A procedure for the selection of objective functions for hydrologic simulation models

Hydrologic simulation models are calibrated by comparing observed data with data generated by the models. The comparison is made in an optimization procedure using an objective function adopted for that purpose and a set of data which is a subset of all data available or observable. The choise of the set of data and of the objective function to be used for any given model is a subjective decision which influences the values of the model parameters and the performance of the model. The set of data used should be comparable to the engineering application for which the model is intended. The objective function can be chosen by a procedure outlined in the article in which a number of possible functions are considered and compared with reference to one or more engineering applications.