Hydrochemistry, δD and δ18O to explain the distribution of water quality in a karst setting in the semi-arid region of Northeast Mexico

Characterization of the groundwater flow systems can be used in conjunction with the geochemical evolution of groundwater to assess water-rock interaction processes, time of residence, and the regional hydrogeochemical evolution system. To identify the regime of groundwater flow, we consider it is essential to localize the geographic components of the hydrologic cycle, where the geologic environment determines the functional areas such as the recharge and discharge areas and the dynamics of water availability of the aquifer, as well as water quality. In this paper, we analyzed the groundwater flow systems on a section of chalky rocks, known as Plataforma Valle-San Luis Potosi (PVSL), located in the state of Tamaulipas, Northeast Mexico. The groundwater from the study area has dissolved Ca2+ and HCO3- as dominant ions; average concentrations are 118.9 and 253.9 mg/L, respectively. Thought to be derived from calcite dissolution, basically under the influence of the massif of the Sierra Madre Oriental, a karst Quaternary environment denominated El Abra Formation, a sedimentary rocks geology that dominates the regional geology. We used the cluster analysis to classify the primary element concentrations in two groups and three subgroups, where we could identify a local, intermediate, and regional flow. Defining the evolution of groundwater from recent waters on Ca2+ to HCO3- and dominance of SO4-2 to waters with more residence period, associated with the dissolution of gypsum from the Guaxcama Formation. That's was corroborate by utilization of delta D and delta 18O data which allow the identification of the recharge areas with mean values from - 7.94 delta 18O (parts per thousand) and 53.84 delta D (parts per thousand) on recharge areas, and - 8.19 parts per thousand delta O-18 and 57.83 parts per thousand delta D on intermediate flow. This result contributes to describe the geochemical process of groundwater and how it interacts with geological formations with El Abra Formation, the most crucial geological-water unity for the study area.

Automated summary

Characterization of groundwater flow systems, combined with geochemical evolution, helps assess water-rock interactions and regional hydrogeochemical evolution. Analyzing the geological environment and dynamics of water sources is crucial in identifying groundwater flow patterns. Cluster analysis was used to classify primary element concentrations, distinguishing local, intermediate, and regional groundwater flow, shedding light on the geochemical processes of groundwater and its interaction with geological formations.