SCALE AND MODELING ISSUES IN WATER-RESOURCES PLANNING

Resource planners and managers interested in utilizing climate model o utput as part of their operational activities immediately confront the dilemma of scale discordance. Their functional responsibilities cover relatively small geographical areas and necessarily require data of r elatively high spatial resolution. Climate models cover a large geogra phical, i.e. global, domain and produce data at comparatively low spat ial resolution. Although the scale differences between model output an d planning input are large, several techniques have been developed for disaggregating climate model output to a scale appropriate for use in water resource planning and management applications, With techniques in hand to reduce the limitations imposed by scale discordance, water resource professionals must now confront a more fundamental constraint on the use of climate models-the inability to produce accurate repres entations and forecasts of regional climate. Given the current capabil ities of climate models, and the likelihood that the uncertainty assoc iated with long-term climate model forecasts will remain high for some years to come, the water resources planning community may find it imp ractical to utilize such forecasts operationally.