Distributed parameterization of a large scale water balance model for an Australian forested region

The parameterization of a large-scale hydrological model (RHESSys) for a forested region is described. Using the GRASS GIS, a range of topographic, vegetative, climatic, and edaphic parameters were mapped over the region. A regional DEM was validated by ground-truthing and shown to give an excessively smooth representation of the terrain which influences moisture distribution predictions. LAI was mapped by regressing shade-corrected satellite imagery against ground-based measurements and applying the regression equations to the imagery. Precipitation was mapped using both elevation lapse rates and a more data-intensive 3D spline interpolation, the latter proving more appropriate. Areal estimates of soil properties were made through inverse determination from baseflow analysis but a regional distribution was not performed. These diverse improvements to previous parameterization techniques are discussed with respect to their likely effect on RHESSys operation.