Origin of the Salinity in the Coastal Aquifer of La Paz, Mexico

Abstract

Coastal areas are attractive places for the establishment of urban settlements owing to the many benefits in terms of quality of life. An example of these areas is La Paz in Southern Baja California, Mexico, where demographic growth and agricultural activities under dry climatic conditions are threatening the availability of water resources. In recent years, an increasing salinity of groundwater has been identified, however, the origin of the salinity is not clear. Near the coastline, salt water intrusion is considered to be the main factor, while others play a role for increased salinities in the middle and upper aquifer zone. The study, using a hydrochemical tool analysis shows that the salinity of the coastline is the result of over-exploitation of wells, which increases saline intrusion resulting in a reverse cation exchange. It also indicates that the salinization of water in the recharge area is product of carbon dioxide dissolution and weathering of rock-forming silicate minerals, and in the central part result from cycling and use of fertilizer in agriculture.