chemical quality

Physical and Chemical studies indicate that hydrochemical facies of Ziarat River, one of the drinking water resource, are (Ca-Mg -HCO+2; Cl3 - HCO3 -Ca-Mg). According to hardness classification, water class of Gorgan's drinking water isvery hard. While, the total dissolved solid of Gorgan's drinking water is rock-dominance, according to Gibbs classification. Regarding the present physical standards of drinking waters, turbidity is one of the most important parameters of the rivers which are used for drinking water. A several year evaluation of Ziarat River showed that the turbidity this river has been between 185-2572, prior to entrance to WTPG. High fluctuation of Ziarat River turbidity is due to flood nature of this river, so that turbidity of water manifest higher amount in 1378 compared to the following years. Regarding intensive erosion and sedimentation in the Ziarat watershed, in order to decrease the turbidity of water as well as consumption of chemical catalyzes in the WTPG, managements of watershed and construction of several pre-depositional ponds for collection of sediments in entrance of Ziarat River to the WTPG are recommended.