Groundwater quality and hydrogeochemical challenges in the Sarakhs Plain, NE Iran: a call for sustainable management

The physicochemical analysis of 292 groundwater samples from the Sarakhs Plain revealed significant variations in water quality, influenced by natural factors. The pH values ranged from 6.4 to 8.6, with an average of 7.97, indicating that most of the samples (98.97%) meet WHO drinking water standards. However, electrical conductivity (EC) levels were alarmingly high, ranging from 1020 to 37,500 μS cm^-1, making all samples unsuitable for drinking. Ca²⁺ and Mg²⁺ concentrations were within acceptable limits for approximately 88.39% and 61.09% of the samples, respectively. Spatial distribution analysis showed that higher salinity levels were concentrated in the western and central regions, while the eastern areas benefited from fresher water due to the influence of the Harirud River, which enhances groundwater quality through natural dilution processes. Hydrogeochemical assessments indicated a predominance of mixed-type water, with significant intrusion processes affecting chemical composition. The Gibbs diagram highlighted evaporation as a major factor influencing water chemistry. Groundwater quality index (GWQI) indicated that nearly half of the samples were classified as unsuitable for drinking, while agricultural suitability varied significantly. Although salinity was a critical concern, many samples were deemed suitable for irrigation based on specific ion concentrations. Overall, this study addressed the necessity for sustainable groundwater management practices in the Sarakhs Plain to mitigate salinity issues and enhance water quality for both human consumption and agricultural use.