Methodology for defining a groundwater geochemical baseline integrating flow system theory: A case study in southern Mexico

Abstract

The concept of baseline is crucial for assessing natural water conditions and detecting anthropogenic influences in groundwater systems. This research proposes a methodology to define a geochemical baseline using the groundwater flow theory to develop a conceptual model, distinct from most methodologies that primarily rely on statistical techniques. The proposed methodology comprises three phases: defining a conceptual model, defining a geochemical baseline based on hydrogeochemical characterization, and identifying anthropogenic sources. This approach enhances understanding of hydrogeologic processes such as water-rock interactions, exchanges with other water bodies, redox conditions, and groundwater flow by integrating information about geology, structural geology, base level of discharge, hydrological connectivity, topography, and water table. The methodology was applied in the southern region of Mexico, specifically in the Comitán-Montebello lakes watershed characterized by complex features like the karst system and interactions with surface water bodies, providing relevant insights into the hydrogeological setting. It is a cost-effective approach that improves understanding of hydrogeological processes in data-scarce areas, thereby supporting the establishment of geochemical baselines.