Bagmati and Narayani are the major transboundary river systems of Nepal. These rivers are of importance due to its high aesthetic, religious, social as well as economic value. Water quality of the rivers has been crosscutting issues as it influences the ecology as well as the people in number of ways. Water quality affects aesthetic value, use value, economic value and life sustaining capacity of the river. Thus degradation in water quality of these rivers may give rise to conflict and hamper the political relationship with India. In the last decade there has been substantial change in water quality of these rivers due to blooming urbanization and industrialization. To see the extent and magnitude of the river water quality, monthly monitoring of the rivers were conducted at seven sites of the Bagmati River, five sites of Narayani River and one site of Rapti River, the tributary of Narayani. From the results of the monitoring it can be derived that there has been alteration in water quality both spatially and temporally with the changing trend of development and human livelihood. The impacts have been severe in certain segments of river especially in urban centres. In those sections the nutrients and oxygen demand load is excessively high and dissolved oxygen is alarmingly low. The main cause of pollution in Bagmati River is point sources of municipal effluents and industrial effluents, solid wastes dumped in the river and riverbank, destruction of vegetation along riverbanks and alteration in river bed by sand mining. The causes of pollution in Narayani River are non-point sources such as runoff and large point sources like industries. In the above rivers water quality was found to improve during monsoon season in polluted sites and degradation of water quality in the same time was observed in unpolluted sites. But by virtue of self-purification capacity of the rivers, they regain its prime condition before they reach India. Thus water that enters India is perfectly good for domestic use, industrial use, and commercial use as well as for healthy aquatic ecosystem. Nepal being upper riparian has not affected the use, social, aesthetic and economic value of downstream water uses by India, the lower riparian. Nevertheless some positive steps should be undertaken to have holistically clean and pure water flowing at each and every spot of the river, as the measures for conservation and sustainable use of river.

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