Application of water quality index (WQI) and hydro-geochemistry for surface water quality assessment, Chahnimeh reservoirs in the Sistan and Baluchestan Province

Chahnimeh water reservoirs in Sistan and Baluchestan Province are the most important sources for drinking water and irrigation purposes. Many factors such as precipitation, the geography of the watershed, atmosphere, geology and Human activities affect on the chemical, physical, and biological compositions of Chahnimeh water reservoirs. Therefore, the main goal of the present study was to monitor and assess water quality in four Chahnimeh reservoirs during two sampling periods. 84 water samples were taken based on the standard methods (in September 2017 and April 2018) for measurement of the most important physicochemical parameters including major anions, total coliform, BOD, EC, TDS, pH and nitrate. Water quality index (WQI) was used to evaluate the overall water quality status in the Chahnimeh reservoirs. The results of hydro-geochemical analysis indicated that the water type changed from sodic bicarbonate and sulfur dioxide to radicle chloride during sampling periods. The Gibbs chart showed that weathering of rocks mainly controlled the chemistry of the main water ions. The results of statistical analyses revealed that there was a high correlation between parameters such as chlorophyll, nitrate, sulfate and chlorine with water quality index. Water quality zoning results based on the WQI index indicated a decrease in the water quality of the wells by 3, 2, 1, and 4, respectively. In this study, the use of WQI was helpful for fast data interpretation for drinking water purposes in the area. Based on the WQI classification, majority of the samples are falling under good to poor water category.