Hydrogeochemical evolution and water quality assessment of surface and groundwater resources: case study, Shirin Darreh dam basin (NE Iran)

In this study, drinking and irrigation water quality in Shirin Darreh dam basin (1750 km2), NE Iran, was assessed. Thirty-three surface water, groundwater, and the reservoir water samples were analyzed for physicochemical parameters, including pH, EC, Ca2+, Mg2+, Na+, K+, CO32−, HCO3−, SO42−, and Cl−, in laboratory of Water Company of North Khorasan. Hydrogeochemical approaches showed that water-rock interaction was the main mechanism controlling the water chemistry in the study area. The major type of the water samples were determined by Mg2+, Na+, Ca2+, SO42−, Cl−, and HCO3− ions mainly originating from the developed marl, shale, and limestone rocky units in the study area. The water flow direction was addressed as one of the effective parameters on the ion content in the surface waters. Based on saturation index, gypsum, and anhydrite were under-saturated in all the water samples, and calcite and aragonite were super-saturated in major part of the water samples. Drinking quality of the water samples was in suitable, intermediate, good and inappropriate categories, and thoroughly unpleasant and non-potable classes were not dominant based on Schoeller classification. According to water quality index, 36 and 64% of the water samples were in unsuitable and suitable drinking water quality ranges, respectively. Among the irrigation water quality indices, EC, MH, SO42−, and Cl− hazards were damaging for agricultural purposes. The lithological frame of the study basin with erosion sensitive rocks is an important natural factor controlling the water resources quality for different purposes, especially drinking and irrigation.