Nitrate behavior in a groundwater flow system that discharges into the largest lakes of Mexico

The nitrate input in the groundwater and surface water is the main source of contamination in many areas of the world. In Mexico, agricultural activities depending of groundwater and surface water. The groundwater flow system (GFS) is a single system with recharge and discharge zone were the interactions between surface and groundwater are present. In Mexico, the Cuitzeo GFS is a is one of the most agriculturally developed areas in central Mexico and includes the second and third largest lakes, lakes Cuitzeo and Patzcuaro.
The main object of this work is to analyze the nitrate behavior in groundwater and lake waters to understand the spatial changes over two years.
The methodology includes sampling of major ions of 39 sites, including wells, dugwells, springs, and lakes in the dry season for the years 2024 and 2025. Additionally, hydrogeochemical diagrams and spatial analysis were developed. The nitrate concentrations in this country are regulated by Mexican rules.
The results show that 11 sites exceed the permitted limit of concentrations according to these rules. Nitrates predominate in the zone of major population close to Morelia city and close to Lake Cuitzeo. Whereas ammonium is present close to the lake Patzcuaro. These distributions are in groundwater and surface waters, reflecting the same processes in both water bodies. This area presents a rapid expansion and intensification of berry and avocado cultivation, which have displaced local crops and driven unsustainable patterns of agricultural water use.
This study provided valuable information about the source and quantification of nitrate species contaminations, which can help to generate new management strategies.