Evaluation of Non-Potable Groundwater Potential in Aquifers of the Municipality of Salvador, Bahia, Based on GOD Vulnerability Map

Abstract

This study evaluated the non-potable water potential of aquifers in the municipality of Salvador, Bahia, based on the GOD vulnerability map. The aquifers of Salvador have characteristics of fissural aquifer in the domains of the Crystalline Complex and, of granular aquifer in the domain of sedimentary rocks. The GOD method calculates the intrinsic vulnerability of the aquifer by numerically evaluating site hydrogeological parameters associated with aquifer type (from confined to unconfined), soil type (clay to sand), and depth to the top of the aquifer. The GOD methodology revealed that the natural vulnerability of the aquifers of the city of Salvador is classified from low to insignificant, in the most clayey and high topography of the city; and from high to extreme in the sandy parts of the valleys and lowlands. By mapping the vulnerability classes and outlining the sections from high to extreme vulnerability, it was possible to assess the potential of groundwater classified as non-potable, in view of the risk of contamination by anthropogenic activities installed in them or, to be installed. Taking the area of these sections and the hydrogeological characteristics of the aquifer, a non-potable water volume of approximately 20 million m³ was quantified, with an annual recharge of approximately 9 million m³, based on an annual recharge rate of 12% of rainfall on areas mapped as high and extreme GOD vulnerability. Thus, the vulnerability map favor an environmentally sound exploitation of a region's groundwater resources.