Human activities during recent decades have led to increased degradation of the river water environment in South Asia. This degradation has led to concerns for the populations of the major cities of Nepal, including those of the Kathmandu Valley. The deterioration of the rivers in the valley is directly linked to the prevalence of poor sanitary conditions, as well as the presence of industries that discharge their effluents into the river. This study aims to investigate the water quality aspect for the aquatic ecosystems and recreation of the major rivers in the Kathmandu Valley using the Canadian Council of Ministers of the Environment water quality index (CCME WQI). Ten physicochemical parameters were used to determine the CCME WQI at 20 different sampling locations. Analysis of the data indicated that the water quality in rural areas ranges from excellent to good, whereas in denser settlements and core urban areas, the water quality is poor. The study results are expected to provide policy-makers with valuable information related to the use of river water by local people in the study area.