Modeling Mackenzie Basin Surface Water Balance during CAGES with the Canadian Regional Climate Model

Abstract

The Canadian Regional Climate Model has been used to estimate surface water balance over the Mackenzie River basin during the water year 1998–99 in support of the Canadian Global Energy and Water Cycle Experiment (GEWEX) Enhanced Study (CAGES). The model makes use of a developmental third-generation physics parameterization package from the Canadian Centre for Climate Modelling and Analysis GCM, as well as a high-resolution land surface dataset. The surface water balance is simulated reasonably well, though Mackenzie basin annual mean daily maximum and minimum temperatures were both colder than observed by 1.7°C. The cold bias contributed to a longer snow-covered season and larger peak snow water equivalent than was observed, though snow accumulated realistically compared with two independently observed estimates after 1 November. Mackenzie basin annual precipitation was simulated as 496 mm, about 9% larger than observed, and P − E was 225 mm. Net soil moisture change during this water year was found to be −26 mm, though because of a spinup problem in the Liard subbasin, the value is more likely closer to −14 mm. The simulation was used to drive offline two different hydrologic models in order to simulate streamflow hydrographs at key stations within the Mackenzie basin. Results suggest that when subgrid-scale routing and interflow are included, streamflow timing is improved. This study highlights the importance of orographic processes and land surface initialization for climate modeling within the Mackenzie GEWEX Study.