long-term (1969-2013) changes of water parameters in neka and tajan rivers, mazandaran, iran

Background: iran is located in the global arid zone. with an average rainfall of less than 250 mm. 25 percent is iran of located in hyperdry area and 40 percent in the arid area. in 2007, the world bank report declared the annual reduction of freshwater resources in iran 6 times more than global standards and indicators. since at present, in iran most available fresh water enters the water ecosystems, their management is vitally important due to climate changes and water quality parameters. methods: in this study, long term changes of some parameters including hardness, dissolved solids and ec, ph, hco3, ca, na, mg, cl and so4 were investigated for a period of 44 years in two key rivers (neka and tajan rivers) in the north of iran.results: the results show that there was the same changes pattern in all parameters in both rivers. the highest level of correlation was between electrical conductivity and dissolved solids in both rivers. also, due to the similarity of the hydrological characteristics of the rivers, the impact of area development by local people is playing a major role in the environmental health.conclusion: although iran's northern regions have high rate of precipitation, status of water quality parameters is an indicator of low levels of water quality and its pollution.