Identifying groundwater end members by spatio-temporal isotopic and hydrogeochemical records

ABSTRACT

Intensive groundwater use has altered the local hydrological cycle within the Bajío Guanajuatense, Mexico. To improve the knowledge of this hydrogeological system and support water management in the area, groundwater end members were identified using multivariate statistical analysis. Pumped groundwater is composed of two well-mixed end members: (a) recent recharge, affected by a reuse cycle through irrigation where nitrate and chloride evolve and reach levels of 368 mg/L and greater than 100 mg/L, respectively, and (b) deep old groundwater. Mixing estimations show that most wells extract at least 70% of deep groundwater, and some of them extract more than 94%, posing a development and groundwater sustainability conundrum in the area.

KEYWORDS:

• Groundwater recharge
• hydrogen-2
• hydrogen-3
• hydrogeology
• isotope hydrology
• Mexico
• rainfall
• oxygen-18
• water management
• wells

Acknowledgements

We thank the Sistema de Agua Potable y Alcantarillado de León (SAPAL) and the Comisión Estatal de Agua de Guanajuato (CEA) for providing information. We thank María del Rocío Salas Ortega, for her support in the development of this research; Pedro Morales Puente, Edith Cienfuegos Alvarado and Francisco Otero Trujano of the Stable Isotopes Laboratory of the National Geochemistry and Mineralogy Laboratory (LANGEM), at the Instituto de Geología, UNAM and Maria Carolina Muños Torres of the Environmental Geochemistry Laboratory of the Centro de Geociencias, UNAM for the quality of data obtained. An anonymous reviewer is thanked for critically reading the manuscript and suggesting substantial improvements.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Partial funding was provided by the International Atomic Energy Agency through grants MEX8025 and MEX8026.