Hydrochemical Indicator Analysis of Seawater Intrusion into Coastal Aquifers of Semiarid Areas

Jobst Wurl (), Miguel Angel Imaz-Lamadrid, Lía Celina Mendez-Rodriguez and Pablo Hernández-Morales
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Jobst Wurl: Departamento Académico de Ciencias de la Tierra, Universidad Autónoma de Baja California Sur, Carretera al Sur km 5.5, La Paz 23080, Mexico
Miguel Angel Imaz-Lamadrid: Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Carretera al Sur km 5.5, La Paz 23080, Mexico
Lía Celina Mendez-Rodriguez: Centro de Investigaciones Biológicas del Noroeste S.C (CIBNOR), Calle IPN 195, La Paz 23096, Mexico
Pablo Hernández-Morales: Departamento Académico de Ciencias Marinas y Costeras, Universidad Autónoma de Baja California Sur, Carretera al Sur km 5.5, La Paz 23080, Mexico

Resources, 2023, vol. 12, issue 4, 1-25

Abstract: Saltwater intrusion into groundwater systems is a problem worldwide and is induced mainly by human activities, such as groundwater overexploitation and climate change. The coastal Los Planes aquifer in the southern part of the Baja California Peninsula (Mexico) is affected by seawater intrusion due to more than 40 years of groundwater overexploitation. A dataset of 55 samples was compiled, including 18 samples from our campaigns between 2014 and 2016. Several methods exist to define the impact of seawater in a coastal aquifer, such as the “seawater fraction”, the “Chloro-Alkaline Indices”, the “Hydrochemical Facies Evolution Diagram”, and the “Saltwater Mixing Index”. These methods provide reasonable results for most of the coastal zone of the Los Planes aquifer. A slight increase in mineralization was observed from 2014 to 2016 compared with the situation in 2003. However, in its northwestern part, samples from hydrothermal wells were not recognized by these methods. Here, the aquifer is affected mainly by thermal water with elevated mineralization, introduced through the El Sargento fault, a main fault, which cuts through the study area in the north–south direction. By considering known hydrothermal manifestations in the interpretation, samples could be classified as a combination of four end-members: fresh groundwater, seawater, and the composition of two types of thermal water. One thermal endmember with very low mineralization coincides with the thermal water described from the Los Cabos Block, where meteoric water represents the source (found in the Sierra la Laguna). The second endmember is comparable to coastal thermal manifestations where seawater represents the main source. Therefore, the higher mineralization in the northwestern zone is the result of the mobilization of thermal groundwater and direct mixing with seawater, which is introduced locally at the coast due to overextraction. This finding is important for future management strategies of the aquifer.

Keywords: hydrogeochemical characterization; seawater intrusion processes; geothermal water; mixing processes; cation exchange; Los Cabos block (search for similar items in EconPapers)
JEL-codes: Q1 Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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