Hydrogeological Mapping is a fundamental instrument for the exploration groundwater bodies, as well as for land use planning. The Hydrogeological Mapping of Portugal at the 1:200 000 scale is a core mission of the LNEG. LNEG carries out a permanent activity of inventory, evaluation and interpretation of hydrogeological information, covering quantitative and qualitative aspects of groundwater and its correlation with the different geological formations of the territory national. In addition to official hydrogeological mapping, LNEG produces hydrogeological maps of a thematic nature, including contamination and vulnerability, at different scales, accompanied by explanatory notes. In support of the hydrogeological mapping, LNEG is also responsible for the organization and harmonization of hydrogeological data in Geographic Information Systems with a view to interoperability of data and services in the EU.