Modeling snowdrift distribution in a small mountain watershed: Spatial and temporal scale limitations

A model of total yearly accumulation using daily degree days and monthly snow covered areas from aerial photoswas tested against a 25 m gridded probe survey for the years 1990, 1992, and 1993. Agreement of the model with the survey was within ± 5% which is the estimated accuracy of the probe surveys. The snow depth distribution for the survey years was modeled by assigning depth contour values, derived from the degree day model, to the edges of the snow drifts delineated on the aerial photos. The rational was simply that shallower snow had melted away and deeper snow remained. The correlation between the modeled snow distribution and the probe survey was very good down to a resolution of approximately 1 hectare when the correlation became poor. The poor correlation at finer resolutions was attributed to the coarse spatial resolution of the 25 m probe survey and the coarse time resolution of the monthly aerial photos.