One of the fundamental problems of sustainable development in a country is the lack of water resources in terms of quantity and quality. The Dargaz aquifer (DA) is located in the north of Khorasan Razavi province near the border of Iran and Turkmenistan. In this paper, an attempt has been made to investigate the hydrogeochemical evolution of water resources in the Dargaz plain using hydrogeochemical techniques. The results show that the quality of groundwater decreases in flow direction from west to east. In addition to natural factors (dissolution of Tirgan and Sarcheshmeh formations), human factors are also involved in the water quality of the studied area. According to the Piper diagram, the dominant type of water in the region is sodium-calcium sulfate. The groundwater quality is acceptable for drinking and agricultural purposes, and it is hard to completely hard water for industrial purposes.

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