Can we calibrate a complex groundwater model just by running an automatic calibration code? A case study from Italy: the Acque Albule Plain model (Rome)

This note presents a model calibration experience on a complex groundwater system located in central Italy, in the subsiding Acque Albule Plain near Rome (Italy).There are two main aquifers in this system. The first one, partially confined by Pliocene-Pleistocene deposits, is constituted by the limestone fractured bedrock, while the second one, unconfined, is within the fractured travertine. These two aquifers are connected in correspondence of the center of the plain, where deep hydrothermal water, starting from the limestone bedrock, upwells through the Plio-Pleistocene deposits in to the travertine.A.A. ground water model is applied to a 55km2 and is developed using Modflow-2005, discretized by 100x100 meters cells and three layers. Calibration process applied to this model consisted in several steps using estimation methods along with sensitivity analysis and geology information.The final model fitting shows clearly the importance of applying not only automatic estimation methods for calibration processes but also the need to be prepared to change own conceptual model starting from sensitivity analysis and from collecting new data to better understand the system.