Assessment of groundwater availability in the Milan Province aquifers

Management programs often give less importance to groundwater because it is less visible than surface water, but this invisible resource, drawn from wells and springs, makes up about 10% of the requirements for irrigation and 95% of the water needed for civil use (drinking water, water for non-drinking purposes, fish-farming, etc.) in Lombardy. This study aims to provide a quantitative evaluation of the potential of the groundwater reservoir in the Milan province, through the integrated use of databases and models which permit the simultaneous management of large amounts of data. In fact, information on more than 7000 wells in the Milan province has been coded and stored in a special hydrogeological database, which permits a three-dimensional definition of the geometrical and hydrogeological characteristics of the subsurface system. The parameterisation of hydrogeological properties, such as effective porosity, helps to estimate the potential quantity of water stored in subsurface deposits throughout the whole provincial territory (approximately 34 billion cubic metres of water). Only a part of this is made up of mobile water, that is, the water that permeates medium and coarse materials (porosity over 17%), for a total of about 13-15 billion cubic metres of water. The variations of this groundwater reservoir depend on the piezometric level, the system’s reaction to the static and dynamic characteristics of the hydrogeological system itself and make up the net balance of the system. The estimation of the quantities of available both free and stored water volumes, is considered the best approach for simulating the effect of different impacts on resources, whether natural and/or man-made.