- By 2050, most people on Earth would be living downstream of tens of thousands of large dams built in the 20th century, many of them including India’s already operating at or beyond their design life, putting lives and property at risk.
- Besides India, other countries with reported aged dam cases include the US, France, Canada, Japan, Zambia and Zimbabwe.
- Large dam construction surged in the mid-20th century and peaked in the 1960s-70s, especially in Asia, Europe and North America, while in Africa the peak occurred in the 1980s.
- The number of newly constructed large dams after that continuously and progressively declined.
- However, the world is unlikely to witness another large dam building revolution as in the mid-20th century, but dams constructed then would inevitably be showing their age.
Ageing water infrastructure: An emerging global risk
- A recent report "Ageing water infrastructure: An emerging global risk" by United Nations University Institute for Water, Environment and Health (based in Canada) released in 2021 stated that most of the 58,700 large dams constructed worldwide between 1930 and 1970 which had a design life of around 50 to 100 yearswould most probably begin to express signs of ageing.
- The different ageing signs include:
- o increasing cases of dam failures
- o progressively increasing costs of dam repair and maintenance
- o increasing reservoir sedimentation
- o loss of dam's functionality and effectiveness
- The report additionally states that dams that were well designed, constructed and maintained could easily reach 100 years of service but it has been predicted that there could be an increase in "decommissioning", since economic and practical limitations could prevent ageing dams from being upgraded or if their original use could have now become obsolete.
- Lately, decommissioning has been gaining pace in the US and European nations.
Understanding the Basics
- Dam is defined as a barrier built across a stream, river or estuary to confine and check the flow of water for uses such as human consumption, irrigation, flood control and electric power generation.
- Lately, dams are considered more as hydropower generators while mitigation of flood, facilitation of irrigationand supply of drinking water, are considered only as additional benefits.
- A dam could be a central structure in a multipurpose scheme designed to conserve water resources on a regional basis.
- Multipurpose dams hold a special importance in developing countries, where a single dam might bring significant benefits related to hydroelectric power production, agricultural development, and industrial growth.
- However, dams have become a focus of environmental concern because of their impact on migrating fish and riparian ecosystems.
- In addition, large reservoirs could inundate vast tracts of land that are home to many people, and this has fostered opposition to dam projects by groups who question whether the benefits of proposed projects are worth the costs.
- Worldwide, the huge volume of water stored behind large dams is estimated at 7,000 to 8,300 cubic kilometres, enough to cover about 80 per cent of Canada's landmass under a metre of water.
Globally, about 2.2% of dams build before 1950 have failed mainly due to flooding, inadequate spillway capacity, bad workmanship etc.
Although India ranks third globally with above 5000 large dams in operation and about 500 under construction, India too has had its share of dam failures. There have been more than 36 reported failures cases so far. The major failure are as given below:
- The first failure was recorded in Madhya Pradesh in 1917 when the Tigra Dam failed due to overtopping.
- The worst dam disaster is, however, associated with the failure of Machu dam (Gujarat) in 1979 in which more than 2000 people died.
- Recently, the breach in Tiware dam in Maharashtra’s Konkan region swept away more than 20 people.
- What are the different Kinds of Dams?
- Diversion Dam - Like the name suggests, a diversion dam is used to divert water. They provide pressure to push water into ditches, canals, or other areas used for conveyance. Diversion dams are typically lower in height and have a small water storage area in its upstream.
- Buttress Dam - Buttress dams could take many forms, but they all consist of a sloping deck supported by intervals of buttresses. Buttress dams usually use less concrete than other dams but are not necessarily cheaper. There are three main buttress dams:
- multiple arch type
- massive head type
- deck type
- Embankment Dam - An embankment dam is a large, artificial dam that is constructed with natural excavated materials or industrial waste materials, such as compacted plastics, and various compositions of soil, sand, rock, and clay.
- Cofferdam - A cofferdam is a temporary, portable dam used for a variety of projects including bridge repair, shoreline restoration, pipeline installation, and many other construction projects.
- Storage Dam - These dams are not meant to divert or keep water out, but to keep water in. Storage dams are constructed to store water during the rainy seasons, supply water to the local wildlife, and store water for hydroelectric power generation, and irrigation. Storage dams are the most common types of dams.
- Detention Dam - Detention dams are specifically constructed for flood control by retarding flow downstream, helping reduce flash floods (to some extent).
- Gravity Dam - A gravity dam is a massive, man-made concrete dam designed to hold large volumes of water.
- What are the significances of Dams?
- The primary functions of dams are - water supply, irrigation, flood control, hydropower, and recreation.
- Dams supply the wealth of water to the parched fields of millions of farmers.
- They meet the domestic, municipal and industrial water needs of urban and rural areas.
- They form the backbone of India’s Power Grid Management since they generate cheap and eco-friendly hydro power across the country.
- Dams sustain the growth of flora and fauna in many of the degraded forests.
- Dams offer a viable solution for checking unsustainable depletion of ground water, which may be inching towards tripping point under the tremendous pressure created due to the growing population.
Issues associated with dam
- 32,716 large dams (55 per cent of the world's total) are found in just four Asian countries: China, India, Japan, and the South Korea, a majority of which will reach the 50 year threshold relatively soon.
- China has 23,841 large dams (40 per cent of the world's total).
- The same is true for many large dams in Africa, South America and Eastern Europe.
- Rising maintenance expense: There is the increasing risk of older dams, the rising maintenance expense, the declining functionality of dams due to sedimentation, and the societal impacts. However, the problem of ageing large dams today confronts only a relatively small number of countries, 93 per cent of the world's large dams being located in just 25 nations.The nature of these impacts could vary significantly between low and high income countries.
- Fragmented pattern: However, the pace of large dam construction has dropped dramatically in the last four decades and continues to decline in part because the best locations for such dams globally have been progressively diminishing as around 50 per cent of the global river volume is already fragmented or regulated by dams.
- Environmental and social impact: Furthermore, there are strong concerns regarding the environmental and social impacts of dams, and large dams in particular, as well as emerging ideas and practices on the alternative types of water storage, nature-based solutions, and types of energy production beyond hydropower.
- Decommissioning: Public safety, escalating maintenance costs, reservoir sedimentation, and restoration of a natural river ecosystem have become the major reasons behind dam decommissioning. Decommissioning would also have various positive and negative economic, social, and ecological impacts to be considered in the local and regional social, economic, and geographic context. It could be critical to protect the broader, sustainable development objectives for a region.
- Disadvantages of dam construction
There are numerous advantages of building a dam and that is the reason why a government invests so much money in the construction and maintenance of Dams. But there are certain disadvantages related to it:
- Expensive affair: Building a dam is very expensive and the government needs to ensure that strict guidelines are followed and a very high standard is maintained. The dams must operate for many years in order to become profitable enough to compensate for the high building cost.
- Chances of flooding: People residing in villages and towns in the nearby area, where there are chances of flooding, have to be relocated.
- Loss of land and livelihood: They lose their businesses and farm lands.
- Forced removal: Sometimes people are removed forcibly to set up hydro-power plant and it poses a serious ethical concern.
- Geological damage: The building of large dams can cause serious changes to the earth’s surface and lead to geological damage. It could trigger frequent earthquakes. However, modern planning and design of dams have reduced the possibility of occurrences of certain disasters.
- Acceleration of ageing process: Climate change would accelerate the dam ageing process. Further, the rising frequency and severity of flooding and other extreme environmental events could overwhelm a dam's design limits and accelerate a dam's ageing process.
- Siltation of reservoir is a serious issue, though in most cases the extent of siltation continues to remain unknown. De-siltation of reservoir is difficult in many a cases owing to environmental concerns related to sediment disposal.
Consequences of Ageing Dams
Ageing dams could be associated with a number of deleterious and long-term consequences:
- Impact on Food Security:When soil replaces the water in reservoirs, supply gets choked. Consequently, the cropped area may begin receiving less and less water as time progresses.As a result, the net sown water area either shrinks in size or depends on rains and groundwater(which ultimately gets over-exploited).
- Impact on Farmers’ Income:Since water is a crucial factor for crop yield and credit, crop insurance, and investment, crop yield may get affected severely, andcould disrupt the farmer’s income.
- Increased Flooding:The flawed siltation rates reinforce the argument that the designed flood cushion within several reservoirs across many river basins may have already depleted substantially, due to which floods have become more frequent downstream of dams.
- The flooding of Bharuch in 2020, Kerala in 2018, and Chennai in 2015 are a few examples attributed to downstream releases from reservoirs.
Dam Safety in India
- More than 75% of the country’s dams are over 25 years old and about 164 dams are more than 100 years old.
- Over 1,115 large dams that will be roughly 50 years old in 2025
- more than 4,250 large dams in the country will be over 50 years old in 2050
- 64 large dams will be more than 150 years old in 2050
- These pose growing threat.
- For example: Approximately 3.5 million people are at risk if India’s Mullaperiyar dam in Kerala, built over 100 years ago, “were to fail”. The dam, in a seismically active area, shows significant structural flaws and its management is a contentious issue between Kerala and Tamil Nadu States.
- Many dams have varied structural deficiencies and shortcomings in operation and monitoring facilities, while few do not meet the present design standard- both structurally as well as hydrologically.
- With the increasing number of dams becoming older and older, dam failures are more expected now.
- Additionally, most of the States have been failing to provide sufficient budgets for maintenance and repair of the dam.
- Many States also lack the institutional and technical capacities for addressing dam safety issues.
- Need of Dam Safety in India
- Dams are critical infrastructure developed for irrigation, power generation, flood moderation and supply of water for drinking and industrial use. As such their safety has serious consequences for human life, ecology and public and private assets and a matter of great concern to the general public and becomes a national responsibility to take necessary steps to ensure it.
- Ensuring Dam Safety is essential for safeguarding huge investments in infrastructure.
- Correspondingly, it is also crucial for safeguarding human life, and livelihoods of the people living downstream of the dams.
Dam Safety Framework in India
- National Committee on Dam Safety (NCDS) –
- Establishment: It was constituted by Government of India in 1987.
- Chaired by: It is chaired by Chairman, Central Water Commission and is represented by all the States having significant number of large dams and other dam owning organizations.
- Objective: NCDS suggests ways to bring dam safety activities in line with the latest state of the art consistent with the Indian conditions and acts as a forum for exchange of views on techniques adopted for remedial measures to relieve distress in old dams.
- Central Dam Safety Organization (CDSO) –
- Establishment: It was established under Central Water Commission in 1979.
- Objective: The objectives of Central Dam Safety Organization are:
- Assist in identifying the causes of potential distress
- Perform a coordinative and advisory role for the State Governments
- Lay down guidelines, compile technical literature, organize trainings, etc.
- create awareness in the states about dam safety
- State Dam Safety Organizations (SDSO)-
- They are Dam Safety Organization/Cell established in eighteen States and four dam owning organizations (NHPC, BBMB, DVC and Kerala State Electricity Board).
- Routine Periodic Inspections are done by trained and experienced engineers from Dam Safety Organization at least twice a year(pre monsoon and post monsoon).
- It incorporates examination of the general health of the dam and appurtenant works. Additionally, preparedness of dam and hydro mechanical structures for handling expected floods is estimated.
- Correspondingly, Comprehensive Dam Safety Evaluation is carried out once in a decade and is a more comprehensive examination.
- It includes a multi-disciplinary team for holistic view and may order additional field and laboratory investigations as well as numerical simulations.
Challenges in the current framework
- The current legal framework does not have any provision for penalizing the owner in case of a dam failure causing a disaster in the upstream or downstream of the dam.
- The lack of systematic assessment and monitoring coupled with inadequate resources is the primary cause of poor maintenance of dams and appurtenant works.
- The real time inflow forecasting systems are not in place even in important reservoirs. Such systems could add to dam safety measures besides improving operational efficiencies.
- The procedure requires that revision study of dam hydrology needs to be completed much in advance of any rehabilitation exercise but this not being the case has led to delays in DRIP implementation.
- Dam design drawings or drawings as constructed are not available with project authorities in many cases. Dam Safety Organizations in states is short of adequate man power and need to be strengthened.
- Dam Rehabilitation and Improvement Project (DRIP) –
- Ministry of Water Resources, River Development & Ganga Rejuvenation through Central Water Commission, in 2012, launched the six year Dam Rehabilitation and Improvement Project (DRIP) with the World Bank to improve the safety and operational performance of selected dams, along with institutional strengthening with system wide management approach.
- In 2018, the government approved the extension of DRIP Project for two more years with the revised scheduled closure in June 2020.
- Recently, the Cabinet Committee on Economic Affairs, chaired by the Prime Minister, has approved the Dam Rehabilitation and Improvement Project (DRIP) Phase II and Phase III.
- It envisages comprehensive rehabilitation of 736 existing dams located across the country and complements the Dam Safety Bill, 2019.
- The Implementation Period for Phase II and III isover a period of 10 years from April 2021 to March 2031, in two phases of six years duration with two years overlapping.
- Dam Safety Bill 2019 - A Bill seeking to set up an institutional mechanism for surveillance, inspection, operation and maintenance of specified dams across the country was passed by the Lok Sabha in 2019.
- The provisions of the Bill were proposed to be applied to all dams in the country which have a height of more than 15 metres, or between 10 metres to 15 metres.
- Among other things, the Bill also seeks to resolve the inter-state issues concerning maintenance and safety of dams as around 92% of dams in the country are on inter-state river basins.
- Further, the Bill provides for the institutional mechanism to ensure the safety of such dams including creation of National Committee on Dam Safety, National Dam Safety Authority, and State Dam Safety Organisation.
- The owners of the specified dams are required to provide a dam safety unit in each dam.
- The Bill also provides punishment for offences.
- Dam Health And Rehabilitation Monitoring Application (DHARMA) - It is web-based software package to support the effective collection and management of Dam Safety data in respect of all large dams of India. The software is designed for users at Central, State and Dam level, with user permission rights governed by their respective licenses.
- Seismic Hazard Mapping along with development of Seismic Hazard Assessment Information System (SHAISYS) - It is also web based interactive application tool being developed in Central Water Commission under Dam Safety Organisation to estimate the seismic hazard at any point in Indian region. The SHAISYS shall be capable of estimating seismic hazard using the deterministic as well as probabilistic approach.
- Other Initiatives– Other important activities include Design Flood Review, publication of important Guidelines as well as Manuals dealing with Dam Safety Management, preparation of operation and maintenance Manuals, Emergency Action Plans,
- Attract Global Attention:There is a need to attract global attention to the issue of ageing water storage infrastructure and stimulate international efforts.
- Sustainable Decommissioning:Decommissioning would have various positive and negative economic, social, and ecological impacts to be considered in a local and regional social, economic, and geographic context which are critical to protect the broader, sustainable development objectives for a region.
- Transparency in Information:India’s water organizations have to be more transparent concerning dysfunctional and deteriorating large dams.Thus, real-time information on the live storage capacity of large storage structures should be made available.A realistic estimate of the country’s irrigation potential needs to be made based on this for proper planning and management of available water.
- Alternative Measures:Water policymakers, planners, and water managers need to think of alternative plans for large storage structures. Some alternatives include: selecting sites for construction of water harvesting structures of varying capacities; building medium or minor irrigation-based small storage structures;and identifying mechanisms to recharge aquifers and store water underground.
A Standing Committee Report has recommended that a penal provision for dam failures should be incorporated in the law and compensation should be provided to the affected families.Latest technologies should be adopted not only at the time of constructing the dam, but also during periodic review of the dams.Institutional Capacity building is needed in design flood estimation and flood routing for most of the states.A well planned monitoring system based on data collection and evaluation using modern instrumentation is the key to early detection of defects and ageing scenarios.
Rehabilitationof old dams using the latest materials and technologies can enhance the life of a dam for many more decades.India will eventually feel difficulty in finding sufficient water in the 21st century to feed the rising population by 2050, grow abundant crops, create sustainable cities, or ensure growth. Therefore, all stakeholders must come together to address this situation urgently.