Is age catching up with India’s dams?

“At Independence, the brand new Authorities of India … made the constructing of huge dams a central a part of its technique for reworking India, a dedication to which it adhered for many years,” historian Daniel Klingensmith wrote in his 2007 e-book ‘One Valley and a Thousand’.

The Damodar Valley Company, 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 change into “a means by which the modernity and value of the nation could possibly be enhanced, examined, and displayed.”

At this time, nonetheless, India faces the problem of enormous components of its hydrological infrastructure ageing en masse. In line with the Nationwide Register of Giant (Specified) Dams, some 1,065 have been 50-100 years outdated and 224 have been greater than a century outdated in 2023.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 phases of their initially supposed lifespan, elevating security and efficiency considerations that transcend issues of engineering alone.

In follow, India’s dam tasks have sometimes assumed a helpful life on the order of some many years. The Bhakra Dam accomplished in 1963 was anticipated to serve for at the very least 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 Decrease 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 many years 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 ‘local weather load’ is factored in. Dams greater than 50 years outdated immediately have outdated spillway capacities and structural security components and require pressing consideration to make sure they’ll proceed to operate safely.

Modes of failure

Dams’ a number of failure modes might be cut up into three sorts: structural, hydraulic, and geotechnical. These modes are arduous to pry aside in follow nevertheless it’s helpful to deal with them individually if solely to establish particular methods to surmount them.

A structural failure is when a dam ruptures or collapses because of weaknesses implicit to its construction. Widespread causes embrace poor design and/or development, materials degradation, and structural parts being pressured to resist forces they weren’t geared up to. For instance, progressive concrete deterioration can weaken a concrete dam over time. A technique this occurs is when silica in rocky aggregates within the construction reacts with alkali compounds within the cement to kind a water-absorbing substance. Because the substance expands, the concrete begins to crack from inside. This class additionally consists of 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 perfect identified explanation for this mode, particularly within the period of local weather change, is overtopping: when flood waters move over the dam’s pinnacle, doubtlessly breaching the construction en route. When influx exceeds the dam’s capability, inadequate spillway capability or blocked spillways also can result in overtopping. Equally, when a dam’s outflow could be very quick, it may well erode the construction’s downstream face, additionally leading to hydraulic failure.

In earth and rock-filled dam failures worldwide, overtopping has been the only commonest trigger (a few third of the time). India’s first recorded dam failure, of the Tigra Dam in 1917, was additionally because of overtopping, and general this trigger has been the primary one in many of the 36 recorded dam failures within the nation.

Lastly, a geotechnical failure happens when the dam’s foundations, abutments or the supplies inside the dam are unstable. Inside erosion within the basis has accounted for about 29% of masonry dam failures worldwide. Earth-fill dams are notably vulnerable to flawed piping within the dam’s physique, the place water can seep by the dam or its basis and ultimately trigger a breach.

Earthquakes and landslides also can set off structural in addition to geotechnical failures. Dams in seismically lively zones are notably weak 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 started to build up hydrostatic strain, elevating fears of a breach.

Actual-world failures are a mix of those modes. An preliminary structural deficiency might 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 leads to 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 most probably to change into evident. However as dams age, delayed upkeep, materials ageing, and unanticipated flooding or seismic occasions can dramatically enhance failure danger. In spite of everything, 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 tasks to make sure dam security, led by the security regime established by the Dam Security Act 2021. The instrument gives a framework to surveil, examine, function, and keep all specified giant dams, and requires institutional mechanisms at each the Central and the State ranges to uphold it.

On the Act’s coronary heart is the Nationwide Committee on Dam Security, the apex physique with the accountability of evolving dam security insurance policies and reviewing the work of State-level companies. The Committee is joined by the Nationwide Dam Security Authority (NDSA), a regulatory physique underneath the Union Jal Shakti Ministry tasked with implementing coverage and resolving interstate disputes.

On this situation, each State with giant dams is required to ascertain a State Dam Security 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 homeowners — 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 gives for remedial actions that SDSOs can order if a dam is discovered to be falling brief.

Earlier than the Act, the Central Water Fee (CWC) had set tips for dam homeowners on common upkeep and security critiques. To this finish, many States have had Dam Security Evaluate Panels: skilled teams sometimes populated by skilled dam engineers, hydrologists, and geologists and which audit ageing dams and suggest rehabilitation measures. The Dam Security 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 also be subjected to particular inspections.

In 2012, the Indian authorities mooted the flagship Dam Rehabilitation and Enchancment Venture (DRIP) to improve ageing dams. DRIP locations explicit emphasis on capability constructing, together with coaching State dam engineers in modern security practices and growing au courant emergency motion plans. Upgraded dams consequently have piezometers, inclinometers, and seismic displays on website waiting for 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.
| Picture Credit score:
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, enhancing drainage and filtration methods in earth dams, changing gates and valves, putting in trendy sensors and devices, and enhancing operational processes. The federal government authorized DRIP phases II and III in 2020 to cowl 736 dams in 19 States, with monetary help from the World Financial institution and the Asian Infrastructure Funding Financial institution for bodily rehabilitation and to undertake complete security evaluations. As of early 2024, critiques for greater than 400 dams had reportedly been accomplished.

Dovetailing on DRIP are tips to cope with the results of pure occasions rendered extra intense and/or frequent by local weather change. This consists of rechecking the possible most flood for spillway designs, enhancing 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 bolstered concrete overlays. The Nationwide Hydrology Venture and flood forecasting initiatives have additionally been working to enhance flood administration upstream.

On the flip aspect, 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 Security Act empowers authorities to declare a dam unsafe and doubtlessly cease its operation, however there’s no process to decommission it altogether. Specialists have really helpful India develop a risk-based framework, i.e. when a dam’s failure danger exceeds acceptable limits and it’s now not possible to strengthen it.

Calls by specialists to decommission particular dams, such because the Mullaperiyar, have so far solely been handled in courts.

Economics of ageing

As a dam ages, the price of its repairs rises. Older dams usually require structural strengthening, e.g. by retrofitting their spillways or reinforcing concrete; upgrading gates and mechanical gear; and repeatedly dredging and managing sediment.

Second, the lack of reservoir capability because of siltation diminishes water provide, irrigation potential, and hydroelectric energy era capability. Addressing sedimentation by dredging and restoring catchment areas, amongst different measures, can also be costly. At one level, the Authorities of India had deemed the Bhakra reservoir’s large-scale dredging to be “cost-prohibitive”.

To guage the potential price of an entire failure, analysts use danger evaluation fashions that think about the chance of failure along with its penalties. In follow, a dam’s hazard classification (low, important or excessive) relies on the worst penalties ought to it fail. Consequence evaluation frameworks, such because the one the US’s Division of Homeland Safety makes use of to evaluate dam security, enumerate the results in three classes: human (populations in danger, potential lack of life), financial (property injury, infrastructure loss, price of substitute and remediation), and important 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 era or water provide as a part of enterprise losses. Relying on the related guidelines, the evaluation might also embrace intangible prices like environmental injury and long-term financial setback to the area.

India presently makes restricted formal calls for of financial analyses of dam failures. Earlier than the federal government approves a dam, the venture proponent is required to submit an environmental influence evaluation (EIA) that features a dam failure evaluation. Since 2021, the Dam Security Act has required sure dams to have emergency motion plans and inundation maps on file. However the authorities has additionally been progressively weakening EIA governance, together with approving tasks sans EIAs and permitting defaulters to pay a wonderful and proceed offending ones.

Maybe 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 folks (though some estimates go as much as 20,000). The failure additionally demolished most of Morbi city. Extra just lately, the Tiware Dam in Ratnagiri district of Maharashtra failed in 2019, wiping out total villages and killing 19 folks.

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 international locations 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 invention drew requires older dams to have their security margins reviewed by unbiased 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 precise excessive prices. Whereas 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 direction of risk-based decision-making, which implies vouchsafing investments for dams that pose the very best danger, which in flip is a operate of the probability of failure and the magnitude of downstream penalties. Such an method 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

Maybe the easiest way 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.
| Picture Credit score:
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 supposed lifespan was round six many years. It’s positioned in Kerala however Tamil Nadu owns and operates it to help agriculture downstream, and this shared nature has precipitated a long-standing dispute over the construction’s integrity.

Mullaperiyar lies in a seismically lively 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 by the dam was mitigated for a time, however many specialists nonetheless think about Mullaperiyar to be weak. The dam’s spillway capability is restricted relative to present possible most flood estimates and thus faces a better overtopping danger.

A UN College report revealed in 2021 estimated that if the dam have been to break down, round 35 lakh folks could be in danger and the monetary prices could also be tens of hundreds of crores (in rupees).

In 2014, the Supreme Court docket put collectively an Empowered Committee that discovered the dam to be typically safer at decrease water ranges however which nonetheless really helpful 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 in the end liable for implementing the Supreme Court docket’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.
| Picture Credit score:
ANI

Commissioned in 1957, the Hirakud Dam in Odisha is among the many first post-Independence river valley tasks in addition to one of many longest earthen dams on the earth, stretching 25.8 km (together with dykes). It types a colossal reservoir on the Mahanadi River and has been essential for flood management, coastal irrigation, and producing hydroelectric energy. However virtually seven many years 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 capability 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 ability continued to ship down heavy sediment masses. In a detailed 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 revealed by the CWC highlighted a must replace flood routing and improve spillway capability.

As for geotechnical security: Hirakud’s prodigious size means repeatedly sustaining its earthen sections, together with to forestall slope failures and management seepage, is important. The Authorities 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 predicted to inundate greater than 11,000 sq. km of land and have an effect on hundreds of thousands of individuals.

Whereas the authorities haven’t reported any instant structural crimson flags, the actual fact stays that the dam is 63 years outdated. In 2023, the Nationwide Human Rights Fee even responded to public anxiousness and inquired into Hirakud’s security standing after heavy monsoon rains. The federal government’s method has been to strengthen Hirakud by repairing its spillways and including monitoring methods. Decommissioning has been out of the query given its financial worth. The dam is thus an ageing however crucial one which should be diligently managed to forestall any failure, particularly as pure stresses accumulate.

Lastly, let’s think about 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 constructed with the unrelenting toil of man for the advantage of mankind”. Bhakra is a sturdy concrete gravity dam, which issues as a result of India has but to document a concrete dam failure so far — however this doesn’t imply the dam can by no means fail.

It faces important age-related considerations, mainly (and by this level familiarly), reservoir sedimentation and outdated design requirements. The Sutlej River it straddles carries a excessive silt mass because of real-estate growth and landslides within the Himalaya. By 2020 or so, investigations by the Bhakra Beas Administration 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 might significantly shorten that. In structural phrases, Bhakra is taken into account well-designed nevertheless it additionally wants seismic reanalyses to make sure its stability underneath 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 presently deem unlikely — could 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 fancy problem on the intersection of engineering, economics, and public coverage. Greater than 4,200 giant dams in India will cross the 50-year mark by 2050 and dam security will loom bigger than it does immediately — but every ageing dam has distinctive danger components that have to be addressed individually. With local weather change progressively intensifying hydrological extremes, India’s dam security efforts should additionally incorporate forward-looking local weather resilience.

Specializing in dams that pose the best danger 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