Distributed Snowpack Simulation Using Weather Radar
with Hydrologic and Land Surface Models
Steven R. Fassnacht1, E.D. Soulis1, and N. Kouwen1
Hydrologic modeling to estimate peak spring snowmelt flows relies on an adequate representation of
the melt and runoff processes, as well as a satisfactory approximation of the quantity and condition
of the snowpack prior to or at the beginning of melt. For most modeling efforts, adequate assessment
of the state of the snowpack at the onset of melt has become the limiting factor in reliable snowmelt
hydrograph estimation. To address this, the snowpack is modeled continuously throughout the win-
ter, from accumulation to melt, using weather radar as the precipitation input.
The radar imagery that is used to approximate the accumulation of snow over the winter season is
adjusted for scaling errors, and variation in hydrometeor characteristics with temperature. The
hydrologic modeling is accomplished using a coupling of WATFLOOD, a distributed hydrologic
model developed at the University of Waterloo, and CLASS, the Canadian Land Surface Scheme
developed by Environment Canada. Both models use the Grouped Response Unit, or mosaic
approach, that considers land cover heterogeneity within computational units.
The results are the integration of four different datasets, namely, weather radar precipitation esti-
mates, measured and simulated meteorological parameters, field snowcourse data, and streamflow
hydrographs. The radar snowfall estimation is shown to be very similar to Nipher-shielded Belfort
precipitation gauge collection, after adjustment. Simulated snow depth and snow water equivalence
are shown to be quite comparable to observed values measured at snowcourses at most locations and
times. The modeling is validated by a good match between the computed hydrographs and the
observed hydrographs for 1993 at various streamflow gauge sites in central southern Ontario.
1
Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
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