Comparison of Physical and Chemical Characteristics of Rivers` Water in North Tehran

The rivers in the north of Tehran that are permanent, from east to west include Darabad, Darband, Derkeh, Chin-Kalagh, Farahzad and Kan rivers. In this study the hydrochemical properties of the northern rivers of Tehran to the point of entry into the city and the impact of natural factors such as geological formations and human factors on water quality characteristics has been evaluated. In order to determine the possible source and processes affecting river water quality, mineral saturation index, ion ratios and dispersion diagrams were used. Hence, the water quality of rivers in the north of Tehran upstream is mostly controlled by dissolution and weathering processes and at the outlet is affected by urban activities. The rate of microbial contamination in all rivers is lower in winter than in other seasons. Finally, the diagrams show that the water quality of the north of Tehran rivers upstream are mainly influenced by natural factors and geological formations, and at downstream parts the water quality is mostly controlled by human activities and urban pollution. These rivers mostly are of good quality before reaching recreation centers of north of Tehran city.