On the scale problem in hydrological modelling

The problem of scales and particularly the modelling of macro or continenta l scale catchments in hydrology is addressed. It is concluded that the magn itude of the scale problem is related to the specific hydrologic problem to be solved and to the scientific approach and perspective of the modeller. A distributed modelling approach, based on variability parameters, is sugge sted for modelling of soil moisture dynamics and runoff generation. It is s hown that the parameters of such an approach are relatively stable over a w ide range of scales. An example of the application of a standard Version of the Swedish HBV hydrological model to the continental scale catchment of t he Baltic Sea is shown and its usefulness is discussed. (C) 1998 Elsevier S cience Ltd. All rights reserved.