Macroscale hydrological modelling with GCM climate data

General circulation models (GCMs) perform vertical water and energy balances at 20 or 30 minute time intervals for grid points 2-4deg apart but generally contain no information on the land-phase transfer of water between grid points or within watersheds. This study used a distributed hydrological model with data output from the Canadian Climate Centre’s GCM. A water balance was carried out at 12-hour time intervals for a 10-year period using GCM grid points in and surrounding the 1.6 million km² Mackenzie River Basin in north-western Canada. The water surpluses from each grid point were accumulated to provide a simulated hydrograph at the outlet of the Mackenzie Basin. The hydrological model was calibrated and verified using five years of recorded climatological and hydrometric data as well as land cover data from NOAA AVHRR images. The climatological outputs from the GCM were then used as inputs to the hydrological model, generating a further hydrograph for the Mackenzie River. It was found that, by itself, the GCM overestimates water excesses or runoff within the basin and that using a hydrological model with the GCM climatology produces a better representation of the recorded flow regime. The method allows verification of a GCM performance.