Evaluation of intrinsic vulnerability the contamination of the karst aquifer in Cafarnaum region, Bahia

Abstract

The Salitre karst aquifer is located in the Sedimentary Carbonic Basin of Irecê, in the north-central region of Bahia, in the geological context of the Salitre Formation. It consists of thick sequences of calcarenites, calcilutites, calcissiltites and dolomites intercalated sometimes with subordinate continental sequences, constituted by silexites, sandstones, siltites, mudstones and marls. The main objective of the study is evaluate the intrinsic vulnerability to the natural contamination of the karst aquifer in Cafarnaum region, applying the COP methodology. It is well know that karstic aquifers are especially vulnerable to contamination due to their shallow depth, the high velocity of water flow, their direct connection to the surface and their recharge through open absorption forms. For the assessment of the natural vulnerability of the karst aquifer to contamination through the POP methodology, three hydrogeological parameters are considered: flow concentration, overlapping layers and precipitation regime. The analysis of the vulnerability map intrinsic to the contamination allowed the delimitation of four classes of vulnerability in the area: very high (12.5% - 70.20 km²), high (0.7% - 4.0 km²), moderate 28.0%, 154.41 km²) and low (58.7%, 330.00 km²). The individualization of the karstic features and their area of influence is the factor that played a significant role in the delimitation of the very high vulnerability class