Modelli tessiturali tridimensionali in acquiferi eterogenei

The suggested method concerns detailed quantitative rebuilding of textural characteristics of the subsoil in plain areas. The key point of the proposed approach relates to the organisation, georeferencing and code translation of stratigraphic data pertaining to water wells present in the study area. Stratigraphic data is stored and codified in a specific hydraulic database, TANGRAM, in order to assign percentage values for each textural class (gravel, sand, clay) to each well level. This data is then extracted and processed using three dimensional modelling software, GOCAD. Spatial data of the study area (topographic surface and aquifer bottom) is processed using an external GIS or directly on the GOCAD, to build a 3D grid between the two surfaces resulting in proportionally shaped cell thickness values. Gravel, sand and clay (textural class) percentages are assigned to each cell located in association with each georeferenced well using the "Discrete Smooth Interpolator" (DSI Mallet 1992) or geostatistic techniques. Values are interpolated in every dimensional cell of the grid to provide the 3D reconstruction of subsoil textural distribution. Processing can refer to either shallow or deep aquifers. An example of this method was used in the plain area in Alessandria (Piemonte, North-west Italy) and is illustrated in this paper and the relative codified stratigraphic files of the wells have already been completed. 3D rebuilding of subsoil textural distribution can be used as an input data starting point for many hydrogeological applications, such as mass-balance evaluation of a hydrogeological system, groundwater flow and pollutant transport models.