ANALYTICAL COMPENSATION BETWEEN DTM GRID RESOLUTION AND EFFECTIVE VALUES OF SATURATED HYDRAULIC CONDUCTIVITY WITHIN THE TOPMODEL FRAMEWORK

The recent widespread availability of digital terrain data has resulte d in increasing use, in a variety of hydrological models, of different degrees of complexity. Previous experience suggests that neither mode l results nor effective parameter values are independent of the resolu tion of the digital terrain data used. Calibration of parameter values can compensate for lack of resolution in the digital terrain data. Th is paper will show, for one particular model, TOPMODEL, how an analyti cal link can be established between the grid size of a raster digital terrain model and the effective saturated hydraulic conductivity value used in the model. The work generalizes the results of the recent stu dy by Franchini et al. (1996) and allows the change in effective condu ctivity to be estimated on the basis of keeping a realistic simulation of saturated contributing areas as the DTM grid size changes. (C) 199 7 by John Wiley & Sons, Ltd.