Evaluation of Golin River water quality in Kermanshah Province by using National Sanitation Foundation Water Quality Index (NSFWQI)

Water is one of the main factors in human life and, in addition to drinking, it plays an important role in other uses related to human life and nature. Among the water resources, rivers are more important because those water resources are considered as open systems and are therefore subject to change. The quality of these water resources is one of the most important characteristics that leads to sustainable development. One of the most practical and cost-effective methods to determine the ecological health of water and determine whether the quality of water has decreased with human activities is the biological study of these water resources. To achieve this result, the use of water quality index is very useful. In Iran, two indices (NSFWQI) and (IRWQISC) have been used. Due to tropical climate conditions of Golin region and increasing of water shortage in the past years, and also because of the construction of Zagros dam on the river which use for irrigation of agricultural lands, measuring the water quality of the Golin River is important. Therefore, to investigate the temporal changes of Golin river water quality, the present study was carried out at the station located downstream of Najargolin village during 4 different seasons and qualitative studies were performed on them based on the National Sanitation Foundation Water Quality Index. The Golin river Basin is located between 45° 60' and 45° 44' east longitude and 34°26' and 34°9' north latitude and 3450 meters above sea level. The parameters studied were DO, pH, BOD5, NO3-, PO43-, turbidity, water temperature and TDS. Sampling was done in four periods of spring, summer, autumn and winter during the years 2019-2020, based on the standard method. According to the obtained results, the value of DO in November with the value of 9.23 mg/L was the highest value and in July, with the value of 7.55 mg/L was in the lowest range. The highest values of the pH were observed during January and December and the lowest parameter observed in March. The highest amount of BOD5 was observed in June and the lowest in September, with values of 9.60 and 4.75 mg/L, respectively. In June, October, November, December, January and February, the BOD5 parameter showed higher values than other months. It was found that the highest value of NO3 was observed in April, November, December, January and February, respectively. The highest value of phosphate observed in June with a rate of 1 mg/L and the lowest amount was observed in November with a rate of 0.18 mg/L. The results of water turbidity in the river during the year showed that the highest value of this parameter was in November and the lowest were in January, July and September. According to results, dissolved oxygen (DO) with an annual average of 8.45 mg/L according to the drinking standard (WHO, 2004) and the FAO irrigation standard (FAO, 2005) were in the appropriate range. The pH value also was in the desired range, with an annual average of 7.8 in terms of irrigation and drinking. The results of examining the annual average of BOD5 also showed that this parameter was unfavorable based on the drinking standard, but it was in the desired range according to the FAO irrigation standard. The annual average of TDS showed that this parameter is in the unfavorable category in terms of irrigation, but in the favorable category in terms of drinking consumption. According to the results, the water quality of the river was in the Medium category in all different seasons and months during the year. The highest numerical value of NSFWQI was obtained in March with the value of 60.59 and the lowest numerical value of the mentioned index was measured at a value 54.21 in June. The total results which obtained from the study of Golin river water quality during one year (2019-2020) showed that the water of the river in terms of NSFWQI was in the medium category in all seasons. Disposal of household waste, animal waste, rural waste, agricultural wastewater and hot climate are the main reasons for the decrease in river water quality at the sampling station. Examination of physical and chemical parameters of Golin river and comparison of results with WHO drinking standard and FAO irrigation standard showed that DO, pH, NO3-, PO43- were in the desired category and BOD5, turbidity and TDS were classified as undesirable condition. However, it can be suggested that based on the results obtained from the index at the Najjar station, the water of the Golin River cannot be used directly for drinking and requires advanced treatment. For recreational purposes, the water must be used with caution. It was also found that the river water could be used for irrigation in agriculture and drinking of domestic animals.