Fernando Antonio Carneiro Feitosa, CPRM - Serviço Geológico do Brasil, DEHID - Departamento de Hidrologia, fernando.feitosa@cprm.gov.br
About 50% of the surface of the Northeast region of Brazil is constituted by Precambrian rocks, generically called crystalline rocks. In these rocks groundwater systems occur as interconnected cracks, fractures and discontinuities, forming discontinuous random reservoirs showing small dimensions. Electrical conductivity data from 18,600 wells suggest the existence of a qualitative zoning, characterized by fresh water belts alternating with brackish to salt water belts. The reasons for this zoning are not well known. Some evidences, nevertheless, point to the geomorphology and factors associated with it, as playing important role in the matter. As to quantitative aspects, any try of resource evaluation would be untruthful. Nevertheless, it is believed that the amount of water that can be withdrawn from these rocks is sufficient to meet the needs of, at least, part of the scattered population and herds living in the Brazilian semi-arid areas. The human consumption of groundwater, however, in areas of poor chemical quality, requires the development of sustained desalination programs.
Keywords – Água Subterrânea; Rochas Cristalinas; Qualidade da Água