Groundwater Flow System and Hydrogeochemical Evolution in Central Mexico's Major Lakes

This study investigated the groundwater dynamics within the Cuitzeo groundwater flow system, an area encompassing central Mexico's second and third largest lakes. We combined water level observations, structural geology, hydrogeochemical data, stable isotopes, with statistical analysis and mixing models to investigate groundwater flow dynamics and geochemical evolution in the system. Three distinct groundwater flow trajectory groups were identified: Local, Intermediate and Regional, each exhibiting unique hydrogeochemical characteristics. Local flow paths were characterised by recent recharge and limited geochemical alteration. Intermediate flow trajectories showed evidence of more evolved waters, often associated with faults and intensive groundwater extraction zones. Regional flows, linked to fault zones along the shoreline of Lake Cuitzeo, displayed higher contents of major ions, dissolved Sr²⁺, Li⁺ and higher water temperatures. The lakes reflected discharge from different groundwater sources. Lake Pátzcuaro is predominantly fed by local recharge, while Lake Cuitzeo receives a more complex mix of flow paths. Intensive groundwater extraction, especially during the dry season for avocado plantations, has significantly disrupted natural flow regimes and lowered groundwater and lake levels. Our findings highlight the importance of integrated water resource management that accounts for interactions between local, intermediate and regional groundwater flow systems. Our results are especially relevant for lake basins fed by groundwater, where informed management strategies are essential considering increasing water demand scenarios. Additionally, this study draws international attention to the environmental impacts of high-value crops like avocado farming on groundwater in arid and semi-arid peri-urban regions across the Americas.