APPROACHES TO CONTINENTAL-SCALE RUNOFF FOR INTEGRATED ASSESSMENT MODELS

The need to incorporate water resources into regional and global integ rated assessment models for evaluating global change impacts has been identified as being important, but given the spatial and temporal vari ability of freshwater resources and limited data availability, the inc lusion of water within these large scale models has proven to be diffi cult. A compromise between accurate representation of complex processe s and simplistic parameterization is necessary for capturing regional and temporal variability and to minimize computational requirements. A n analysis of Western Europe's and Africa's freshwater runoff, which s pans a range of climate variability, was performed at varying levels o f spatial aggregation and at both monthly and annual time steps. Model results showed that regional runoff characteristics were lost beyond a data aggregation of 1 degrees x 1 degrees resolution. A monthly soil moisture model proved to be adequate for assessing annual water avail ability, which is the scale often used in integrated assessment models . Simpler methods, such as an empirical annual model and a simple mont hly model did not consistently replicate annual historic runoff. (C) 1 997 Elsevier Science B.V.