Pages: 13-22

Abstract

The purpose of this study is to provide an accurate picture of the status of surface water quality to identify the amount of its pollution with contaminating substances so that the adoption of appropriate management practices for protecting water resources of the country at any point is determined. The objective of this study is microbial contamination of the Bahmanshir River based on water quality index in GIS environment. The method used in this study is quantitative-analytical, and to identify the impact of municipal, industrial, and agricultural wastewater and residential centers from the water outlet of the Bahmanshir River in 10 different stations, a study was conducted. River water quality parameters (fecal coliform, temperature, turbidity, PH, DO, BOD, nitrate, phosphate, Ts) in the summer and fall of 2015, in August and November in 10 to 20 of each month and three times- 6 am, 12 noon and 6 pm- were studied and evaluated. Sampling, preparation, and analysis of samples were done according to standard methods (Standard Method, 1998).. Investigation showed that monthly water quality index of the river during the study period is variable in range of 22_36 and is in poor to very poor group. Water Quality Index (WQI) gradually reduces from the first station to the last station. Station 5 on the Karun River and entry of the Bahmanshir with index 22 in summer has the worst and stations 2 and 3 on the Mard Canal upstream with an index of 36 in the fall have the best status. In upstream stations of the Mard Canal, due to lack of overflow of urban, hospital, and factory sewage, the index has high quality range. In downstream station like stations 5 and 8 due to the arrival of hospital wastewater, the status of riverbank bed has changed, WQI is low, and in station 9 due to the entry of the aggregate of urban wastewater, the lowest quality index was recorded. Studying water quality in autumn and summer showed that autumn has the best status due to the start of rainfall and reduction of the pollutants, and summer has the worst status due to lack of rainfall, high temperature and evaporation, increase in wastewater, suitable conditions for coliforms growth, and increased opacity.