Hydrochemistry and quality assessment of Derbendikhan Reservoir, Kurdistan Region, Northeastern Iraq

Abstract

Derbendikhan Reservoir is located 60 km southeast of Sulaimani City in Kurdistan Region, northeastern Iraq. Water hydrochemistry of Derbendikhan Reservoir is examined to assess its quality and the effect of human activities such as waste disposal, agricultural uses, and industrial pollution. Forty-four water samples were collected and investigated using standard methods. Sampling was conducted during low- and high-flow periods (LFP and HFP). The studies included physicochemical variables such as electrical conductivity (EC), temperature, total dissolved solids (TDS), salinity, and pH. The water of HFP was more alkaline (pH 8.5) than that of LFP (pH 7.7). The EC was Mg2+ (13, 10.9) > Na+ (10, 9.0) > K+ (2.5, 2) and HCO3− (129, 112) > SO42− (66, 46.3) > Cl− (13, 8.1) > NO3− (0.37, 3.21). Physicochemical parameters showed slightly higher values of HFP than LFP. All of these variables were within the drinking water quality standards of the World Health Organization. The overall results of sodium adsorption ratio (SAR) and salinity hazard showed that the studied water is clean for drinking and irrigation purposes. Piper, Schoeller, and Gibbs diagrams were used to assess the water characteristics which showed that they are Ca-bicarbonate, and relatively enriched in Mg2+ and SO42− during HFP and LFP. These imply that the waters of Derbendikhan Reservoir were originated from the chemically weathered carbonate- and gypsum-dominated rocks covering the drainage basin in the area. The hydrochemical studies also indicated that Tanjero and Sirwan rivers feeding Derbendikhan Reservoir has no significant polluting effect on these waters. The significant positive correlation suggests that the leading cations come from all kinds of bicarbonates and sulfates. Most of the physicochemical characteristics of water showed slight decrease with time.