Águas subterrâneas no Ceará – poços instalados e salinidade

Abstract

Groundwater exploitation in Ceará, northeast Brazil has grown. However, the actual potential is still unknown. Until year 2003 about 23,000 wells were installed. Around 63% were in the crystalline litology, 29% in the sedimentary, and the remaining in alluvial and karstic formations. Wells located in the crystalline basement showed specific flow (Qe) which represents 13% to those located in the sedimentary basins. Wells from this last litology are 35% deeper than those in the crystalline. The Metropolitan basin has the greatest number of wells installed followed by Salgado's basin. Considering the specific flow, the largest exploitation potential is in the Salgado basin followed by Baixo Jaguaribe. Groundwater from the crystalline possesses a larger saline content than from the sedimentary basin. Local empiric models can be used to predict the saline content in Ceará´s groundwater. Wells are the water source which supplies about 1.1 million people. Most of them are in the Salgado's basin and in the Acaraú´s. In the crystalline the agreement to potability standards reaches 47% while in sedimentary basin it reaches up to 90%. For irrigation purposes groundwater from crystalline litology shows a higher degree of restriction and special attention should be given to the toxicity of chloride ion.