Case Study: Watershed Modeling with Distributed Weather Model Data

This paper presents the results of a modeling study that is part of a collaborative distributed precipitation-snowmelt-runoff modeling study initiated by B.C. Hydro (the electric utilities company in British Columbia). Meteorological data were generated for a 23 year period by a high-resolution boundary layer model using a grid size of 2 min latitudeX4 min longitude (3.7X4.7 km). The distributed daily precipitation and temperature-time sequences generated by this model were used as input to the WATFLOOD/SPL hydrological model, resulting in computed streamflows that were compared to measured streamflow at 32 flow gauging sites; and four reservoirs. In this way, through a number of calibration and validation runs, the whole sequence of generating the meteorological data and their subsequent use to drive the hydrological model was tested. The study shows the importance of using both models in combination. Although the boundary layer model used the observed meteorological data to the fullest extent, the hydrologic simulations revealed a significant north-south trend in the precipitation error field. This resulted in streamflow errors as high as 60%. A reanalysis of the fields using the modeled streamflow reduced the error substantially. With the exception of a few streamflow stations. the computed flows matched the observed streamflows and reservoir inflows very well.