Water quality evaluation and trend analysis in the Qareh Sou Basin, Iran

This study focused on water quality variables, trend analysis and time series of monthly versus yearly values of selected physicochemical water quality parameters at the Qareh Sou Basin in Golestan Province in Iran. For this purpose, six hydrometer stations were used for the sampling during 1991–2010. On the basis of these data, the water quality conditions of the basin were analyzed and trend of the following physicochemical parameters of pH, EC, total dissolved solids (TDS), discharge, chloride, sulfate, bicarbonate, sodium, potassium, calcium, and magnesium has been determined. The results suggest the presence of momentous trends in water quality in long term period. The pH rate has increased during over period but the discharge rate decreased. Trends of bicarbonate, sodium, potassium, and calcium, which, following TDS, have increased in the first decade and declined during the second decade. Magnesium and sulfate, similar to discharge have shown decreasing trend during the subjected period.