Regional Calibration of Watershed Models

1. INTRODUCTION As watershed models become increasingly sophisticated and useful, there is a need to extend their applicability to locations where they cannot be calibrated or validated. It is only natural that as watershed models, computer technology and hydrometeorologic data sources continue to evolve, there will be an ever increasing need to apply watershed models where streamflow data is unavailable for calibration. Without streamflow data, a watershed model cannot be calibrated or validated, hence regional methods are needed which relate easily measured watershed characteristics to watershed model parameters. The focus of this chapter is on a review of the various approaches which have been taken for estimating watershed model parameters in situations when streamflow data is unavailable for model calibration and validation. In the past decade, there has been a significant increase in research relating to the regional calibration of watershed models to enable their use at ungauged sites. The increased importance of regional methods for estimating watershed model parameters is influenced by and related to the following emerging themes: