Environmental Assessment of River Water Quality in Sarough Watershed Using an Integrated Physicochemical Approach

Reduction of river water quality has negative effects on aquatic organisms and agricultural activities and threats public health in surrounding areas. So, monitoring of river water quality is used to determine suitability of water for drinking and irrigation uses. This study investigated the hydrogeochemistry and water quality of rivers in Sarough watershed using the major ion chemistry and explores multivariate statistical methods for identification of processes which release the solutes in natural waters. Totally, 38 samples were collected along the main rivers of studied watershed. The concentrations of major cations (Na+, K+, Mg2+, Ca2+) and anions (Cl-, NO3 -, HCO3 -, CO3 -, SO4 -2) were determined. The results indicated that the river water is neutral and fresh in nature. The most of samples are categorized in hard and very hard water class and are under-saturated regarding with calcite and dolomite. The major water types are Ca–HCO3–SO4, Ca–Mg–CO3 and Ca–SO4–HCO3. The results of multivariate statistical techniques (CA, PCA and correlation coefficient matrix) indicated the strong association between Na-Cl-SO4-K and Ca-Mg-CO3-TH. It is assumed that dissolution of carbonate minerals such as calcite and dolomite is the dominant hydrogeochemical process which releases the major ions into the watershed, but cation exchange processes such as silicate and clay mineral weathering and soil-salt leaching also play an important role. The result is consistent with the lithological distribution of the area which shows that carbonate rocks and gypsiferous marl formations are widespread in the watersheds. Also, it is assumed that travertine springs release the elements especially Ca, Mg and CO3 into the drainage system. The Na+, Cl- and NO3 - concentration in all water samples falls within the accepted limit for drinking (WHO ISIRI 1053). Nevertheless, Ca2+, Mg2+ and SO4 2- content in some collected samples are higher than the maximum desirable limits. Schuler graph shows that majority of samples are good and acceptable for drinking. Evaluating the quality of river water for irrigation purposes using Wilcox diagram and SAR, EC and RSC index results indicated that majority of the samples are suitable for irrigation.