3D LITHOSTRATIGRAPHIC MODEL AS SUPPORT FOR DEVELOPMENT OF A GROUNDWATER FLOW MODEL: THE SARNO PLAIN (ITALY) CASE STUDY

The aim of this paper is to identify a computer based methodology in order to draw up a lithostratigraphic 3D model of an aquifer so as to develop a groundwater flow model in a part of it, useful to define some parameters involved in the evaluation of the water balance. The methodology was applied in two sample areas located in the Sarno Plain (Italy) affected by strong groundwater subflow. The stratigraphical reconstruction of the study areas was obtained by interpolating stratigraphical data from analyzed and codified boreholes. The software used for the lithostratigraphic model creation is Rockworks 2006, which allows the construction of a 3D model (using grid-models or voxel matrix models) and its three-dimensional or bi-dimensional representation. Starting from the obtained lithostratigraphic model, a numeric model was implemented to simulate the flow in the groundwater bodies. The software used to reach this aim is Groundwater Vistas 5, which supplies a graphic interface for MODFLOW, a finite-difference model useful to study the groundwater flow. The methodology used has allowed to value the entity of the groundwater subflow coming from carbonate structure of the Lattari Mts. and from the volcanic aquifer of Somma-Vesuvious towards the Sarno Plain.