water quality evaluation of torghabeh river of mashhad using combination of nsfwqi index and geographic information system

objective: mashhad metropolis as the second largest religioncity in the world and the second largest metropolis of iran with an annual 3 million pilgrims have significant direct and indirect effects on the watershed leading to the city and surrounding over the past four decades. there is no collection system and sanitation disposal network in towns and villages within the torghabeh river.  methods: therefore, in this study the qualitative changes of torghabeh river from october 2011 to september 2012 at 8 stations during four seasons (autumn, winter, spring, summer) was investigated by sampling of surface waters and measurement of water quality parameters along the river. data from this study were analyzed using nsfwqi index and finally was zoning using gis software. results: the results showed that the best and worst quality is related to stations 1 and 8, respectively. moreover, it was found that the autumn season with an average of 46 has the best quality among the studied seasons. however, the worst situation (bad quality) was related to winter season with an average of 39. finally, it can be concluded that the water quality of torghabeh river in its different parts is far from the desired level.