assessment of surface water quality in the vanak-soolegan basin, western iran

As monitoring and assessment of water quality are assumed as important factors in the improvement of the communities’ sanitary status the in 21st century, optimal management of freshwater resources should be taken as an integral part of d. evelopment programs worldwide. the main objective of the current study was, therefore, to assess the characteristics of surface water quality in the vanak-soolegan basin and to identify its long-term trend of variations, using graphical methods. to this end, the required data were collected from three hydrometric stations (soolegan, tagarg-ab, and tange zardaloo). then, for a better understanding of water quality, the data were analyzed based on 11 different parameters including electrical conductivity (ec), total dissolved solids (tds), acidity (ph), calcium (ca), magnesium (mg), sodium (na), potassium (k), bicarbonate (hco3), carbonate (co3), chlorine (cl) and sulphate (so4). assessment of water quality was also performed by drawing schoeller, piper and wilcox diagrams. as revealed by the piper diagram, the dominant water type was calcium-bicarbonate. the results of the schoeller-diagram demonstration showed that the water samples fell in potable and acceptable class and that based on the wilcox diagram, the majority of samples were classified into low salinity class (c2s1) which is suitable for farming. moreover, the trend analysis of selected parameters was performed via the mann–kendall test on a 18-year period (from 1995 to 2012). the results indicated a positive trend in ec, t.d.s, ca, k, and so4 at the soolegan and tagarg-ab stations. in general, it seems that several factors are involved in water quality changes including the weathering of the hard rocks, lithology, drought, and increase in water consumption.