ABSTRACT
The Brazilian orogenic cycle activities lasted up to the Upper Ordovician/Lower Silurian whereby the actual tectonic framework of the Brazilian territory has been built. The geologic framework described before and the assessment of the water well logs and oil soundings suggest that the Alter do Chao formation is the main regional aquifer functioning under an unconfined regime. The issue regarding the high heterogeneity and anisotropy of the fractured media depends directly on the assessment scale. The hydrogeological map of Brazil, launched by the Brazilian Geological Survey—CPRM/SGB at the end of 2014, represents a synthesis of the hydrogeological information data sets available in the country. The concept of "hydrographic regions" defined by the Water Resources National Council—CNRH has been adopted. The geological database was obtained from the geographical information systems Bazil from the CPRM and based on a simplification of unit attributes and conversion into hydrogeology characteristics, such as groundwater transmissivity and storage.
