Analysis of isoscapes (δD, δ¹⁸O and tritium) in groundwater in the semiarid northeast region of Mexico

Arid and semiarid zones often lack surface water sources. Since aquifers are the only source of water supply in these zones, they are at risk of overexploitation. In understanding the behavior and dynamics of aquifers within the hydrological cycle, isotope hydrology is a useful tool. The objective of this study was to develop a conceptual hydrogeological model in the arid zone associated with the Tula-Bustamante aquifer, Mexico. Stable deuterium (δD), oxygen-18 (δ¹⁸O) and tritium isotopes were used to investigate the hydrogeological processes and dynamics in the aquifer to identify the recharge zones and the origin and residence time of groundwater. Precipitation data for the region indicate that the study area went through a dry season, with 2017 being the year with the least rainfall in the 20-year study period. The analysis of the δD and δ¹⁸O groundwater isoscapes (maps of values) for 2016 and 2017 show that the main aquifer recharge zone is in the eastern part, in the mountainous area of the Sierra Madre Oriental. Tritium distribution indicates that the region has mixed and premodern waters. In addition, hydrological analyses results, in conjunction with the stable isotope values obtained, suggest a fast hydrological flow. The results of this research made it possible to generate a suitable hydrogeological model of the aquifer, which can be used as a groundwater resource management tool to prevent overexploitation.