Changes in the residence time of a spring in a tectonic active zone of central Mexico

The residence time of a spring located in central Mexico has been affected by seismic activity. The region is influenced by the interaction of five tectonic plates - Cocos, North American, Pacific, Rivera, and Caribbean - with convergent, divergent, and transform boundaries, leading to frequent earthquakes.

The spring, known as the name “Agua Hedionda”, has therapeutic properties due to sulfate concentrations exceeding 1 g/L that contributes significantly to the local economy. However, the earthquake of magnitude 7.1 in 2017 had a substantial impact, particularly on the flow quantity and sulfate concentrations, evidencing the vulnerability of the spring and, consequently, the community's economy.

To comprehend the vulnerability and changes in the spring, data of tracers (O-18, H-2, H-3, C-14), major ions and flow measurements were collected in 2022.Then, these data were compared with pre- and post-earthquake information.

Tracers facilitated the estimation of residence time for water reaching the spring, indicating a regional flow after the earthquake and an intermediate flow before and currently. The chemical and isotopic data suggest a mixing of flows.

Tectonic movements imply that the spring received water with a longer residence time compared to its original state. The combined analysis of these data in tectonically active areas offers valuable insights into changes in residence times, thereby understanding variations and the vulnerability of groundwater resources.