The Bagmati River originates just below the summit of Shivapuri Hill and is fed by springs and monsoon rainfall and a number of tributaries as it flows down from the Kathmandu valley floor and passes through the valley at Chovar. The river is fed by a number of tributaries originating at Mahabharat and in the Chure Range before it reaches the Terai at Karmaiya. The Bagmati River Basin, based on morphology, land-use etc., can be divided into different sub-basins viz. Upper Bagmati, Upper Middle Bagmati, Lower Middle (Terai) Bagmati and the Lower Bagmati (Terai) subbasin. The total area of the Basin within Nepalese territory is about 3638km2. In the 1991 census, the total Basin population was given as 1.6 million of which 61.5 per cent inhabit the Upper Bagmati sub-basin, where the capital city of the Kingdom of Nepal, along with other four municipalities including a number of village development committees, are situated. It is also reported that a total of 2174 out of 4271 water polluting industries operating in the country are now in operation in the Upper Bagmati sub-basin. Increasing degradation of the Bagmati Basin has been evident in recent years due to rapid population growth and expansion of the urban areas within the upper Bagmati sub-basin. Uncontrolled disposal of untreated wastewater (domestic, industrial, solid waste leachate, agricultural runoff etc.) in the rivers has far surpassed the assimilative capacity of the river. Likewise, deforestation, soil erosion and landslides have been causal factors of Basin degradation which is being increasingly threatened by damage to the infrastructure of reservoir, barrage, canals, bridges and roads from debris, tree and logs carried by the river during the monsoon season.
A comprehensive environmental study of the Bagmati River Basin was carried out by the Water and Energy Commission Secretariat using a team of experts to formulate concrete proposals for mitigation measures for:
• pollution abatement and improvement of the river water of the river thereby enhancing its assimilative capacity;
• decreasing suspended solids and siltation in river beds, canals and irrigated fields; and to
• minimizing threats to the stability of infrastructures.
The concept of Basin-wide planning for sustainable development is still new to Nepal. A development programme based on, and implemented by, administrative units could not handle and foresee the environmental impacts in the surrounding vicinity. A basin is a land unit defined by the natural barriers and the natural resources within such boundaries have intricate relationships. Exploitation of one resource has a direct impact on the other. The study was intended to evaluate the environmental conditions of the existing Bagmati River Basin in order to help in the appropriate selection of development projects for the Basin development in a sustainable manner.The study approach was initiated through the collection of secondary information. The collected information was reviewed, analyzed, interpreted and evaluated in a meaningful way to meet the study objectives. Most of the secondary information available in the limits of political boundaries was transformed into the Basin context. As the study emphasizes river pollution and the effects of erosion and sedimentation at the Karmaiya barrage site, the field study was mainly focused on these issues. However, other environmental issues were also dealt with, to some extent, with the objective of assessing their effects in terms of the sub-basins. In order to collect baseline data and information about the state of the existing environment in the Basin, separate matrices on baseline conditions and problems concerning natural resources and environment were developed and used for this purpose. The matrix on baseline conditions and problems definition regarding natural resources was designed to incorporate information about the importance, extent of current use, availability of resources for future economic development, likely future demand, conflicts and availability of alternative resources. Likewise, the matrix to collect data on baseline conditions regarding the environment included the significance, extent and trends of environment degradation, effectiveness of current control measures, extent of environmental degradation with new protection measures and the need for new environmental protection measures. A checklist on the status of data availability on the Basin was also developed and used to facilitate the study objectives.