Chemical Quality Survey and Trends of Water Quality Parameters at Nodeh Station of Gorganroud River, Golestan Province of Iran

Rivers are important because they are one of the major sources of water supply for various uses including agriculture, industry and drinking. Considering to importance of this tract and droughts in recent years, protect of these resources is very important. In this study, to survey the chemical quality and trend of water quality parameters was used 37 years of data for Golestan Gorganrood River in Nodeh station that these data are belong to this station. For this purpose, the river's water quality condition is determined using graphics method and annual general trend and different season of the years are specified and determined. Considering to this fact that all observed series were abnormal, we used from nonparametric test of man - Kendall to determine the trends of data. The results of Qualitative analysis showed that considering to Piper diagram of water, Gorganroud river is one of the brackish water types and the base of total hardness, is from hard type. According to the Schuler chart, this region is in acceptable range from aspect of drinking water and the Vylkvks graph results showed that it is can be used for agriculture. The results of trend showed that the most significant parameters in Nodeh station have been rising and significant trend in long-term. In general, considering declining trend of flow discharge in different seasons of year and rising trend of existing salinity in the water, will cause reduction the chemical quality of water for various uses.