Hydrogeochemical conceptual model of groundwater and quality degradation of water resources, the basic challenge of coastal aquifers

Abstract

Abstract The scarcity of data on the hydrogeochemistry of coastal aquifers near the south Caspian Sea justified the current study. The evaluation was conducted on the groundwater found in the Behshahr-Bandargaz coastal aquifer using classical integrated methods, statistical analyses, and GIS applications. The hydrochemical assessment included 48 groundwater samples from an area located between the Alborz mountains and the Caspian Sea. The study aimed to assess hydrochemical properties, salinity origin, and water suitability. Groundwater chemistry is influenced primarily by water-rock interactions, Saltwater infiltration, evaporation, and geological processes contributed to water quality degradation. Spatial distribution maps revealed that most hydrochemical elements increased towards the coast, indicating declining water quality northward. Nitrate distribution differed, suggesting human activities had less impact than saltwater intrusion due to excessive groundwater extraction. The hydrogeochemical model showed increased EC and decreased nitrate towards the coast. Groundwater suitability assessment indicated decreasing quality towards the northern parts. The water quality index (WQI) for drinking purposes was excellent in many areas. For agriculture, water quality varied from slightly salty in the south to very salty in the north. Industrial use would render a large part of the aquifer corrosive. The water quality is suitable for drinking in most parts of the aquifer, but it is less suitable for agriculture and industry. The findings from this study are valuable for devising sustainable strategies to manage and safeguard groundwater in the coastal regions, particularly in the vicinity of the Caspian Sea. Additionally, they can serve as a crucial resource for researchers worldwide.