Assessing the Effect of Climate Change on River Flow Using General Circulation Models and Hydrological Modelling – Application to the Chaudière River, Québec, Canada

s part of a wider study on the adaptation of agricultural land use to climate change (CC), this paper presents an assessment of possible future hydrological regimes of the Chaudière River watershed, Québec, Canada. We first present a review of the various methods used to integrate outputs of General Circulation Models (GCMs) into hydrological models that are applied at a local scale. Following this review, the delta method, statistical downscaling, and a combination of both methods were selected for this investigation. Data from different GCMs (in the case of the delta method) corresponding to different gas emission scenarios and simulation members were also considered to provide a range of possible future conditions. We used the integrated modelling system GIBSI, which is based on the distributed hydrological model HYDROTEL, to simulate streamflows for a reference period (1970-1999) and a short-term future period (2010-2039). For all three methods, results show a slight decrease in annual runoff (-5% on average). On a monthly scale, the effect is more heterogeneous depending on the method used, showing, in most cases, an increase in water discharge in the winter due to higher temperature and a decrease during the summer and fall. When using statistical downscaling, spring peak flow decreased slightly (-6.7% on average) while summer base flow remained unchanged. This study highlights the importance of using different methods and different sources of data in the assessment of potential CC effects on watershed hydrology.