Projections of future water resources and their uncertainty in a glacierized catchment in the Swiss Alps and the subsequent effects on hydropower production during the 21st century

Hydropower accounts for about 20% of the worldwide electrical power production. In mountainous regions this ratio is significantly higher. In this study we present how future projected climatic forcing, as described in regional climate models (RCMs), will affect water resources and subsequently hydropower production in downstream hydropower plants in a glacierized alpine valley (Vispa valley, Switzerland, 778 km(2)). In order to estimate future runoff generation and hydropower production, we used error-corrected and downscaled climate scenarios from regional climate models (RCMs) as well as glacier retreat projections from a dynamic glacier model and coupled them to a physically based hydrological model. Furthermore, we implemented all relevant hydropower operational rules in the hydrological model to estimate future hydropower production based on the runoff projections. The uncertainty of each modeling component (climate projections, glacier retreat, and hydrological projection) and the resulting propagation of uncertainty to the projected future water availability for energy production were assessed using an analysis of variance. While the uncertainty of the projections is considerable, the consistent trends observed in all projections indicate significant changes to the current situation. The model results indicate that future melt-and rainfall-runoff will increase during spring but decline during summer. The study concludes by outlining the most relevant expected changes for hydropower operations.