Calibration of process-oriented models

Model calibration is a critical phase in the modelling process, and the need for a well-established calibration strategy is obvious. Therefore a systematic approach for model calibration is proposed which is guided by the intended model use, and which is supported by adequate techniques, prior knowledge and expert judgement. The success of calibration will be primarily limited by the nature, amount and quality of the available data, in relation to the complexity of the model; additional limitations are the effectiveness of the applied techniques and the availability of time, man- and computer power, adequate expertise and financial resources. These limitations will often preclude a unique calibrated model. As a consequence, calibration studies should provide information on the non-uniqueness and/or uncertainty which will be left in the model (parameters) after calibration, and this uncertainty should be adequately accounted for in subsequent model applications.