Adapting the EPIK method to Brazilian Hydro(geo)logical context of the São Miguel watershed to assess karstic aquifer vulnerability to contamination

Abstract

Karst aquifers are, besides important strategic reservoirs of good quality water, heterogeneous and anisotropic, where highly permeable karst networks result in insufficient time for contaminant degradations, and hence the quasi-immediate contamination of the aquifer. The EPIK method is a low-cost technique and was developed to map karst regions based on four main feature indexes: 1) epikarst; 2) protective cover; 3) infiltration conditions; and 4) karst network development. However, the method was developed according to European hydrogeologic and temperate climatic contexts, where its application without adaptations in regions in different contexts may result in possible misunderstandings, such as overlook, underestimate or overestimate significances of some parameters (e.g. soil covers, rainfall regimes, morphological domains). The Brazilian São Miguel watershed, a tropical karst region where the city of Pains is located (southwestern Minas Gerais), is characterized by high levels of thermotolerant coliforms, phosphorus, nitrate, and cadmium in surface water and groundwater. These contaminants come from, agriculture, livestock, and urban areas. Due to these issues and to provide a tool of water resource management and land use planning, the EPIK method was adapted to the hydrogeologic reality of the São Miguel watershed, considering both local vegetation and the current Brazilian speleological heritage protection legislation. Results revealed that 52% of the area has moderate vulnerability and 7% high vulnerability, this latter one concentrated in areas close to mining activities and urban areas. The study provided a reliable map and adapted technique which can be used in other Brazilian karst regions and other tropical karst regions.