Hydrogeological Characterization of Karst Tributaries of the San Franciscan Depression, River Corrente, West Bahia, Brazil

Abstract

Brazilian economy has experienced substantial growth in the last decade. Balancing economic development and the associated increase of water consumption with environmental sustainability is a challenge for both society and government. Karst aquifers are important freshwater resources for the growing population in some regions of Brazil. The west region of the state of Bahia is known for its abundant water resources. Corrente River (basin surface: 42,732 km²), provides ca. 30 % of the total water flow of the Sao Francisco River (basin surface 631,133 km²). During recent years, Bahia’s state has undergone a marked process of economic growth driven by agricultural modernization. Important transformations of soil occupation can be observed, and water resource exploitation is often disorganised and predatory. The karst aquifers on the San Franciscan depression are located downstream of an intensively exploited region, the Urucuia sandstone aquifer. Karst aquifers are characterised by high vulnerability to contamination and low capacity of self-purification. This study aims to: (i) perform a preliminary characterization of the hydrogeological behaviour of the karst system in relation with the whole basin context by characterising water hydrochemistry, and (ii) to verify the existence of anthropogenic pollution in order to delineate the aquifer vulnerability. The first results showed a great heterogeneity of aquifer waters, denoted by water chemistry. This heterogeneity was not only related to a large basin surface and different recharge conditions, but also to aquifer compartmentalisation in depth. Results denoted the possible existence of redox processes associated to organic deposits in depth.