Seasonal differencesin a small farmland abandoned catchment, Central Pyrenees

Abstract

This study shows that the relationships between rainfall and runoff at the event scale in a small farmland abandoned catchment are not linear and that the hydrological response is linked to the antecedent wetness conditions. Rainfall and baseflow discharge have a pronounce influence on the value of the runoff coefficient, while rainfall intensity affects the maximum discharge increment. Watertable data show high seasonal dynamics, with a dry period during summer, a wet period during winter and spring, and a transition period characterised by a high spatial variability. The analysis of the hydrological information at the event scale allows the distinction of three types of event, and reveals the occurrence of different runoff generation processes within the catchment. During dry conditions, the hydrological response is very low and infiltration excess over localised areas is ikely to be the main runoff process. As the catchment gets wetter, saturated excess runoff (and probably subsurface flow) becomes the dominant runoff process.