High mountainous water resource systems are particularly sensitive to climate change impacts. The hydrological regime of such environments is strongly influenced by water accumulation in form of snow and ice and the corresponding melt processes. A modification of the prevalent climate and especially of the temperature can therefore considerably affect the hydrological regime and induce important impacts on the related water resources system. The present study analyses potential climate change impacts on the hydrological regime of a highly glacierized catchment in the Swiss Alps through an integrated simulation tool including namely a hydrological and a glacier evolution model and a model for the production of local climate change scenarios. The modelling of the hydrological behaviour of high mountainous systems is still a difficult task, especially because of the well-known data scarcity in high altitudes. In the present study, the uncertainties induced by each of the models are analysed and quantified through appropriate statistical methods. The obtained results show a statistically significant shift from the current so-called a-glacier regime (maximum monthly discharge in July and August) to a so-called nival type (maximum monthly discharge in June). The induced modification of the hydrological regime has a direct impact on the water use, on flood risks and on related ecological systems. For the presented case study catchment, these impacts are illustrated based on the main water use (hydropower production) and related risks for downstream inhabited areas.