2024 年 22 巻 6 号 p. 255-270
The water quality of the geographically and culturally important Bagmati River is deteriorating due to the mixing of highly polluted tributaries and untreated domestic and industrial waste. Real-time physicochemical data was collected from the tributaries and mostly polluted sites along the Bagmati River in the Kathmandu Valley. The results showed that as compared to the tributaries, the Bagmati River was less polluted before the confluence. The oxidation-reduction potential and dissolved oxygen were recorded high up to the middle of the observation domain and reduced to extremely low adapting to hypoxic region downstream sites. The water quality index (WQI) of Bagmati River was determined using the assigned weighted value (model A) and the weight arithmetic index of water quality parameters (model B). It was as high as 400 (model A) and 130 (model B) downstream in the Bagmati River. The WQI value showed that all the rivers inside the Kathmandu Valley were highly polluted and unfit for human use. Human activities such as the direct discharge of domestic effluent, disposal of solid waste at the bank of the river, and the mixing of highly polluted tributary excessively loaded contaminants, turned the Bagmati River into a biologically dead river downstream.
