Comprehensive integrated index–based geochemistry and hydrochemical analyses of groundwater resources for multiple consumptions under coastal conditions

The primary objective of this study was to assess the quality of groundwater in the Guilan aquifer, a principal aquifer in the north of Iran, for drinking, irrigation, and industrial purposes. In this regard, groundwater samples have taken from a database provided by the Water Resources Authority of Guilan Province, Iran's Ministry of Energy. The studied four main regions of this aquifer were Talesh, Astaneh, Lahijan, and Foomenat. Achieved results were compared with the maximum permissible limit values recommended by the World Health Organization (WHO) and Food and Agriculture Organization (FAO) water standards for drinking and agricultural purposes, respectively. Moreover, evaluation of water suitability for industrial application was determined. According to the different indices, groundwater quality is suitable for irrigation purposes in all studied areas. A Piper diagram illustrated that the most dominant water type was Ca-HCO₃ in the all studied areas. This result also is consistent with results from the analysis of mineral saturation index. Accordingly, the result of water quality index (WQI) revealed that the groundwater in the Guilan aquifer could categorize from excellent to poor quality classes. However, the majority of water samples in Astaneh region mostly fall into the poor water class. The calculation of corrosiveness and scaling indices as Ryznar stability index (RSI) illustrated that a large number of the samples could be classified into aggressive and very aggressive categories. The results additionally showed that tendency to form scale based on Puckorius scaling index (PSI) was observed in some groundwater samples. Overall, the status of groundwater quality in Talesh region was noteworthy better than the other studied regions, while Astaneh region is more vulnerable with elevated contents of ions and physicochemical parameters.