By Dawa Tshering
The prime minister Manmohan Singh during his recent visit to China did not get any positive answer as to what Beijing is upto to tame the mighty river originating from Tibet. It is certain the dam-building activity upstream by China will do immense damage to the thousands of years old civilisation and still undiscovered biodiversity wealth downstream — in Arunachal Pradesh and Assam.
The Brahmaputra begins its journey as the Tsangpo, the highest river in the world, from a spring called Tamchok Khambab, at an elevation of 5,150 metres in Kanglungkang glacier, south-east of Mansarovar lake in Southern Tibet. The Tsangpo flows 1,625 km in Tibet, 918 km in India (278 km in Arunachal Pradesh as the Siang river and 640 km in Assam as the Brahmaputra) and 363 km in Bangladesh as the Jumna before it joins a tributary of the Ganga and disappears into the Bay of Bengal. The Brahmaputra receives as many as 22 major tributaries in Tibet, 33 in India and three in Bangladesh. Many of the north bank tributaries are of Himalayan origin, fed by glaciers in their upper reaches, the Subansiri, the Jia Bharali (Kameng), and the Manas. The Dibang and Lohit are two large tributaries emerging from the extreme eastern flank of the Himalayas, while the Jiadhal, the Ranganadi, the Puthimari and the Pagladiya are some of the major tributaries with sources in the sub-Himalayas.
This unique geo-environmental setting in the eastern Himalayas is a fragile geological base characterised by an active seismo-tectonic instability zone and a potent monsoon regime. More recently, it has been in the news because of the drastic rise in rate of glacial melt. All of these are cited as the primary reasons for the excessive flooding, landslides, erosion, siltation and braiding of the Brahmaputra. Experts also point out the inadequate capacity of the river channel due to its inherent braided nature which causes spilling of floodwater over the banks as well as drainage congestion at the outfall of tributaries during the high stage of the main river. Intense land use pressure and high population growth especially in the floodplain belt and ad hoc or temporary flood control measures are other factors that cause and intensify destruction by floods in the Brahmaputra basin.
For Assam, the floods of June 2012 have been recorded as the worst in the last 10- years. According to Oxfam India, nearly 2.4 million people were affected and half a million displaced. Scientists may be reluctant to cite climate change as the direct cause of the 2012 flood, but they are unanimous that the frequency of such incidents will increase drastically in the future.
The increase in the frequency of floods and intensity of erosion is not only threatening the lives of the people in the state of Assam but has led to permanent loss of land, livelihood and, as in the case of my last destination, the fast disappearing river island of the very culture and identity of its people.
Ironically, the construction of multipurpose dams was originally proposed as a practical method for controlling floods and generating electricity in the Brahmaputra valley. According to the Central Electricity Authority (CEA) study of the Brahmaputra basin in 2001, 168 hydropower projects with an estimated capacity of 63,328 MW have been identified for construction in the Northeast region, which earned it the title “future powerhouse of India” at the Northeast Business Summit in Mumbai in July 2002. Soon after, in 2003, the ministry of power launched the 50,000 MW Hydro Initiative largely focusing on the Brahmaputra basin. Till October 2010, the government of Arunachal Pradesh has already allotted 132 projects to companies in the private and public sector for a total installed capacity of 40,140.5 MW, with around 120 of these projects involving private players.
Now activists allege that flood control was merely a pretext for stealing natural resources and spawning a multi-million dollar hydro development scam in the northeast. The idea that multipurpose dams can help flood control along with hydropower generation has already proven unviable and dangerous. India’s Hirakud dam was built in the name of flood control, yet extreme floods in the Mahanadi delta between 1960 and 1980 were three times more frequent than before Hirakud was built. Panic release of water from Hirakud has been blamed for much of the devastation. In 1978, nearly 65,000 people were made homeless by floods exacerbated by forced discharges from Bhakra dam. There are several instances of floods worsening because waters were held back while the reservoir filled, and then suddenly released to prevent the dam being over topped. The risk increases twice over now that private companies have bagged the contracts: they will prioritise profits from electricity generation over flood control.
Meanwhile, confirming long held fears of the local people, the Chinese State Council, or cabinet, has now publicly approved plans for the construction of three new hydropower projects in the middle reaches of the Brahmaputra, or Yarlung Zangbo as it is known in China. The projects were listed in an energy development plan for 2011-15 announced in January 2013. Work has already begun on a 510 MW dam in Zangmu in the Tibet Autonomous Region.
China has assured India that the new hydropower dams it is planning to build on the Brahmaputra will not affect flood control and environmental efforts across the border in the Indian northeast. But there is a real and palpable fear amongst the local population about the Chinese damming of the Brahmaputra and what this could mean for the river and its people.
It is a fact that dam designers work on the assumption that historic hydrological variables such as average annual river flow, annual variability of flow, and seasonal distribution of flow are a reliable guide for the future but as is now abundantly clear, the past climate is no longer a sufficient guide to the future. As climate change takes hold, there’s already a significant change in annual rainfall patterns and worse, the rate of snow pack melting has speeded up dangerously and instances of unseasonal flooding have increased drastically. The ruins of hundreds of embankments built as first line of defence in the 1980s and 1990s are a testament to that reality.
The writing is already on the wall. We are seeing the effects of climate change and to build worthwhile flood defences it is important to be able to accurately predict the climate of the next 50 to 100- years.INAV