A systemic approach to address eutrophication and water management in the Río Grande de Comitán-Lagos de Montebello watershed, Mexico

Anthropogenic eutrophication is a prevalent issue that impacts water quality by excessive nutrient loads, primarily of nitrogen and phosphorus. This study examines the causes and impacts of nutrient enrichment and its spatial–temporal variability across the Río Grande de Comitán-Lagos de Montebello watershed (RGC-LM, Mexico). We applied a mixed-methods design that integrates seasonal water quality field measurements of physicochemical parameters and nutrients, and qualitative information from interviews with local stakeholders within a systemic Driver–Pressure–State–Impact–Response (DPSIR) framework. Nutrient accumulation in this watershed is characterised by the combined influence of diffuse and point-source pollution, hydrological connectivity, and socio-institutional factors. Untreated wastewater discharges dominate nutrient inputs in the upper watershed and agricultural runoff constitutes the main diffuse source in the middle watershed. These pressures propagate downstream and differentially affect mountain and plateau lakes in the Lagunas de Montebello National Park (LMNP), a wetland of international importance. Our findings reveal complex challenges in eutrophication management and underscore the need for localised and feasible strategies tailored to the conditions of the watershed. We propose region-specific responses that combine wastewater management, nature-based solutions, legal actions, remote sensing and community-based monitoring to support national water policy and Ramsar commitments in a complex socio-ecological system.