Earthquakes, Dams and Water in South Asia

21 April 2016 Mervyn Piesse, Research Manager, Global Food and Water Crises Research Programme Download PDF

Key Points

  • South Asia has immense hydropower potential, which many countries are beginning to develop. More than 400 dams are either planned or under construction in China, India, Nepal, Pakistan and Bhutan.
  • As the region is geologically young the potential for earthquakes is heightened. Earthquakes pose considerable risk to dam infrastructure and downstream communities.
  • Dams could interact with the region’s geology to hasten the onset of earthquakes, but there is no conclusive evidence to suggest that this is the case.
  • Changing climatic conditions could increase the evaporation rate and reduce the amount of water flowing into dams, leaving many of them incapable of reaching their full generating potential.

Summary

South Asia has considerable hydropower potential. Harnessing this potential would bring both advantages and risks to the region. Developing hydropower plants would produce significant amounts of electricity that could fuel development, however, large dams pose flood and earthquake risks that could devastate the region. Regional rivers upon which the dams are to be constructed also cross numerous state boundaries, potentially increasing tensions between countries. Changing climatic conditions, melting glaciers and increasingly unpredictable weather patterns could make the stable operation of hydropower plants difficult, calling into question their long-term utility for the region.

Analysis

Dams have been used for centuries and generally have been used for at least one of the following four reasons: crop irrigation, electricity generation, water supply or flood control. The International Commission on Large Dams, an international non-governmental organisation that aims to provide a forum for the exchange of knowledge and experience in dam engineering, records over 33,000 dams worldwide with most of them developed for irrigation. Approximately 5,300 large dams currently operate in Pakistan, India, Nepal and Bhutan.

A large water storage dam consists of a concrete wall at least 15 metres in height,  a grout curtain to minimise leakage of water through the foundations, a spillway for the safe release of floodwater, a bottom outlet for lowering the reservoir in emergencies and a water intake that allows water to be used for industry.

This paper will focus exclusively on hydropower dams as most of the large dams planned for construction in South Asia are designed for this purpose.

Hydropower in South Asia

South Asia is undergoing a boom in dam development and construction with hundreds of dam projects planned. Countries in the region want to tap into the vast hydropower potential that the rivers flowing through their territories could provide. Pakistan, India, Nepal and Bhutan have begun to utilise their rivers for power generation, however, as the following table shows, they have developed relatively little of their feasible capacity.

Hydropower in South Asia

Installed Capacity (GW) Feasible Capacity (GW)
Pakistan 6.6 59
India 39.5 84
Nepal 0.7 43
Bhutan 1.5 24

Source: economist.com

The larger regional economies, China and India, are working on their own hydropower projects and are also investing in those of Nepal and Bhutan, both of which receive considerable amounts of revenue from electricity exports. If all the projects go ahead, the Himalayan region, which feeds the rivers of South Asia, could have the highest concentration of dams in the world.

There are plans for over 400 dams to be constructed across China, India, Pakistan and Bhutan. The Himalayas are the world’s youngest mountains. They were formed 50 million years ago when India – then an island – collided with the Eurasian landmass. The Indian subcontinent continues to push several inches north each year, putting strain on the region’s multiple fault lines. As the region is one of the most seismically active in the world, there is a risk of dam infrastructure becoming damaged as a result of earthquakes. If a dam were to collapse as the result of a severe quake, tons of water and rubble would rush downstream potentially destroying anything in its path.

By examining the hydropower plans of each of the four regional states it becomes clear that the advantages of hydroelectricity are accompanied by considerable risks. The rivers that flow through the region cross numerous interstate boundaries and extensive damming in one country could contribute to resentment and animosity in a downstream neighbour. It is highly unlikely that the construction of dams on its own will lead to conflict between regional states, but it could add to the underlying conditions that lead to the outbreak of conflict.

Pakistan

Most of Pakistan’s water is sourced from the Indus River. It is no surprise that most of its hydropower plants are also located on this river. The three largest hydropower plants, Tarbela, Ghazi-Barotha and Mangla, rely on the Indus River directly or, in the case of Mangla, one of its tributaries. The majority of Pakistan’s dams are designed to provide water for irrigation with power generation being a secondary concern.

As the country has long grappled with an electricity deficit dams are increasingly being viewed as a potential solution. China has invested in largescale hydropower projects throughout Pakistan. The Karot plant, which once built will provide 720MW from the Jhelum River, is the most recent Chinese-backed project to commence. Pakistan already depends on hydropower for about 30 per cent of its electricity. Demand for electricity is set to increase by eight per cent per year, but lower water levels threaten to disrupt its ability to maintain a stable supply.

Micro hydropower plants are becoming increasingly popular in remote areas of Pakistan that have not been able to get access to established electricity networks. These power plants are capable of providing small, remote settlements with enough energy to meet their daily requirements. It is difficult for service networks, such as electricity and water, to reach these isolated settlements and inhabitants have relied upon alternative sources of fuel for cooking had heating. As these communities no longer need to cut trees to produce wood for fuel natural forests are reportedly beginning to recover.

Declining water levels in dams have contributed to animosity with neighbouring India, which has been accused of using too much water upriver and depriving Pakistan of this vital resource. A greater reliance on hydropower, in both India and Pakistan, could heighten tension between the two neighbours over the sharing of Indus water.

Pakistan demonstrates the benefits and drawbacks of largescale hydropower projects. Its reliance on hydroelectricity has provided it with a relatively clean energy supply but has also fuelled disputes with India that have the potential to further sour the tenuous bilateral relationship.

India

India is similarly dependent on a few major rivers for its irrigation and hydropower needs. Water stress is increasing in India due to widespread shortages largely brought about by poor water management. Prime Minister Narendra Modi plans to construct about 200 hydropower projects in the north-east of the country while a further 30 dams are set to be built as part of the National River Inter-Linking Project that aims to divert water to agricultural regions.

Former Prime Minister, Atal Bihari Vajpayee, displayed similar interest in hydropower projects in 2003 when he floated the idea of developing 162 hydropower stations to generate 50,000MW by 2025. These projects were largely abandoned due to floods, landslides, rising construction costs and popular opposition in the states in which they were to be built. While Modi has displayed a desire to build dams, his plans are by no means assured as the problems the dam programme faced a decade ago have not gone away.

The cost of construction is probably the largest hurdle that will need to be overcome if all planned dams are to be realised. A number of private companies are reportedly beginning to abandon their plans to develop dams on the Brahmaputra in the country’s north-east. Many of the projects are no longer seen as cost-effective, particularly as the developers have faced numerous challenges from local communities, bureaucracy and a lack of supporting infrastructure such as roads and powerlines.

Increased Chinese interest in damming the Brahmaputra, known as the Yarlung Tsangpo in China, could contribute to greater animosity between the two neighbours. The recently constructed Zangmu Dam in Tibet has caused controversy in India. If China continues to construct dams in Tibet the relationship could fray further, particularly if India becomes more dependent on its own dams for power generation.

Nepal

Over 90 per cent of Nepalese electricity is generated by hydropower plants. These are predominantly run-of-river. They do not trap or store water, but their electricity output diminishes during the dry season. Storage dams largely overcome this limitation, as large amounts of water can be released year-round to sustain a constant rate of energy production. In Nepal, a single storage dam, the Indra Sarovar, supplies water to the Kulekhani hydropower plant.

In August 2014, shortly after he was elected, Modi became the first Indian prime minister to visit Nepal since 1997. He negotiated an agreement to finance the construction of two electricity transmission lines and the construction of the Pancheshwar hydropower station. Modi’s visit, so early in his term of office, suggests that he wants to develop the electricity-sharing agreement and increase the amount of electricity that his country purchases from Nepal.

In the aftermath of the 7.8 magnitude Gorkha earthquake that struck Nepal on 25 April 2015, at least 14 of its hydropower dams were damaged. The national grid lost 150 MW of electricity and a crack formed in the retaining wall of the Indra Sarovar. At least 18 aftershocks were recorded in the days following the quake. Just over two weeks later another 7.3 magnitude earthquake struck east of Kathmandu. While none of the country’s dams failed, the damage highlights the vulnerabilities that come with a high reliance on hydropower.

Bhutan

The small Himalayan kingdom of Bhutan acted on an opportunity 30 years ago to diversify its predominantly agrarian economy. It began to harness the energy generating potential of its fast-flowing rivers by constructing hydropower dams. With financial backing from India, it has built five plants that are capable of producing up to 1,500 MW, a mere 16 per cent of the amount that could feasibly be developed.

According to the Asian Development Bank, about 70 per cent of electricity generated in Bhutan is exported to India and this provides the government with more than 40 per cent of its revenue. Roughly 20 per cent of GDP is derived from the sale of hydroelectricity. The country is highly dependent on the production and sale of hydropower.

Thimphu has plans to increase the country’s hydropower production to more than 10,000 MW by 2020. Most of this increased production will be exported to India. As of early 2014, less than 20 per cent of this target has been reached. By 2018, two large projects are expected to come online and bring the hydropower generating capacity of the country to 3,240 MW. It is unlikely to achieve its 10,000 MW target by 2020, however, as there are no other significant projects that will bring capacity up to this level by the end of this decade.

Hydropower availability is seasonal, during the winter months – when river flow is naturally lower – Bhutan often struggles to meet domestic power demand. In some months electricity generation declines from 1,500 MW to 284 MW. Alternative sources of energy, such as wind and solar, are beginning to be developed to overcome this limitation to at least meet domestic electricity demand.

Bhutan’s economy is dependent on the generation of hydroelectricity and is highly vulnerable to any disruption in the generation of hydropower, whether this comes from floods, earthquakes or lower water flows. It also demonstrates the risk of concentrating on one form of electricity generation. Without a diverse array of electricity supply options the economy will struggle to develop.

Earthquakes and Dams in the Himalayas

The Himalayan region, in which South Asian countries are concentrating their dam building activities, is one of the most seismically active regions of the world. As more dams are built the risk of catastrophic failure as a result of earthquakes increases. Most dams are built to withstand earthquakes, however, in the event of a particularly destructive quake, even the most robust dams could be at risk of failing.

In the event of an earthquake dams can both cause and alleviate danger. If a quake severely damages dam infrastructure, a large cascade of water could flood areas downstream. Natural dams made of rock, sediment and ice, called moraines, can also break or shift as a result of quakes, erosion or an increase in water pressure resulting in glacial lake outburst floods (GLOF). Large GLOFs can disperse millions of cubic metres of accumulated water along with large boulders, silt and sediment in its path. If not properly prepared for, GLOFs can overwhelm dams and weaken their structural integrity, putting downstream communities and infrastructure at increased flood risk.

On the other hand, dam networks can be used for flood control as they can prevent large floods of water from rapidly flowing downriver. If properly managed dams can release stored water to contain the increased upstream flow before it rushes further downstream.

Dams can either alleviate or contribute to the worst impacts of earthquakes. Nepal, Bhutan, the Karakorum mountain ranges of northern Pakistan and India, and parts of Tibet are at risk of GLOF events that could be managed by a network of dams. Building dams just to manage these isolated events, however, is probably not the best use of state resources and there are other ways to relieve the pressure on naturally occurring dams to avoid GLOF events.

The Theory of Reservoir-Induced Seismicity

Geologists do not just fear the destructive potential of dams after an earthquake. Those that subscribe to the theory of reservoir-induced seismicity (RIS) claim that large dams can contribute to destructive quakes. The theory suggests that the weight of water behind a dam, in addition to water seeping into fissures in rocks below it, can produce shearing stress strong enough to worsen, or trigger, an earthquake. According to RIS theory, dams do not cause earthquakes but can cause a build-up of tectonic strain energy that could eventually be relieved through an earthquake. Distinguishing between naturally occurring earthquakes and those encouraged by human engineering is difficult, particularly as operators of dams are reluctant to acknowledge that they could be contributing factors. The phenomenon is perhaps confused further by opponents of dams that amplify the risk of RIS in an attempt to prevent the construction of dams.

The theory has been around for many decades, but remains poorly understood. In the 1940s, ten years after the opening of the Hoover Dam in the US, scientists noticed that seismic activity in the area surrounding the dam had increased. A 1967 earthquake in India has been attributed to the construction of Koyna Dam. Seismic activity around China’s Three Gorges Dam has also increased since it began to be filled, but scientists continue to debate the accuracy of RIS. It has been alleged that since 1929 at least 100 large dams have experienced RIS, however, the majority of these have resulted in relatively small tremors, with only four major events above magnitude six.

Speculation surrounding RIS was rekindled following the destructive Sichuan quake of 2008. Scientists from China and the US suggested that the Zipingpu Dam, located 5.5 kilometres from the quake’s epicentre, could have contributed to the 7.9 magnitude temblor. Conclusive evidence that links large dams to earthquakes is hard to come by, suggesting that this is an area that would benefit from further investigation and research.

Climate Predictability, Water Availability and Dams

Dams are unlikely to function well in the event of increasingly unpredictable and variable weather. Shifting rainfall patterns and other environmental uncertainties could decrease river flows and reduce the amount of water available to dams. In drought conditions the amount of electricity produced by hydropower plants declines, in severe cases the generating capacity of dams becomes negligible as they are turned off to prevent damage to turbines.

Ensuring that the new dams have an adequate amount of water to generate hydroelectricity is a looming challenge for South Asia. Currently, the region views its hydropower capacity as an untapped resource that, once developed, would provide it with almost limitless cheap electricity. The region’s hydropower would become an environmentally friendly source of economic strength. A less stable climate, however, could make the region’s growing reliance on hydropower a potential weakness.

Increasing rates glacial melt is a major concern for South Asia’s hydropower generators. Glaciers act as natural reservoirs as they store water in the winter and release it slowly over the summer as the ice melts. If glaciers continue to recede they will no longer be capable of storing the same volume of water as before. Even if the region receives the same amount of rainfall more of this water will remain liquid which evaporates at a faster rate than ice. Over time, the amount of water reaching Himalayan dams is likely to decrease and reduce their operational capacity.

As weather patterns shift and rainfall becomes more erratic it is likely that the dams will not be fully operational for large parts of the year. Increasing demands for water from agriculture, industry and households could also threaten the long-term utility of the power generating technology. Hydropower will only be able to meet the region’s electricity needs as long as weather patterns remain relatively predictable and it is looking increasingly likely that this will not be the case.

Many dams in the region are already incapable of providing electricity throughout the year. The Indra Sarovar storage dam, in Nepal, for instance, is dependent on steady rainfall during the wet season. In a year of normal rainfall the water that it captures in the wet season is released during the dry season to ensure that electricity can still be produced. In 2008, when Nepal received less than average rainfall, its water level was very low. A load-shedding initiative was implemented in 2009 to conserve the reservoir’s water level to ensure that electricity could continue to be provided. As a result, electricity was cut for up to 16 hours each day to ensure that the limited water supply would last for the entire dry season.

Given the great financial cost of developing and maintaining hydropower plants, leaders need to consider the long-term efficiency of such facilities in meeting their country’s energy requirements.

Conclusion

Dams bring both benefits and risks to South Asia. Through the development of micro hydropower plants, isolated parts of the region now have access to electricity and have greater developmental opportunities. Largescale hydropower plants have also generated relatively clean and stable electricity. An increasingly variable climate, however, is likely to make it difficult for hydropower plants to provide electricity consistently throughout the year. Dams are able to manage floodwaters which, given the region’s propensity for floods, works in their favour. At the same time, however, dams pose threats to the region. Large dams could be a contributory factor in generating destructive earthquakes and are at risk of failing after severe earthquakes, such a failure would be catastrophic for downstream communities. Clearly, the region’s leaders need to carefully consider the benefits and risks that widespread dam construction could bring to South Asia.

Any opinions or views expressed in this paper are those of the individual author, unless stated to be those of Future Directions International.

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