Energy from water
Bharat Jhunjhunwala (The Statesman, 17 June 2008)
The Planning Commission, in its Integrated Energy Policy Report of 2006, had declared hydropower to be the cleanest source of energy. It offered three reasons to back its
contention: it doesn’t lead to emission of green house gases as in energy produced from coal; it doesn’t cause deterioration in the quality of flowing waters; and there is no attendant problem of solid waste disposal as in thermal and nuclear energy. The recent
increase in the price of oil has made hydropower even more attractive for our planners.
However, this strong pitch for hydropower because it is supposedly clean is based on an inaccurate assessment. Studies by the
International Rivers Network indicate that tropical hydropower reservoirs emit more greenhouse gas per unit of power produced than thermal plants. Organic matter ferments in the base of reservoirs and produces methane which is let off into the atmosphere at the spillways. Hydropower reservoirs also prevent absorption of beneficial chemicals by free flowing waters. Most important, they arrest the sediments that are carried by our rivers to the coasts and prevent their erosion.
The sea waves have a natural tendency to hit the coasts, resulting in erosion. The impact gets neutralised by the inflow of sediment brought in by our rivers. The construction of reservoirs prevents this inflow of sediment and allows the sea to erode our lands.
The great plains of the Ganga and virtually the entire land mass of Bangladesh has been formed by the sediment brought in by the Ganga, the Meghna and the Brahmaputra rivers. The Department of Marine Geology and Geophysics, Cochin University of Science and Technology has conducted a survey of West Bengal’s Gangasagar Island. The data reveals that between 1976 and 1996, erosion by the Gangasagar took place at the rate of 0.8 square km per year. And during 1996-99, the rate of erosion increased to 5.5 square km per year, the reason being that the sediment was trapped by the dams. A study undertaken by Andhra University, Visakhapatnam, and Japan’s Yamaguchi University and Shimane University has estimated a net loss of 1836
ha of land during the past three decades along the Godavari delta shoreline. This has been attributed to the reduced sediment supply from an annual average of 145 million tons in 1971-79 to 87 million tons in 1980-89 and 56 million tons in 1990-98 due to construction of a number of dams.
The Geological Survey of Japan has observed: “It is estimated that about 30 per cent of the global sediments previously discharged to the oceans are now trapped in reservoirs behind dams. Because of the construction of the Aswan High Dam, the Nile river mouth area has experienced serious erosion, retreating more than 4 km during the last hundred years. Over the last 30 years, dam construction and increased water consumption have caused a dramatic decrease in the amount of sediment and water discharged from the Yellow River (Huanghe) in China. During the 1980s, sediment discharge from the Yellow River dropped to 70 per cent during the ’60 and the ’70 and to 30 per cent during the ’90. Moreover, since the Xiaolangzi Dam began operation in 1999,
discharge has become less than 10 per cent than during the 1960s-1970s, resulting in serious coastal erosion.”
The Government of India’s Coastal Protection and Development Advisory Committee (CPDAC) had prepared a Rs 1,600-crore national coastal protection project in 1998. The huge outlay makes it plain that we do not allow the rivers to flow in their natural course and thereby protect our coasts.
The last four minutes of the CPDAC meetings are available on the net. However, there is no mention of the impact of dams. Apparently, increased funds are sought to ‘prevent’ erosion of the coast while ignoring the erosion on account of dams. There is no effort to tackle the problem of erosion at the root ~ by stopping the
construction of dams.
Trapping of sediment in reservoirs makes the water ‘clean’, which means that it has a higher capacity to absorb sediment. Sediment-free water has an impact on the riverbed downstream.
Patrick McCully, in his study of dams titled Silenced Rivers, writes: “Clear water below a dam is said to be ‘hungry’: it will seek to recapture its sediment load by eroding the bed and banks of the river... Over time, all the easily erodable material on the riverbed below the dam will eventually be removed, and the bed will become ‘armoured’ with rocks... Riverbeds are typically eroded by several metres within a decade of the first closing of dams. Within
nine years of the closure of the Hoover Dam, hungry waters had washed away more than 110 million cubic metres of material from the first 145 kilometres of riverbed below the dam, lowering it in places by more than four metres. The deepening of the Colorado has undermined bridge foundations and rendered useless numerous intakes for the supply of municipal and irrigation waters.”
The environmental impact on such a scale has been overlooked by the Planning Commission when it declares that hydropower is the cleanest source of energy.
Bangladesh will be hit hard. Its coasts will be eroded just as those of
Gangasagar. This will be compounded by a rise in the sea level due to global warming. In a worst-case scenario the people of Bangladesh may enter India as refugees to escape the sinking land and rising waters. India does not have the right to arrest the sediment either way.
The United Nations has adopted the Convention on the Law of the Non-Navigational Uses of International Watercourses on 21 May, 1997. Clause 7.1 of the Convention states: “States shall, in utilising an international watercourse in their territories, take all appropriate measures to prevent the causing of significant harm to other watercourse States.” Clause 10.2 provides: “In the event of a conflict between uses of an international watercourse, it shall be resolved with special regard being given to the requirements of vital human needs.”
Experts say that international law gives precedence to the interests of downstream states over upstream states. We already have the experience of Farakka Barrage where we had to step back and accommodate the concerns of Bangladesh. A similar situation is likely to emerge with respect to the numerous hydropower dams being built by India on its international rivers. Eventually, India may have to dismantle these dams to allow sediment to flow to Bangladesh.
The Government of India should reconsider the clean chit provided by the Planning Commission to hydropower in the Integrated Energy Policy Report. Such contentious issues as the impact of hydropower dams on the declining quality of water, greenhouse gas emissions, erosion of the coastline, the bitterness with Bangladesh and the violation of UN Conventions should be sorted out before dams are built on international rivers.