In alpine catchments, the nature of hydrological sources and stores varies in both space and time. This thesis presents an investigation of the processes controlling the stream hydrograph in three nested sub-catchments within a small alpine catchment (the TaillonlGabietous catchment) in the French Pyrenees. The study conducts fieldwork and modelling in parallel to allow the independent corroboration of hypotheses from different sets of analytical and field techniques. Meteorological. hydrological and hydrochemical data were collected during the 1996 and 1997 summer ablation seasons. Three key observations are made following analysis of this data. First, a temporal compensation effect is observed between summer meltwater runoff and the more prolonged discharge of groundwater throughout the winter. Second. the importance of precipitation events over the ablation season in this climatically sensitive area is recognised. Third. it is suggested that it is unrealistic to assume watertight catchments in many alpine areas. A conceptual model is presented of the hydrological processes controlling the stream hydrograph in an alpine glacierized catchment with an underlying groundwater system. Links to concurrent projects on glacier hydrometeorology. climate change. and stream ecology significantly enhanced the overall conclusions of the thesis.