Geo-Ecology of Trans-Border River System and Dams Between India and Nepal
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Water Woes In South East Asia: Geo-Ecology Of Trans-Border River System And Dams Between India And Nepal Amrita Chatterjee, Dr Dipayan Dey Institute of Management Studies Dehradun, India Abstract Himalayan rivers flowing through the Indo Nepal borders of Ganga Basin has made the floodplains of Bihar vulnerable to devastating flood rendering thousands of hectares of land as waterlogged fallows. Irrigation barrages control most of the tributaries modifying the flow of the main rivers and considerably influence aquatic biodiversity. Impacts on the fertile floodplains where empolderment for rice farming is practiced have already modified to an extent of more than 50% of the floodplains of Bihar state along the Indo Nepal borders. The international water regulation issues on high dams between India and Nepal is still in a stalemate whereas politicized Flood Games have become annual rituals of assuring flood hit people. The present paper reviews the problem from a conservationist angle in an attempt to suggest alternative policies and practices to save the ecology of these wetlands. Key Words: Rivers and Dams, Trans-border issues, South East Asia Introduction Drained mainly by the eastern Himalayan Rivers, the Ganges basin provides geo-ecologically diverse features, which are reflected in its resources. Being one of the most populous places on earth, there is, consequently, a substantial demand and competition for resources, particularly the water itself. Irrigation barrages control most of the tributaries modifying the flow of the river and considerably influence aquatic biodiversity. Impacts on the fertile floodplains where empolderment for rice farming is practiced have already modified to an extent of more than 50% of the floodplains of Bihar state along the Indo Nepal borders. The diverse and productive aqueous agro-environment of the basin is already under anthropogenic pressure and this is likely to increase in future. The present population of the Basin is around 500 million, which by 2030 would cross over to a billion, with almost half below the poverty line (Chapman 1995). This plain remains submerged under floodwaters for around 100-120 days a year between July and October. Major rivers of Nepal that contribute over 40 % of the total flow of the Ganges and over 70 % of its dry-season flow are Mahakali, Karnali, Gandak and Kosi of which the last two are looked up as the “sorrow of Bihar”. The total amount of water though enough to meet the social, economical and environmental requirements of this part of the basin, land man ratio and per capita food grain availability is steadily declining. The integrated development and utilisation approach of the basin’s huge natural resources have never been sought by the regional countries due to past differences in perception, legacy of mistrust, lack of political vision, and lack of goodwill (Ahmed et al. 2001). Basin Ecology Located in the north of Gandak-Kosi interfluves of Middle Gangetic Plains of North India at an altitude of 85-125 meters above sea level, the floodplains of North Bihar constitutes of a series of alluvial cones formed by master streams along with lower gradient slopes between them. The plain is absolutely featureless without even a single hill having an average gradient of 9.5 to 6.2 cm/Km towards southeast. Tributaries of the master streams meet at acute angles constituting dendritic drainage. In between the Gandak and Kosi system flows the Burhi Gandak, a tributary of Ganga that receives the floodwaters of Bagmati and distributes in the Gandak-Kosi systems (Sharma and Coutinho 1980). Gandak rises in the central Himalayas at an elevation of 7600 meters and flows for 425 Km draining 48,500 sq. Km. of which the catchments in India is 9540 sq. Km. the average annual flow is 522X108 cubic meters. Kosi originates in the Nepal Himalayas and also has seven constituent rivers originating from the snow peaks of Sikkim, Nepal and Tibet of which, Arun and Tamur are important. They join in Nepal and flow for 730 Km draining 86900 sq Km. of which 21,500 sq Km is in India. Its average annual flow is 617X108 cubic meters (Information Bulletin of Water Resources Dept. Bihar, 1993). Below the Chatra gorge, where Kosi enters the plain, there is a sudden break of slope having no sufficient space for the river to pass gradually through stages of grading and maturity (Enayat 1965). Thus the river has shifted its course westwards by 112 Km in 200 years, converting 7000-8000 sq. Km of arable land to waste wetlands. Vast amounts of sediment are transported downstream by the river and distributed across the fringing floodplains during the period of inundation. Ultimately, a large proportion of the sediment is transported beyond the coastal delta and into the Bay of Bengal. Estimates of the quantity of topsoil transported through the main channel are of the order of 240 million m³ yr ¯¹ (CPCB 1984), which is one of the highest sediment loads of any river. Within the catchments area there exist extreme variations in flow, both spatial and seasonal, to the extent that the mean maximum flow is 52.3 times greater than the mean minimum flow (Welcomme 1985). The flood season is more protracted in the lower sections of the river. The snow fed streams result from the melting of snow and glaciers from the heights of the Himalayas, which wash down heavy loads of sediments from the underlying moraines. Though there is some debate as to the relative roles of precipitation in the upstream catchments area or local rains in the annual flooding patterns (Chapman 1995), matter of considerable concern is in the upland regions, particularly in Nepal, that deforestation and degrading land practices are leading to increased erosion with higher sediment loads and charged flooding patterns within the river. The northern tributaries which enter on the left bank after descending from the Himalayas in Nepal, principally the Karnali (Ghaghara), the Buri Gandak, Gandak and Kosi rivers provide around 60% of the water within the basin. Floods and Water logging in Bihar The Existing Scenario Bihar (Figure 1a and 1b), after its bifurcation into Bihar and Jharkhand, has an area of 94163 squire kilometers and a population of 82.88 millions with a population density of 880 per sq Km. The 432 kilometer long Ganga bifurcates the state into two parts. There are 8 major rivers namely the Ghaghra, the Gandak, the Burhi Gandak, the Bagmati, the Adhwara group of rivers, the Kamla, the Kosi and the Mahananda. None of these rivers barring the Burhi Gandak originates in the state and they enter Bihar either from UP, West Bengal or Nepal. Burhi Gandak too, has most of its catchments in Nepal. There are 22 districts, located on the north of the Ganga and this alluvial plain, commonly known as north Bihar, is highly prone to flooding every year. About 76 per cent of the total area of north Bihar (5.4 million hectares) is reported to be flood prone and 81 per cent of the population there claims to earn its living through agriculture. This makes this area a tough place to earn one’s livelihood from an otherwise very fertile land. To prevent shift of the rivers and to save a vast population from annual flooding, most of these rivers were embanked in the five-year plan periods undermining the debate of over hundred years against embanking of the rivers. Some 3465 kilometer long embankments were built along these rivers during the plan period to protect 29.28 lakh hectares (LH) of land at a cost of Rs. 1827 Crores (till March 2003). At the same time, the flood prone area of the state has raised from 25 LH (1954) to 108.81 LH (2002-when last assessed) in the said period. The balance of about 80 lakh hectares of the flood affected area is yet to be tackled for which, apparently, no money is available as all the money that is allocated for flood control is consumed in maintaining the already constructed embankments. There has been, virtually, no addition in the embankment length of the rivers in Bihar for the past 17 years. The embankments along the rivers are in a dilapidated condition and 11 kilometers length of them was washed away in 2000-01 and another 25 kilometers in 2001.Thus, the state has been left with 3430 kilometers length of embankment now. It is amazing that despite the loss of 35 kilometers length of the embankments, the flood-protected area of the state remains the same at 29.28 LH. Some 9.41 LH land remains waterlogged in the state and a proposal to drain 4.41 LH of land at a cost of Rs. 941 Crores is awaiting sanction. According to the annual report of the Water Resources Department of Bihar (2002-2003), out of 9.41 LH waterlogged area in the state, some 1.5 lakh hectares of water logged land in the state has been cleared of water logging in the past. Of the remaining 7.91 LH waterlogged land, 2.5 LH is reported to be beyond redemption and the suggested use of that land is said to be that of aquaculture, fish farming and bio-drainage5. To save itself from the humiliation of answering inconvenient questions regarding water logging, the government has already declared Kusheshwar Asthan block, in Darbhanga district, as a bird sanctuary in 1994. The Planning Commission has directed the state to constitute a special task force to study the problem of water logging in the state and suggest measures to curb the menace. The task force identified 11 such schemes in the Gandak Command and 13 in the Kosi Command to be taken up at an estimated cost of Rs.