evaluation of karun river water quality status based on water quality index and involving gis environment

in recent years, the water quality of karun river, iran, has been affected by different pollutant loads such as agricultural drainages, municipal and industrial wastewaters.water quality index (wqi) and gis as an efficient tool can be used to provide necessary support for decisions of the management actions in this river and also capability of time series models can be beneficial for forecasting future changes. therefore this paper aims to evaluate the water quality of karun river, according to wqi and using gis and modelling water quality time series. in this research, monthly data including ph, temperature, do, bod, tds, po43-, no3-, turbidity and fecal coliform were analyzed during years 2008 to 2013. all the calculated indices were classified in medium class that means the river water can be used only by applying advanced treatment. spatio-temporal distribution of wqi values and non-significance of its fluctuations indicate balance between the pollutants input and self-purification capacity. modeling revealed adequate coefficients of determination of selected autoregressive models that vary between 0.69 and 0.85. also man-made conditions realized as the dominant factor affecting river water quality. according to the results, karun river water quality has increased slightly comparing to the past and after dez river junction, relatively high decrease in wqi occurred that can indicate dez river’s lower quality because of entering pollutant loads in dezful station downstream and calls for control measures on the river.