Qualitative and quantitative investigation of Dez River water from the reach of Dez Dam to meeting point of Karun using NSFWQI index

Abstract

Dez River is one of the main branches of big Karun River which passes mountainous regions of Lorestan province before entering Khuzestan province. This river passes northern and middle areas of Khuzestan plain and joins Karun River in a region named Band-e-Ghir. In order to determine and classify water quality of Dez River, 9 sampling stations were determined. Sampling was done in autumn and winter in 2010. Then, seasonal quality index of autumn and winter for each station was determined using water quality index system based on curves and tables of water quality index in America; then, different stations were classified along the river pathway. Physicochemical parameters of the river water such as DO, BOD5, PH, TDS, nitrogen, phosphorous, turbidity, temperature and coliform were measured and then were investigated using NSF and GIS. Classification of the study stations based on water quality index system NSF showed that in autumn, station (1) has the maximum amount of quality index and station (6) has its minimum. In winter also, station (1) has the maximum and station (7) has the minimum amount of quality index. Also comparison of BOD, COD, PH and turbidity in the entire study period with standards of World Health Organization (WHO) demonstrated that, BOD and PH of all stations are standard. Turbidity of stations 1, 2,3,8,9 was standards and the rest of stations were higher than standard value. By comparison of the results of this study with similar conducted studies on other rivers in various countries and inside Iran, it can be concluded that, mean water quality of this river is lower than Malaysia and the U.S. rivers. Also, comparison of this river water quality with Indian rivers showed that, water quality of Dez River is higher than some Indian rivers and is similar to some other rivers in this country. Also, comparison of this river water quality with Tajan River which is located inside Iran showed that, mean water quality of Dez River is lower than Tajan River in Mazandaran province.