Validation of a distributed hydrological model against spatial observations

In connection with climate change studies a new hydrologic field has evolve d - regional hydrological modelling or hydrologic macro modelling, which im plies repeated application of a model everywhere within a region using a gl obal set of parameters. The application of a physically based distributed h ydrological model ECOMAG to river basins within the NOPEX southern region w ith this purpose in mind is presented. The model considers the main processes of the land surface hydrological cyc le: infiltration, evapotranspiration, heat and water regime of the soil, sn owmelt, formation of surface, subsurface and river runoff and groundwater. The spatial integration of small and meso-scale non-homogeneity of the land surface is a central issue both for the definition of fundamental units of the model structure and for determination of representative values for mod el validation. ECOMAG is based on a uniform hydrological (or landscape) uni t representation of the river basin, which reflects topography, soil, veget ation and land use. As a first step the model was calibrated using standard meteorological and hydrological data for 7 years from regular observation networks for three basins. An additional adjustment of the soil parameters was performed using soil moisture and groundwater level data from five smal l experimental basins. This step was followed by validation of the model ag ainst runoff for 14 years from six other drainage basins, and synoptic runo ff and evapotranspiration measurements performed during two concentrated fi eld efforts (CFEs) of the NOPEX project in 1994 and 1995. The results are p romising and indicate directions for further research. (C) 1999 Elsevier Sc ience B.V. All rights reserved.