Modelling runoff in a Swiss glacierized catchment - Part II: daily discharge and glacier evolution in the Findelen basin in a progressively warmer climate

In the context of global warming, hydrological regimes in mountain areas are likely to be modified and will therefore result in significant impacts to the supply mechanisms for hydropower and other end-uses of water, both in the mountains themselves and in the lowland regions downstream. The main objective here is to attempt a fine and continuous analysis of the impacts of such changes on runoff and glaciers in a largely ice-covered catchment in the Swiss Alps: the Findelen watershed. The simulated daily discharge values have been obtained with a semi-distributed hydrological model called Routing System 3 (RS3.0). A stochastic weather generator has been used to generate a 110 year sequence of meteorological input datadescribed in a companion articlethat have been further perturbed in order to simulate a progressively warmer climate by the end of the century. The amplitude of atmospheric change is suggested by regional climate model simulations, under the A2 greenhouse-gas emissions scenario. Results show at first an increase of discharge (19.4% in about 60 years) due to the rapid melt of the glacier, followed by a large decrease in runoff at the end of the period (28% from the beginning to the end of the studied timeframe), primarily due to the depletion of the solid water reservoir. The glacier is indeed projected to lose 91% of its surface area. In parallel, a seasonal shift in flow patterns is also observed: the discharge values are high earlier in spring due to advanced snow and ice melt, while the rest of the curve flattens out. Copyright (c) 2012 Royal Meteorological Society