Dams are large water storage infrastructures that are mainly used to produce electricity but the purpose is not limited to the production of hydroelectricity, because the reservoirs created by dams are also used for flood control, irrigation, human consumption, industrial use, aquaculture etc. Hence, dams are critical infrastructures for the development of a nation in several ways such as water, power, irrigation etc. For any nation, the construction of dams is a very big project that directly affects the nation’s economy due to its design. Dams are used to secure water for future purposes, however, a report by United Nations University Institute for Water, Environment and Health, released in January has raised the alarm of risk on global security.
According to the report, “Ageing Water Infrastructure: An Emerging Global Risk”, released by Canada based United Nations University, which aims to analyse the infrastructural integrity of dams across the world that have surpassed 50 years and are posing greater safety risk and higher cost of maintenance The report has analysed the factors, figures and the impact on local livelihood, nature, and economy of the country due to ‘mass ageing’ of water storage infrastructures and includes case studies of dams in countries like USA, France, Canada, India, Japan, Zambia and Zimbabwe. The report further discusses the practice of decommissioning dams in the USA and Europe and the socio-economic impacts on the culture, heritage, local lives, property value etc.
In the report which “aims to attract global attention to the creeping issue of ageing water storage infrastructure and stimulate international efforts to deal with this emerging water risk,” as stated by co-author and Director of UNU-INWEH, most of the large dams worldwide have been built between 1930-1970 bearing a design life of 50-100 years and many of them are working beyond their intended lifespans. There are about 58,700 dams across the globe that have reached the threshold of “50 years” while 100s of these dams, which will soon approach 100 years, are posing a global threat to the environment and human safety. The revolution of dam construction, which took place from 1960 to 1970, will inevitably show the age and defectiveness of dams in the upcoming years. However, is it likely that the world will not witness the revolution of dam construction again and “the number of newly-constructed large dams after that continuously and progressively declined?” The reason is the best-suited location for the construction of these dams which have been diminishing since the past decade and the dams across the world have already captured 50% of the global river volume.
By 2050, most people on Earth will live downstream of tens of thousands of large dams, built in the 20th century, many of them already operating at or beyond their design life because of the reason that at 50 years, a large concrete dam “would most probably begin to express signs of ageing.”- a UN report says.
The report has contended that climate change is a major catalyst in the ageing process. Conditions like rising frequency, the severity of flooding and other extreme conditions are some of the climate-change factors.
“Underlined is the fact that the rising frequency and severity of flooding and other extreme environmental events can overwhelm a dam’s design limits and accelerate a dam’s ageing process. Decisions about decommissioning, therefore, needs to be taken in the context of a changing climate
Although the authors of the report, Duminda Perera and Vladimir Smakhtin, have made it clear that 50 years is not the defining age as the structural defects may arise at any stage. Though 50 years is an “arbitrary age” for critical infrastructures like dams, it may start showing the signs of ageing “such as decay or deterioration of the structural materials used in construction, ageing of other components such as gates and spillways, and sedimentation (when silt settles at the bottom over time, reducing the dam's storage capacity)”. The ageing factor also depends upon the construction and maintenance, and excellently engineered and properly maintained dams could last up to hundreds or thousands of years and the International Commission on Large Dams has recommended certain practices which can be carefully implemented for the dams that are being built today so that they could work properly for generations.
“This problem of ageing large dams today confronts a relatively small number of countries - 93% of all the world’s large dams are located in just 25 nations.”-suggests the report.
As per the report, China accounts for almost 40% of all the large dams in the world with 23,841 large dams built in the country which is followed by the USA and India. “Out of 32,716 large dams (55% of the world's total) found in just four Asian countries: China, India, Japan, and South Korea a majority will reach the 50-year threshold relatively soon”. The same will happen with large dams of other countries like Africa, South America and Eastern Europe. However, the studies are more threatening and concerning for India as “the average age of Indian dams is 42 years, which is much younger in comparison to some of the other leading countries”.
The report further explains the factors of ageing includes cases of dam failures, progressively increasing costs of dam repair and maintenance, increasing reservoir sedimentation, and loss of a dam’s functionality and effectiveness - a “strongly interconnected” manifestation.
The report also provides information that how the cost of maintenance increases and the functionality of the dams incredibly decreases due to sedimentation. Along with the risks and impacts of ageing dams, the report seeks to provide measures such as decommissioning of dams and working on alternative water storage solutions that can be looked upon by the policymakers.
The case analyzes the database of the International Commission on Large Dams (ICOLD) which defines the criteria for categorizing the dams into large and small. According to ICOLD those dams which are 15+ meters in height when measured from the lowest foundation to crest or 5 to 15 meters high impounding more than 3 million cubic meters capacity are listed as large dams. Out of all large dams, roughly one in eight has a 100 million cubic meter capacity.
● The US has a total of 90,580 dams (all sizes) and the average age is estimated to be 56 years.
● Out of the total dams, more than 85% of the structures in 2020 are operating at or beyond their design life while Canada has over 50% of its large dams which have been constructed more than 50 years ago.
● 21 states of the country have removed 1275 dames in the last 30 years with the number being 80 in 2017 alone.
● Out of all dams, failures in the USA, 75% occurred after 50 years of age and the estimated cost of refurbishing the dams is US$64 billion.
China and the USA collectively account for 56% of the world’s large dams and China alone has 40% of all large dams in the world with the number in figures being 23,841 which is also 60% of the proportion in Asia.
Japan and UK:
The average age of large dams in Japan and the UK is over 100 years. About 10% of the large dams in Europe have turned 100+ years old.
The country generates 65% of its clean energy from hydropower. Australia has 650 dams and half of which are 50+ years old. More than 50 dams have been serving for more than 100 years now.
India: Figures and Concerns
With its release, the report has triggered an alarm for India as the authors have stated that the average age of Indian dams is 42 years which is much less as compared to other nations.
According to the report, India has 4,407 large dams out of which over 1,115 will turn 50 by 2050. Over 425+ dams will be over 50 years old in 2050 and 64 large dams will turn more than 150 years of age in 2050. This means that around 80% of the dams are on the verge of becoming obsolete putting both life and property at risk, as they are turning older ranging from 50 years to 150 years.
Although the figure of large dams in India as per the report has been taken as per the ICOLD’s registry of large dams and definition of “large dams” was modified in 2018. However, According to the Ministry's Jal Shakti Central Water Commission, the number of large dams is 5,334. Hence, the report seeks to consider only those dams which are listed in the large dam categories, as per the International norms.
If we consider the report of the Jal Shakti Ministry, 239 big dams in the country are over 100 years old.
As the report talks about only large dams, it can be reckoned by this study that the same will be the situation in the case of small dams as well, one can even consider it to be more disastrous.
There are hundreds of thousands of small and minor dams in the country which are much older than the large dams. Like, the Krishna Raja Sagar dam built-in 1931 is of 90 years now and the Mettur dam is now 87 years old. The situation is more horrifying as their life is even lower than that of large dams.
This report has cited the threat that surrounds 3.5 million people who are living around the Mullaperiyar Dam which is 126 years old and was declared unsafe by Kerala Government for passing the probable maximum flood limit. Nowhere in the report has any other dam been mentioned which shows the seriousness and high risk that the folks in the surrounding area face. Report points out various structural flaws and its situation is more contending due to it being a seismically active area which is situated in Zone III and is a high hazard dam, as notified by the Central Water Commission.
The majority of Indian dams are earthen built. Such dams are built by compressing successive layers of earth, and not the concrete due to which they are prone to ageing. Also, the accumulation of silt and debris behind the reservoir over the year reduces the storage capacity. The actual siltation is much higher as to what has been estimated. Additionally, flooding is one major reason which has caused 44% of dam failures in India and the remaining were caused by factors like, inadequate spillway capacity, piping, and poor workmanship, as per the Central Water Commission.
India is a land of farmers and the majority of farmers across the country are dependent on the waters supplied by dams to irrigate their fields. Over siltation leads to a reduction in water supply over time. Water is a very crucial factor for crop production, crop insurance and crop investment, but with the reduction in water supply, not only the crop production will be reduced but also the quality of the crop will be highly affected. This will directly affect the farmers, reducing their income.
Decommissioning of Dams: The only feasible way?
The report suggests the process of decommissioning as a solution to avoid the risk that is hanging over the heads of millions of lives, and billions of monetary loss that will result due to the ageing of dams. “Public safety, escalating maintenance costs, reservoir sedimentation, and restoration of a natural river ecosystem are among the reasons driving dam decommissioning” and “overall, dam decommissioning should be seen as equally important as dam building in the overall planning process on water storage infrastructure developments.” - the report suggests.
Decommissioning is a process of removal or demolition of dams and letting the river flow in its natural course. However, it is not an easy process because even the removal process takes years or even decades with continuous expert and public involvement and lengthy regulatory reviews. Apart from the positive impacts, various socio-economic impacts are to be considered as the cost of decommissioning depends on various site-specific factors such as the treatment of accumulated reservoir sediments, stream restoration, and the loss of operational benefits such as flood control, water supply, power etc. Besides this public risk, environmental factors are also involved that should be taken into consideration. However, dams decommissioned according to the report to date have been small, and removal of large dams “still in its infancy, with only a few known cases in the last decade”
The report has mentioned that none of the countries has any framework or protocols to guide the process of dam removal, and with the mass ageing of the dams altogether, a framework on national as well as international guidelines regarding the same is the need of the hour.
Project of dam removal, especially those which pose a greater safety risk, should be carried out in a phased manner by listing all the risks involved and the frequency of risk on humans, livestock, economy etc. Proper study should be done for each dam and report should be prepared dams-wise and not collectively at once to make sure which step should be more feasible, whether decommissioning or refurbishment.
For India, every river has multiple dams along its course, hence a cumulative assessment of every upstream and downstream dam should be done to ensure its safety. The nation does not have any properly drafted laws for dams, their construction, maintenance and liabilities. In 2019, the Dam Safety Bill was passed by the Lok Sabha and is yet to be passed by the Upper House to become an Act. The bill seeks to set up institutional mechanisms by setting up the National Dam Safety Authority for surveillance, maintenance, inspection and operation of dams that have heights of more than 15 meters, or between 10 to 15 meters, across the country. The main task of the authority would be to implement policies of the National Committee on Dams Safety and to resolve inter-state issues concerning maintenance and safety of dams.
In this era, where we are already moving towards scarcity of water and depletion of groundwater, other studies have suggested that available water will be insufficient to feed the growing population, crop production and other works to ensure development by 2050, where the groundwater and drinking water reports are already frightening, the ageing of dams is a matter of concern which all the nation especially India should take into consideration very seriously. All the stakeholders should come forward to address this issue by adopting preventive measures to avoid dam failures in the upcoming years.