Identification of the components of a complex groundwater flow system subjected to intensive exploitation

• Published in: Journal of South American earth sciences Vol. 98; p. 102434
• Main Authors: Olea-Olea, Selene, Escolero, Oscar, Mahlknecht, Jürgen, Ortega, Lucia, Silva-Aguilera, Raúl, Florez-Peñaloza, Jose Roberto, Perez-Quezadas, Juan, Zamora-Martinez, Olivia
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2020
• Subjects: End-members mixing analysis; Groundwater chemistry; Groundwater flow system; Groundwater intensive exploitation; Structural geology; Groundwater intensive exploitation; End-members mixing analysis; Structural geology; Groundwater chemistry; Groundwater flow system
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2019.102434

The Mexico City region, like many other densely populated regions in the world, has problems in guaranteeing the supply of drinking water to its inhabitants. Its groundwater flow system is subject to intensive exploitation. To ensure proper water management, it is important to understand the behavior of groundwater flow system components under conditions of intensive exploitation. In this study, we analyzed 169 samples from drinking water supply wells, according to their chemistry. The principal components of the flow system were inferred using exploratory statistical analysis and analysis of the mixture of the end-members of the hydrochemical dataset. Four components were identified: (1) waters of recent infiltration and local circulation, (2) waters with evidence of intermediate chemical evolution, (3) waters that are chemically more evolved and of large flow trajectories, (4) waters that are chemically more evolved and of deep circulation. A relationship between the components, the structural geology, and the recharge zones was established. The mixing proportion of the four components in each water sample extracted from drinking water wells was identified. It was observed that the faults and the design of screened section of the well tubes influenced the mixtures captured by the wells. The impact generated by the intensive exploitation with respect to the distribution of the components within the flow system was evaluated. •The groundwater flow system was modified during the past decades.•Four flow components were identified: one local, one intermediate and two regional.•Silicate weathering and ion exchange are the most relevant water-rock interactions.•Wells have mixtures of two or more flow components related to construction design.