Modelo preliminar de circulação de água subterrânea com suporte de métodos geofísicos eletromagnéticos e hidrogeoquímica, litoral de Cascavel – Ceará, Nordeste, Brasil

Abstract

The coastal zone of the city of Cascavel (58Km SE Fortaleza, Ceará, Brazil) was perforated for several groundwater wells during the past decade. In that area 10 wells extract groundwater from sediments of Barreiras Formation and from crystalline rocks. The variation of the outflow in this small area (1.5ha) was 1 to 14m3/h. The hydrochemical characterization held, among other findings, shows that the groundwater has two groups in terms of electrical conductivity (1000 and 300mS/cm). Since the proximity of the wells (150 to 200m) and the constructive characteristics could not be evoked to explain such variation in conductivity, so we sought a new hypothesis in this paper. A geophysical survey integrating the geophysical method of resistivity (electrical soundings) and the inductive electromagnetic method (FEM) was conducted with the objective to identifying the geoelectrical layers and the possible presence of lateral variation of resistivity/conductivity. After processing and inversion of all geophysical data some answers can explain the large variations of outflow and electrical conductivity in this area such as the presence of fractured zones and the variations of sedimentary and saprolite thickness.