“At Independence, the new Government of India … made the building of big dams a central part of its strategy for transforming India, a commitment to which it adhered for decades,” historian Daniel Klingensmith wrote in his 2007 ebook ‘One Valley and a Thousand’.
The Damodar Valley Corporation, the Bhakra Nangal, and the Hirakud within the Forties have been adopted by dams on the Rihand, Koyna, Tungabhadra, Chambal, and Krishna rivers within the decade after. In reality, within the 20 years from 1951, India had began work on 418 giant dams and by 2000 had accomplished round 4,000. In Klingensmith’s telling, constructing dams had develop into “a way by which the modernity and worth of the nation could be enhanced, tested, and displayed.”
Today, nevertheless, India faces the problem of huge components of its hydrological infrastructure ageing en masse. According to the National Register of Large (Specified) Dams, some 1,065 have been 50-100 years outdated and 224 have been greater than a century outdated in 2023. Many main dams of the post-1950 interval are actually within the final levels of their initially meant lifespan, elevating security and efficiency issues that transcend issues of engineering alone.
In apply, India’s dam initiatives have sometimes assumed a helpful life on the order of some a long time. The Bhakra Dam accomplished in 1963 was anticipated to serve for a minimum of 100 years as a reservoir however its builders underestimated sedimentation charges, a lot in order that the reservoir’s capability had dropped by practically 25% within the first 35 years of its use. Likewise, the Lower Bhavani Dam in Tamil Nadu had misplaced 28% of its capability between 1956 and 2005 and the Nizam Sagar Dam had misplaced roughly half its capability simply within the first three a long time of use since 1931.
These examples illustrate one reality clearly: the preliminary design lifetime of many dams isn’t equal to the precise life. The price of operating a dam at its authentic efficiency ranges can shoot up because it ages — and that is earlier than the extra ‘climate load’ is factored in. Dams greater than 50 years outdated right this moment have outdated spillway capacities and structural security components and require pressing consideration to make sure they will proceed to perform safely.
Modes of failure
This {photograph} reveals buildings close to the Arbaat Dam, 40 km north of Port Sudan, after it collapsed following heavy rains and torrential floods on August 25, 2024.
| Photo Credit:
AFP
Dams’ a number of failure modes may be cut up into three sorts: structural, hydraulic, and geotechnical. These modes are onerous to pry aside in apply but it surely’s helpful to deal with them individually if solely to determine particular methods to surmount them.
A structural failure is when a dam ruptures or collapses on account of weaknesses implicit to its construction. Common causes embrace poor design and/or development, materials degradation, and structural elements being compelled to face up to forces they weren’t outfitted to. For instance, progressive concrete deterioration can weaken a concrete dam over time. One means this occurs is when silica in rocky aggregates within the construction reacts with alkali compounds within the cement to type a water-absorbing substance. As the substance expands, the concrete begins to crack from inside. This class additionally contains structural cracks, slope instability in earth embankments, and gate and sluice failures.
Worldwide, about 42% of concrete dam failures have been attributed to foundational and structural points. Structural failures in Indian dams have been traced to seepage, corroded piping, and/or weak foundations.
A hydraulic failure happens when the dam can now not safely retailer water. The finest recognized reason behind this mode, particularly within the period of local weather change, is overtopping: when flood waters cross over the dam’s pinnacle, probably breaching the construction en route. When influx exceeds the dam’s capability, inadequate spillway capability or blocked spillways may result in overtopping. Similarly, when a dam’s outflow may be very quick, it will possibly erode the construction’s downstream face, additionally leading to hydraulic failure.
In earth and rock-filled dam failures worldwide, overtopping has been the one commonest trigger (a couple of third of the time). India’s first recorded dam failure, of the Tigra Dam in 1917, was additionally on account of overtopping, and general this trigger has been the primary one in many of the 36 recorded dam failures within the nation.
Finally, a geotechnical failure happens when the dam’s foundations, abutments or the supplies inside the dam are unstable. Internal erosion within the basis has accounted for about 29% of masonry dam failures worldwide. Earth-fill dams are notably prone to flawed piping within the dam’s physique, the place water can seep via the dam or its basis and ultimately trigger a breach.
Earthquakes and landslides may set off structural in addition to geotechnical failures. Dams in seismically energetic zones are notably susceptible to quake-induced cracking or slope failures. When the magnitude-6.6 Koynanagar earthquake in Maharashtra shook the Koyna Dam in 1967, the construction developed cracks and commenced to build up hydrostatic stress, elevating fears of a breach.
Real-world failures are a mixture of those modes. An preliminary structural deficiency may result in extreme leaks (geotechnical failure) that weaken the dam. Thus when the a part of the river upstream of the dam receives heavy rainfall or when there’s a glacial lake outburst flood (just like the one which roiled Sikkim in 2023), the waters overtop the dam and ends in a catastrophic breach.
The world’s historical past of dams signifies greater than 70% of failures happen within the first decade of operations as that is when flaws within the design or development are probably to develop into evident. But as dams age, delayed upkeep, materials ageing, and unanticipated flooding or seismic occasions can dramatically improve failure threat. After all, as local weather change intensifies, it will increase the danger of pure disasters of unprecedented magnitude — and to not have precedent means to lose historical past as a information.
Caring for older dams
India’s Central and State governments have developed an evolving framework of insurance policies, legal guidelines, and initiatives to make sure dam security, led by the security regime established by the Dam Safety Act 2021. The instrument supplies a framework to surveil, examine, function, and preserve all specified giant dams, and requires institutional mechanisms at each the Central and the State ranges to uphold it.
At the Act’s coronary heart is the National Committee on Dam Safety, the apex physique with the duty of evolving dam security insurance policies and reviewing the work of State-level companies. The Committee is joined by the National Dam Safety Authority (NDSA), a regulatory physique beneath the Union Jal Shakti Ministry tasked with implementing coverage and resolving interstate disputes.
In this situation, each State with giant dams is required to ascertain a State Dam Safety Organisation (SDSO) headed by certified engineers to supervise dams in its jurisdiction. (If a dam is positioned in a single State however operated by one other, the NDSA supplants the related SDSO.)
The 2021 Act additionally specifies common inspection schedules. Dam house owners — usually a State’s irrigation division or energy utility — are required to conduct pre-monsoon and post-monsoon checks yearly, amongst others. The legislation additionally requires every dam to have an emergency motion plan and an alarm system, and supplies for remedial actions that SDSOs can order if a dam is discovered to be falling quick.
Before the Act, the Central Water Commission (CWC) had set pointers for dam house owners on common upkeep and security opinions. To this finish, many States have had Dam Safety Review Panels: knowledgeable teams sometimes populated by skilled dam engineers, hydrologists, and geologists and which audit ageing dams and advocate rehabilitation measures. The Dam Safety Organisation inside the CWC additionally maintains a database of dam incidents and assists States in investigative research. After any main pure catastrophe, a dam can be subjected to particular inspections.
In 2012, the Indian authorities mooted the flagship Dam Rehabilitation and Improvement Project (DRIP) to improve ageing dams. DRIP locations specific emphasis on capability constructing, together with coaching State dam engineers in up to date security practices and creating au courant emergency motion plans. Upgraded dams because of this have piezometers, inclinometers, and seismic displays on web site expecting indicators of misery. These in flip additionally require dam well being monitoring software program to be built-in with dams’ operations and for every dam to take care of a log, like its report card.
Jawaharlal Nehru inspects the Bhakra Dam on a go to to Chandigarh, 1959.
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The Hindu
From 2012 to 2021, DRIP I rehabilitated 198 dams in Jharkhand, Karnataka, Kerala, Madhya Pradesh, Odisha, Tamil Nadu, and Uttarakhand. Work included grouting cracks, strengthening spillway piers, bettering drainage and filtration programs in earth dams, changing gates and valves, putting in trendy sensors and devices, and bettering operational processes. The authorities accepted DRIP phases II and III in 2020 to cowl 736 dams in 19 States, with monetary help from the World Bank and the Asian Infrastructure Investment Bank for bodily rehabilitation and to undertake complete security evaluations. As of early 2024, opinions for greater than 400 dams had reportedly been accomplished.
Dovetailing on DRIP are pointers to deal with the results of pure occasions rendered extra intense and/or frequent by local weather change. This contains rechecking the possible most flood for spillway designs, bettering spillway capability, and including auxiliary channels. Older masonry and concrete dams are additionally evaluated in opposition to present earthquake codes and strengthened if required by anchoring, buttressing or including strengthened concrete overlays. The National Hydrology Project and flood forecasting initiatives have additionally been working to enhance flood administration upstream.
On the flip facet, DRIP doesn’t make room for dams to be decommissioned; as an alternative it focuses on extending the lifespan of dams in any respect prices. India the truth is lacks an official dam decommissioning coverage. The Dam Safety Act empowers authorities to declare a dam unsafe and probably cease its operation, however there’s no process to decommission it altogether. Experts have beneficial India develop a risk-based framework, i.e. when a dam’s failure threat exceeds acceptable limits and it’s now not possible to strengthen it.
Calls by specialists to decommission particular dams, such because the Mullaperiyar, have to this point solely been dealt with in courts.
Economics of ageing
As a dam ages, the price of its maintenance rises. Older dams usually require structural strengthening, e.g. by retrofitting their spillways or reinforcing concrete; upgrading gates and mechanical tools; and constantly dredging and managing sediment.
Second, the lack of reservoir capability due to siltation diminishes water provide, irrigation potential, and hydroelectric energy technology capability. Addressing sedimentation by dredging and restoring catchment areas, amongst different measures, can be costly. At one level, the Government of India had deemed the Bhakra reservoir’s large-scale dredging to be “cost-prohibitive”.
To consider the potential price of an entire failure, analysts use threat evaluation fashions that contemplate the chance of failure collectively with its penalties. In apply, a dam’s hazard classification (low, vital or excessive) relies on the worst penalties ought to it fail. Consequence evaluation frameworks, such because the one the US’s Department of Homeland Security makes use of to evaluate dam security, enumerate the results in three classes: human (populations in danger, potential lack of life), financial (property harm, infrastructure loss, price of substitute and remediation), and significant providers (lack of water provide, energy, irrigation).
Thus, a complete failure situation evaluation would possibly estimate the asset substitute price of the dam and its related buildings, the remediation price for downstream cleanup, and the misplaced energy technology or water provide as a part of enterprise losses. Depending on the related guidelines, the evaluation might also embrace intangible prices like environmental harm and long-term financial setback to the area.
India at the moment makes restricted formal calls for of financial analyses of dam failures. Before the federal government approves a dam, the venture proponent is required to submit an environmental impression evaluation (EIA) that features a dam failure evaluation. Since 2021, the Dam Safety Act has required sure dams to have emergency motion plans and inundation maps on file. But the federal government has additionally been progressively weakening EIA governance, together with approving initiatives sans EIAs and permitting defaulters to pay a fantastic and proceed offending ones.
Perhaps the worst failure in India’s historical past was the collapse of the Machchu-II Dam in Morbi in Gujarat in 1979. This earthen dam was constructed within the Seventies and was breached after excessive rainfall. Water spilled from the dam in a flash flood that killed greater than 2,000 individuals (though some estimates go up to twenty,000). The failure additionally demolished most of Morbi city. More just lately, the Tiware Dam in Ratnagiri district of Maharashtra failed in 2019, wiping out total villages and killing 19 individuals.
Following tropical cyclone Daniel, the Derna and the Abu Mansour Dams in Libya collapsed in September 2023 and killed greater than 3,800. The incident prompted nations worldwide to double-check their very own dams — and thus the Himachal Pradesh authorities discovered 21 dams within the State had violated their security norms, together with possessing insufficient spillways. The discovery drew requires older dams to have their security margins reviewed by impartial specialists.
Dam failures additionally impose long-term prices as native governments have to revive broken transport hyperlinks, compensate and rehabilitate the affected households, and reverse losses in agricultural productiveness. Even near-miss occasions can actual excessive prices. While the 2018 floods strained however didn’t breach a number of dams in Kerala, the State’s financial system was hit by the emergency reservoir drawdowns and managed downstream spilling it needed to impact.
This mentioned, financial evaluations of dam security are actually shifting in the direction of risk-based decision-making, which suggests vouchsafing investments for dams that pose the very best threat, which in flip is a perform of the probability of failure and the magnitude of downstream penalties. Such an strategy helps guarantee restricted funds are directed to averting essentially the most extreme potential disasters, even when the limitedness is arguably synthetic and never inevitable.
Three talismans
Perhaps one of the best ways to contextualise these measures and insurance policies is to learn them within the context of three of India’s nice outdated dams (subjectively talking): the Mullaperiyar, the Hirakud, and the Bhakra Nangal. They’re not the one high-risk dams, in fact, however they rank among the many most distinguished for his or her age, dimension, and significance.
Water gushing out from the Mullaperiyar Dam close to Thekkady in Kerala, November 18, 2021.
| Photo Credit:
The Hindu
The Mullaperiyar Dam on the Periyar River was accomplished in 1895 as a 53.6-m excessive masonry gravity dam. The British colonial administration constructed it with lime surkhi (powdered burnt clay) mortar. Its meant lifespan was round six a long time. It’s positioned in Kerala however Tamil Nadu owns and operates it to assist agriculture downstream, and this shared nature has precipitated a long-standing dispute over the construction’s integrity.
Mullaperiyar lies in a seismically energetic area on the fringe of the Western Ghats and has developed leaks and cracks over time. The construction was bolstered within the Seventies and the amount of water flowing via the dam was mitigated for a time, however many specialists nonetheless contemplate Mullaperiyar to be susceptible. The dam’s spillway capability is proscribed relative to present possible most flood estimates and thus faces a better overtopping threat.
A UN University report printed in 2021 estimated that if the dam have been to break down, round 35 lakh individuals can be in danger and the monetary prices could also be tens of 1000’s of crores (in rupees).
In 2014, the Supreme Court put collectively an Empowered Committee that discovered the dam to be usually safer at decrease water ranges however which nonetheless beneficial ongoing oversight. (The NDSA hadn’t taken form by 2022 so on the time the Centre had made the Chief Secretaries of the 2 States finally chargeable for implementing the Supreme Court’s situations.) Kerala has since stepped up calls for to construct a brand new dam to interchange Mullaperiyar whereas Tamil Nadu has insisted it may be operated safely with steady upkeep.
A truck passes over a bridge whereas floodwater of the Mahanadi river is launched from the Hirakud Dam.
| Photo Credit:
ANI
Commissioned in 1957, the Hirakud Dam in Odisha is among the many first post-Independence river valley initiatives in addition to one of many longest earthen dams on the earth, stretching 25.8 km (together with dykes). It varieties a colossal reservoir on the Mahanadi River and has been essential for flood management, coastal irrigation, and producing hydroelectric energy. But virtually seven a long time on, Hirakud additionally typifies the challenges posed by giant, ageing earth-fill dams.
Its security relies on its huge embankments, masonry spillway, sedimentation charges, and its capacity to deal with floods. Even by the Nineteen Eighties, Hirakud’s reservoir had misplaced roughly 1 / 4 of its storage to silt whereas deforestation upstream of the power continued to ship down heavy sediment hundreds. In an in depth name in 1982, excessive influx virtually overtopped the dam, forcing operators to chop open an auxiliary spillway. With high-rainfall occasions proliferating within the area, a 2016 case examine on the dam’s local weather resilience printed by the CWC highlighted a must replace flood routing and improve spillway capability.
As for geotechnical security: Hirakud’s prodigious size means constantly sustaining its earthen sections, together with to stop slope failures and management seepage, is important. The Government of Odisha and the CWC have of late undertaken intensive evaluations, together with analysing its sluice gates for stress and seismic security. Densely populated areas, together with Cuttack metropolis, lie downstream of the dam. A failure occasion is anticipated to inundate greater than 11,000 sq. km of land and have an effect on thousands and thousands of individuals.
While the authorities haven’t reported any instant structural purple flags, the very fact stays that the dam is 63 years outdated. In 2023, the National Human Rights Commission even responded to public anxiousness and inquired into Hirakud’s security standing after heavy monsoon rains. The authorities’s strategy has been to strengthen Hirakud by repairing its spillways and including monitoring programs. Decommissioning has been out of the query given its financial worth. The dam is thus an ageing however crucial one which have to be diligently managed to stop any failure, particularly as pure stresses accumulate.
Finally, let’s contemplate the 62-year-old Bhakra Nangal Dam, a 226-m excessive construction, creator of the Gobindsagar reservoir, and a veritable linchpin of North India’s water provide panorama. Jawaharlal Nehru famously known as it a construction “worthy of worship” for having “been built with the unrelenting toil of man for the benefit of mankind”. Bhakra is a strong concrete gravity dam, which issues as a result of India has but to file a concrete dam failure up to now — however this doesn’t imply the dam can by no means fail.
It faces vital age-related issues, mainly (and by this level familiarly), reservoir sedimentation and outdated design requirements. The Sutlej River it straddles carries a excessive silt mass due to real-estate improvement and landslides within the Himalaya. By 2020 or so, investigations by the Bhakra Beas Management Board (BBMB) had additionally revealed sediment deposits had shaved off 23% of the reservoir’s gross capability.
The dam was anticipated to be efficient for 100 years however officers have warned that the reservoir’s dropping capability may significantly shorten that. In structural phrases, Bhakra is taken into account well-designed but it surely additionally wants seismic reanalyses to make sure its stability beneath bigger earthquakes and periodic checks of its spillway gates and powerhouse. (The spillways have been designed for flood estimates drafted within the mid-Twentieth century.)
Downstream of the dam, Bhakra serves Punjab’s agricultural heartland and several other main cities. A hypothetical failure — which specialists at the moment deem unlikely — can be catastrophic and so Bhakra stays a high-consequence construction. To its credit score, the BBMB has additionally undertaken intensive catchment reforestation programmes to curb silt influx and is exploring choices to divert sediment elsewhere.
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Taken collectively, India’s ageing dams current a posh problem on the intersection of engineering, economics, and public coverage. More than 4,200 giant dams in India will cross the 50-year mark by 2050 and dam security will loom bigger than it does right this moment — but every ageing dam has distinctive threat components that should be addressed individually. With local weather change progressively intensifying hydrological extremes, India’s dam security efforts should additionally incorporate forward-looking local weather resilience.
Focusing on dams that pose the best threat and addressing their points with state-of-the-art options and, crucially, in session with downstream communities ought to thus be a nationwide precedence.
mukunth.v@thehindu.co.in
