The Valco S. Paolo site may be regarded as representative of the main Tiber valley in the urban area of Rome, which is located 2 km south of the city center. In recent years, as per level, temperature and electrical conductivity measurements conducted in gravel and sand aquifers have notable variations. For this purpose, heads observed from 15 piezometers and physical characteristic data of sand and gravel aquifers were monitored in 5 piezometers in the Tiber river by dataloggers during 4 months and integrated with available geological and hydrogeological information to develop a conceptual model of the system. These fundamental information are required to characterize the existing groundwater system in this area in order to establish a groundwater flow model. The validation of the conceptual model by a steady-state numerical groundwater flow model reveals that minimum change occur in the center. Trial and Error calibration method has been applied to this model. The calibrated model had been used to simulate a different set of field measurements and the verification showed a good degree of confidence.