Environmental management of the Bagmati River Basin

The Bagmati River is the principal river of the Bagmati Basin (ca. 3640 km²) in central Nepal. The river, fed by springs and monsoon rainfall, originates in the north of Kathmandu Valley (the capital of Nepal) and drains across the Mahabharat Range to the Gangetic plain. The Basin transacts three distinct latitudinal physiographic zones (Mountain, Siwalik and Terai) of the Nepal Himalayas. Hard rock geological formations at the Basin headwaters stand out as a resistant ridge complex compared to the weak and fragile rock formations at the middle stretches of the Basin.

The Bagmati Basin currently faces a number of serious environmental and ecological challenges. Urbanization and industrialization of the Basin headwaters at Kathmandu contributed to water quality deterioration with regional consequences on the aquatic ecosystem and on the health of the downstream sub-basin’s user groups. Increasing population pressure on the fragile mountain slopes has also resulted in the rapid degradation of the natural resources.

As a consequence, deforestation, soil erosion, landslides, siltation etc. are occurring in the upper and middle sections whereas sedimentation and flooding is frequent in the lower stretches of the watershed. This synergetic effect is of concern for the sustainable use of the resources and infrastructures.

The overall damage caused by the 1993 flood in the Basin has provided impetus to Nepalese planners, engineers, environmentalists, policy makers and stakeholders to think on the Basin-wide environmental perspectives for the overall sustainability of the project. This paper deals with the various facets of environmental management and monitoring of the watershed for its sustainable development.

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) sub-basin. 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.

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Arjun Paudel
Senior Divisional Engineer
Department of Water Supply and Sewerage
HMG, Nepal
GPO Box 7301 Kathmandu NEPAL

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