not generate higher peak flows, thus demonstrating the existence of different runoff-generating areas.This paper has been supported by the following projects: “Water resources management in a changing environment: the impact of sediment on sustainability” (WARMICE, ENV4-CT98-0789) funded by the European Commission; and “Assessment of sediment sources and runoff generation areas in relation to land use changes” (HIDROESCALA, REN2000-1709-C04-01/GLO), “Hydrological processes in seminatural Mediterranean areas” (PROHISEM, REN 2001-2268-C02-01/HID), and “Hydrological processes in Pyrenean catchments in relation to land use and climate changes” (REN 2003-08678/HID), all funded by the CICYT. Monitoring of the catchment has been supported by agreement between the CSIC and the Spanish Ministry of Environment (RESEL).Peer reviewe