عنوان مقاله [English]
Water quality, as its quantity, is one of the most important determinant factors for its application in various uses. Physical and chemical properties of water play an important role in categorizing and evaluating water quality. With the aim of detecting the water chemical quality of Gupal river in the south of the country and studying its annual changes during the years 1982 to 2011, its physical and chemical parameters were studied. Since the presentation of the results of water quality analysis in the graphical form simplifies and makes faster understanding of complexity of surface water systems, graphical methods such as Wilcox, Schuler, Piper and Collins diagrams were also used. The results of variation and trends analysis of water quality parameters showed that in spite of the decreasing in the trend of acidity and flow rates, other chemical parameters of water had an increase in their trend and their terms was in order of 5, 10, 20 and 30, respectively. Increasing in the trend of variation in the water quality parameters and dissolved salts indicates a decrease in water quality and an increase in dissolved salts. The Wilcox diagram showed that the water lied in the class of C4S3and was inappropriate for irrigation and agricultural uses, and Schuler’s diagram showed the water quality is not acceptable and in terms of industrial water consumption the river was precipitate and the Piper diagram showed that the dominant ions in this river are sodium and sulfate, and water has type and facies of sulfate sodic.