عنوان مقاله [English]
The Kan River is one of the branches of the karaj River and the largest and most important river that enters the Tehran plain. The water quality of a part of this river in the urban section (Tehran city), is affected by agricultural and industrial activities and population spots. The aim of this study was to investigate the quality of the Kan River water quality using Iran Water Quality Index for Surface Water to protect the environment. After data collection and field visits, the study area was divided into eight longitudinal range (zones A to H) and then sampling stations (9 stations) were selected. After of selecting the stations, sampling was done in two periods of minimum and maximum flow of river water. Based on Iran Water Quality Index for Surface Water, Kan River is of poor to relatively bad quality. According to the analysis of water quality of Kan River and Comparing the parameters using Iran Water Quality Standards, the pH level was in standard level but some parameters such as, BOD (Biological Oxigen Demand) in 2 stations in minimum flow rate and 9 stations in maximum flow rate and TSS (Total Suspended Solids) in 4 stations in minimum flow rate and 5 stations in maximum flow rate were more than permissible level of national standard for river water quality. DO (Disolved Oxigen) in all samples except station S1(upstream of Kan River) in minimum flow rate and Coliform in all samples in minimum and maximum flow rate of the Kan River were more than permissible level of national standard for river water quality. Due to these analysis, man-made sources such as entering industrial, municipal and agricultural wastewater are the most important reasons for decreas of river water quality. In terms of standard classification base of the Iran Departement of Environment for Protection of aquatic life, class 2 (suitable for Cyprinidae (is recommended.
The tributaries of the Kan River are pollution-free and the trend of increasing pollution from upstream to downstream is evident. The most polluted waterway is the flood reversal route of the west, and the water quality of the Kan River becomes very poor after receiving it .Because the quality of Kan River is affected by urban, industrial and agricultural pollutants, due to increase of population, industrial and agricultural development and increasing use of pesticides and fertilisers; it is also necessary to carry out qualitative conservation measures and control the pollutant factors. Finally, in order to protect the environment of urban rivers, it is suggested that some measures are determined such as complete documentation of hazards (type of hazard, meteorological and water quality data, location, images and films of damages, etc.), determination of return period against flood hazards, no groundwater abstraction without obtaining a license from the Tehran Regional Water Company. It is also recommended to set a special program for the protection of existing species in the Kan River catchment that are in danger of extinction or reduction for more protection of the river ecosystems and environment. Not using artificial structures for shallow and sloping water canals along the river and even the possibility of using rocks and Natural materials for natural regeneration is also recommended. At the end, the most important suggestion is to setting stricter standards for the discharge of sewage and effluent into urban rivers.