Critically Assessment of Groundwater Quality Based on WQI and Its Vulnerability to Saltwater Intrusion in a Coastal City, Iran

Groundwater pollution, thereupon, has be-come an acute problem that if thrust aside will escalate to a point of no return. The purpose of this paper was to assess the quality of groundwater in Behshahr (Iran) based on water quality index (WQI). Sixteen water samples from this coastal aquifer were collected and analyzed to study physico-chemical parameters such as pH, hardness, chloride (Cl), electrical conductivity (EC) and total dissolved solids (TDS). The results showed that the annual average of TDS value increased by 343 mg/l between 1999 and 2015 due to anthropogenic activities. According to WQI, it was concluded that the groundwater quality degraded over the last sixteen-year period so that the percentage of samples identified as “good water” decreased by 18.5% and on the other hand, alas, the percentage of “poor water” quality soared by nearly 12.5%. Correspondence of WQI distribution diagram with that of chloride-bicarbonate ratio attests to the significant contribution of saltwater intrusion to groundwater quality deterioration in this area. This simple yet precise method presents a comprehensive interpretation of water quality in a basin. Its sensitivity to chloride that has high weight makes it a good measure for seeking out the threshold of saltwater intrusion in this study area.