Tuesday, September 28, 2010

River Ganga & Ecology

Sen, H.S. (2010). Drying up the Ganga: An issue of common concern to both India and Bangladesh. Current Science 99(6)25 September:725-727


COMMENTARY
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Drying up the Ganga: An issue of common concern to both India and Bangladesh

H. S. Sen

A number of hydel projects and other schemes diverting water in the Ganga-Bhagirathi river system upstream to Farakka barrage act as an impediment to uninterrupted flow of water into the barrage. This is a major reason, besides others including design aspect of the barrage itself, due to which there is fast deterioration of the hydrology of both Hugli-Bhagirathi and Ganga-Padma river systems. In order to ensure livelihood security in this ecosystem spanning over both India and Bangladesh there is need for close introspection and appropriate action in a holistic mode to restore hydrology of the river system.

The ecological sustainability of both South Bengal (below Farakka barrage) in India and almost entire Bangladesh (command area under Ganga-Padma river system) is under increasing threat due mainly to unplanned diversion of water in the upstream of the Ganga-Bhagirathi region under Indian territory. The article proposes that introspection be made and appropriate action taken in order to ensure uninterrupted flow of water into the barrage to save the ecosystem spanning over both India and Bangladesh.

Neo-tectonic movement

The tidally dominated area (TDA) is located at the tail end of Ganga basin. Due to neo-tectonic movement during 16th to 18th century the Bengal basin had tilted easterly along a hinge zone starting from Sagar (Indian Sundarbans) to north of Malda (West Bengal, India), finally curving towards Dhaka (Bangladesh). As a result of this, the flow of Ganga river started coursing through the river Padma in Bangladesh leaving Hugli with the erstwhile course as a mere tidal channel. During 16th – 18th century innumerable distributaries were generated from Ganga which formed huge network of creeks and channels within Sundarbans delta and other parts of TDA in both India and Bangladesh and many of them now act as brackish water channels.

Need for a barrage on the Ganges

The construction of a barrage across Ganga and diversion of water towards the Bhagirathi was first suggested by Sir Arthur Cotton in 1853, following which many other British engineers supported the idea although they were not unanimous on the location of the construction. The construction now located at Farakka in West Bengal, known popularly after the place, 12 km upstream of the diversion of the river into Hugli-Bhagirathi flowing through India and Ganga-Padma into Bangladesh and their tributaries ─ all finally terminating into the Bay of Bengal ─ then started in 1962 and completed in 1971.

The impact

The hypothesis of arithmetic hydrology worked out in favour of the barrage was subsequently proved too inadequate to bring about any positive impact either to flush out sediment load to increase navigational prospect for the Kolkata Port or to share dry season flow between the two countries for their mutual benefits, the very purposes for which it was conceived. It should not be lost sight of that the prospects of agriculture and allied activities and livelihood security should depend upon geo-hydrology and, in turn, on the sedimentation and hydrology in the TDA. It is thus true that the dynamic equilibrium of Ganga river and its tributaries have been largely disturbed due to inadequate planning for the construction of the barrage. It is not intended, neither there is scope, to discuss all factors in details in this article, but will touch upon only the issues related to upstream flow of water affecting hydrology in the downstream with suggestions for future attempts for improvements.

There are various sources contributing sediment load into the Bhagirathi-Hugli river. It has been worked out in 2006 that the annual sediment load transported below Diamond Harbour was 23.68 x 106 tonnes, and about 13.20 x 106 tonnes between Nabadweep and Diamond Harbour, while about 26.93 tonnes get deposited or remain in circulation between Diamond harbour and Sagar each year1. The sediment movement is tide dominated and a part of the total, about 4.9 to 14.67x 106 tonnes, is likely to be pushed back during ebb flow, exact quantum of which is difficult to estimate. The Ganga-Brahmaputra river system causes largest amount of silt deposition in the order of 1667 million tones per year1, although the exact amount is largely debatable. The huge amount of sedimentation load and the resultant reduction of river cross-sections have its immediate impact on colossal loss of soil due to erosion of river banks and floods finally resulting in consequent loss of human population and properties as an annual ritual observed each year on both sides of Bhagirathi. Ever escalating amount of dredging1 is causing significant impediment to navigation in Kolkata Port and mounting increase in expenditure (Figure 1). This along with significant reduction of water supply is responsible for deteoriorating soil and water quality affecting agriculture and livelihood particularly in the tidally dominated parts of Bangladesh and, to some extent, the Indian Sundarbans2. Deteriorating hydrology of the rivers in both India and Bangladesh caused increasing occurrence of flood in both countries with time3 (Figure 2).


On Bangladesh part, the diversion of Ganga water appears to have reduced the dry season discharge of Ganga and Gorai, the latter being one of the distributaries of Ganga that supplies water from Ganga to south west region of the country. This reduction of discharge of Gorai river in Bangladesh is reported to have increased the sedimentation and salinity of the southwestern part of the country. A perusal of the data due to installation of Farakka barrage shows that the river water salinity in the Sundarbans region of Bangladesh is much higher in the southern and southwestern rivers, moderate in middle areas, and lower in the northern part of Sundarbans4 (Figure 3). No such detailed study on soil or water quality parameters was however undertaken in India. It is opined that that a holistic approach is required to ensure security to the inhabitants on either side of Ganga1.

Suggestions for future

Appropriate interventions are desired to resuscitate Ganga with the aim to arrest the adverse trend at the earliest and, in due course, reverse it for improved livelihood through (a) higher productivity in agriculture, aquaculture, forestry, etc. under favourable soil and water conditions, and (b) reduced hazard due to flooding of low lands and erosion of river banks.

There is need for a study in holistic mode in order to regulate water flow through construction of structures and diversion of water at strategic points along the river systems upstream in order to ensure minimal required water flow to and through the Farakka barrage. The task of India in this regard sharing entirely the upstream flow of water passing through a number of states before reaching Farakka barrage is therefore imminent which I believe has been grossly overlooked in as far as its application was concerned till date. The National Ganga River Basin Authority under Government of India under its jurisdiction should conduct a detailed study and formulate plan immediately for strict compliance for upstream regulation of water flow before it is too late. If necessary empowerment through legal action may be thought of. The shortcomings in planning and execution of the much hyped Ganga Action plan (GAP) should be carefully studied. There are disturbing news of state governments drawing up massive plans for a number of hydel power projects and a number of non-government organizations even diverting water at their wills in this stretch of the river course in order to meet their sectoral needs, thereby leading to drying up the river flow5, overlooking the interest of the nation at large, and in long term perspectives, the ecological sustainability of both India and Bangladesh. Any action on the future plans for improvement will be futile if the upstream regulation is not viewed seriously enough, not only to stop unplanned use of river water forthwith, but also take positive measures to augment it as far as possible to its original state, no matter how efficient the design of the barrage and the downstream regulation of the water flow are. Finally, there is need for reworking on the water allocation between the two countries round the year based on minimum and assured flow input into the barrage with cooperation of all states and the Government of India and realistic inputs received from all concerned with scope for periodical monitoring alongside vigilance of high order in order to achieve success on a long term basis.
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1. Rudra Kalyan. Shifting of the Ganga and land erosion in West Bengal – a socio-ecological
viewpoint. Centre for Development and Environment Policy, Indian Institute of
Management, Calcutta, 2006, CEDP 08, 59p.
2. Sen, H.S., Burman, D. and Mandal Subhasis. Improving the rural livelihoods in the Ganges delta through integrated, diversified cropping and aquaculture, and through better use of flood or salt affected areas, Technical paper presented in International Workshop on CPWF Basin Focal Project for the IG Basin, "Tackling Water and Food Crisis in South Asia: Insights from the Indus-Gangetic Basin", held at India Habitat Centre, New Delhi, 2-3 Dec, 2009, International Water Management Institute.
3. Mirza, M. Monirul Qader, Warrick, R.A., Ericksen, N.J. and Kenny, G.J. Are floods getting worse
in the Ganges, Brahmaputra and Meghna basins? Environmental Hazards, 2001, 3, 37-48.
4. Islam Shafi Noor and Albrecht Gnauck. Mangrove wetland ecosystems in Ganges-Brahmaputra delta in Bangladesh. Frontier Earth Science China, 2008, 2(4), 439-448.
http://resources.metapress.com/pdf-review.axd?code=j6821567240w8g3u&size=largest

5. Times of India. Hydel plants will dry up Ganga: CAG, 2 April, 2010.
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H.S.Sen is former Director of Central Research Institute for Jute & Allied Fibres (ICAR) at Barrackpore, WB, 700 120, India. Present address is 2/74 Naktala, Kolkata 700 047, India.
email: hssen.india@gmail.com, hssen2000@hotmail.com