TOWARD IMPROVED CALIBRATION OF HYDROLOGIC-MODELS - MULTIPLE AND NONCOMMENSURABLE MEASURES OF INFORMATION

Several contributions to the hydrological literature have brought into question the continued usefulness of the classical paradigm for hydro logic model calibration. With the growing popularity of sophisticated ''physically based'' watershed models (e.g., land-surface hydrology an d hydrochemical models) the complexity of the calibration problem has been multiplied many fold. We disagree with the seemingly widespread c onviction that the model calibration problem will simply disappear wit h the availability of more and better field measurements. This paper s uggests that the emergence of a new and more powerful model calibratio n paradigm must include recognition of the inherent multiobjective nat ure of the problem and must explicitly recognize the role of model err or. The results of our preliminary studies are presented. Through an i llustrative case study we show that the multiobjective approach is not only practical and relatively simple to implement but can also provid e useful information about the limitations of a model.