Identification of aquifer parameters in transient state: The extended uniqueness of the solution

A conceptual simplified model of an aquifer has been developed for preliminary tests, in order to derive useful information for the final model. The modelled aquifer has been divided into a number of homogeneous zones, according to a priori hydrogeological information. A realistic experiment has then been numerically simulated in order to assess the identifiability of the relevant flow parameters. The parameter identification is carried out using a constrained optimization algorithm, stopping the optimization process when the misfit has reached an assigned value related to the data noises. The optimization algorithm used is a ''non-local'' one. The optimization procedure has been repeated by starting from different points of the admissible parameter space. Since the results show that the identified parameter Values are within a restricted zone of the parameter space, we state that these solutions constitute the unique ''extended'' solution.