Surface Water Storage and Disasters

By: Sulagna Chattopadhyay
Ever since independence, dams were looked upon as the temples of modern India, our saviour against droughts, and partners in India’s development. However, ill-conceived structures devoid of environmental assessment and lack of upstream and downstream flow data have turned them into killers throughout the length and breadth of the country.
Planning n Mitigation

India is increasingly becoming an extreme weather event hotspot. From cold and heat waves to thunderstorms, hailstorms, dust storms, cyclones, droughts, floods and extreme rain episodes are causing heavy loss to life and property. Even dams, that were perceived as our saviours in preventing droughts and stemming floods, are emerging as killers—causing heavy erosion and sweeping off entire villages. Collapsing structures and the release of water from reservoirs during heavy rains have swept away many, with ensuing floods rotting away acres of crops. As per the Central Water Commission’s (CWC) ‘National Register of Large Dams’, India has 4857 large dams, with 314 under construction dams, above the height of 10 m, as per information last updated in 2014. Apart from these large structures, smaller, below 10 m reservoirs are in abundance, numbering well
over 20,000.

Dam failures and downstream flooding

India has a long history of dam failures. The Kaddam Project Dam, Adilabad, Andhra Pradesh, built in 1957-58, collapsed in the later half of 1958, as it was unable to hold flood waters that breached sections of the dam leading to its failure. The Kaila Dam, Kutch, Gujarat, constructed between 1952-55 collapsed in 1959. The Kodaganar Dam, Tamil Nadu, constructed in 1977 on a tributary of the Cauvery River, failed due to overtopping of flood waters. As the dam breached, an earthquake was also registered. The Nanaksagar Dam, Bhakra, Punjab, constructed in 1962 breached in 1967, due to heavy monsoon rains. The Panshet Dam, Ambi, Maharashtra was built in 1961 and failed the same year—the rain caused a rapid rise of the reservoir water level and the embankment was unable to bear the increased load. The Khadakwasla Dam, Mutha, Maharashtra built in 1879, collapsed in 1961 as a result of the breach that developed in the Panshet Dam upstream. The Tigra Dam, Sank, Madhya Pradesh was built in 1917 and collapsed the same year due to structural faults. In more recent time, in November 2009, the right bank of the Moolathara dam in the Palakkad district of Kerala was breached following the release of water from the Aliyar dam by Tamil Nadu. In 2010, more than a dozen villages were inundated in Gararda Dam in Bundi, Rajasthan after a newly constructed dam collapsed flooding houses and drowning livestock.

The Morvi disaster and recent tragedies

But by far the greatest dam disaster in the world happened in 1979 as the Machhu II Dam in Morvi, Rajkot, Gujarat, burst, killing an estimated 25,000 people. The rains arrived late; and once it did, pounded the town of Morvi for 10 consecutive days. Since the dam was not designed for such heavy rainfall, it burst, and submerged the entire town of Morvi, destroying all that came in its way—infrastructure, humans and animals. The enquiry that followed proved the government’s carelessness and inadequate planning. The dam was ill designed and when the investigations brought out facts that were too embarrassing for the government to face, the findings were reportedly concealed. It was only a few years ago, that access to documents revealed the actual extent of the tragedy. A book was consequently published by Utpal Sandesara and Tom Wooten ‘No one had a tongue to speak’, wherein the authors pointed out the carelessness of design and the lack of environmental assessment which led to the disaster.

Tragedies due to discharge of flood waters by dam personnel have recently been in the news. Last year, in June 2014, a group of 25 students on an excursion were swept away when the gates of the Larji hydroelectric project on the Beas in Himachal Pradesh were suddenly opened without warning. The tragedy was repeated in August, 2015 when floodwaters were released by officials from the Amakhal Dam on the Sukhmi river in Harda, Madhya Pradesh, killing 30 persons.

This year, heavy rains in August compelled the Damodar Valley Corporation (DVC) officials in Jharkhand to let out water from the Panchet and Maithon dams. Since West Bengal was already reeling under heavy rains due to cyclone Komen, and the effect of a spring tide, the waters from the dam swamped 12 districts, killing 83 people, damaging over seven lakh acres of standing crops.

Dam safety monitoring

Downstream flooding and other operational problems can be avoided if we understand the need for dam safety. Unfortunately, dam safety and its significance is hardly understood, and complications arising out of its negligence have rarely been documented. In fact, the National Disaster Management Authority (NDMA) was completely clueless about dam related disasters when G’nY posed dam safety related questions to them.

A dam safety programme comprises the designing, construction, operation and maintenance of a dam, along with regular surveillance, safety review, remedial action, education and training for emergency operations. The notion that once a dam is built and operational, only minor maintenance work will suffice is a fallacy. On the contrary, operation and maintenance of a dam should be a routinely organised activity based on sound engineering procedures and demands of the topography. In the lower reaches of the Ganga, high rate of siltation makes dredging an essential task. In the absence of adequate dredging, the dam loses its ability to hold enough water. In such a situation, opening of sluice gates becomes necessary, as happened this monsoon with the dams under the DVC. West Bengal Chief Minister Mamata Banerjee highlighted the inadequacies of the DVC and blamed its engineers for the calamity that befell the State.

The prime objective of a surveillance system is to analyse and present data on the dam and its environ in order to ensure adequate warning of any unsafe trends in the behaviour of the dam. This entails monitoring, alongside visual inspection, checking and testing of instrumentation followed by reporting and analysis of the data to understand the structural response to increased loads. Thus, dam safety covers structural as well as operational aspects. In the absence of these, tragedies like that befell the Macchu II at Morvi in 1979 cannot be averted.

Indian dams are mostly vulnerable to seismic hazards. This component is well tackled and  potential structural damages envisaged and safeguards ensured. But, post construction, the dam authorities are lackadaisical about the upkeep of the dams, as Himanshu Thakkar, Coordinator at South Asia Network on Dams, Rivers and People, pointed out to G’nY. “The Sardar Sarovar, the most talked about dam of the decade, has shoddy dam safety norms. Its stilling basin was damaged and 30 months elapsed before a meeting of the dam safety body could be organised.” Dam safety data, along with height of water, according to Thakkar should be real-time, and available online, with data archived for five years or more. Besides, every dam management committee should remain abreast of the operational information and meet at least once every quarter, in Thakkar’s opinion.

Inadequate environmental assessment can also be the cause of dams becoming unsafe, and putting regions around them at risk. The Koyna earthquake in 1967 was the result of building a dam on a seismically active zone that could not take the load of the water in the reservoir. This triggered an earthquake of intensity 6.5 on the Richter scale, that flattened Koynanagar town killing 180 people (injuring 1500 others) and destroyed the power house associated with the dam. Since then, 19 earthquakes of intensity greater than 5 have struck Koyna, till 2005. The 6.8 magnitude Tehri earthquake of 1991 has also been attributed to the then under-construction Tehri dam in Uttarakhand. Although the epicenter was slightly away from the site of the dam—which is claimed to be designed to withstand earthquakes of up to 8.4 magnitude, seismologists predict earthquakes of more than 8.5 intensity in this region in future. In case such an earthquake was to occur, a breach in the dam can expose thousands of people to massive floods.

At times, inadequate data or analyses of the hydro-geological parameters of a river can result in long-term environmental disasters too. The building of the Kosi embankment in Bihar has not only caused waterlogging of acres of fertile land, but also impoverished thousands of rural families, turning them into environmental refugees, as Dinesh Mishra has pointed out in his book, ‘Trapped between the devil and deep waters: The story of Bihar’s Kosi river,’ published by People’s Science Institute and South Asian Network on Dams, Rivers and People (SANDRP) in 2008.

The Farakka Barrage built in 1969 on the Indo-Bangladesh border is also another example of a similar folly. The barrage not only dammed the Ganga to hold back its waters, but plugged its distributaries—Kalindri, Pagla and Chhoto Bhagirathi, which had normally absorbed the outflow of the swollen Ganga in the past. This, along with the fact that the Ganga is heavily laden with silt, proved Farakka’s undoing. Heavy siltation has rendered 58 of the 109 sluice gates of the barrage defunct. As a result, following a heavy monsoon upstream in Uttar Pradesh or Bihar, the water flows downstream into Malda and Murshidabad, and swallows entire villages. Over the years, thousands of acres of fertile land, mango orchards and farms have been swept away, and more than three million people in Malda and Murshidabad districts are affected, with an estimated eight lakh people having been rendered homeless, as geographer Kalyan Rudra points out in his 2004 vernacular book, ‘Ganga bhangan katha: A fact-finding observation of Ganga river erosion in Malda and Murshidabad districts’.

In a paper presented in a 2002, Dam Safety Conference in Tampa, Florida, ‘Designing dam safety monitoring and early warning systems using failure modes analysis’, Barry K Myers has provided an outline on how advanced detection of dam health could lead to corrective action and timely intervention. To accomplish this, Myers feels, the monitoring system must be focused on detecting events that are precursors to failure. He recommends the failure modes analysis as a tool to understand events that could lead to dam failure, while recommending the use of automated instrumentation that can warn about dangers in time.

Thakkar, however, is not convinced that automated instruments and other dam safety provisions are enough. In his opinion, “an upstream and downstream flow pattern should be in place while taking a decision to release unprecedented amounts of water that can lead to flooding downstream.” He cites the 2006 Ukai case, when the dam released 11 lakh cusecs, following an extended period of rainfall, that submerged the city of Surat. “The downstream river is equipped to handle only 3 lakh cusecs, but the dam authorities initially released 6 lakh cusecs, and then 11 lakh cusecs, delaying release by waiting for orders that were to come from Gandhinagar, consequently flooding Surat”, he said.

Dam safety is however, not about the dam only. It is also about not allowing habitations to come up along flood plains downstream. Once a dam is constructed, people are under the impression that the river has been trained. Increases in the built-up area, construction in the floodplains, filling in of the riverbed and floodplains, silting up of the riverbed and construction of embankments, new bridges and weirs all contribute to reducing both the capacity of the river and the open space that allows floodwaters to spread out.

In a country where climate variability has always been difficult to cope with, increasing extreme weather events are exacerbating uncertainties. For a welfare state, people’s needs should be of utmost importance but at the same time implementation of safety mandates is equally important.

Legislatures and programmes

According to the CWC dam safety is an inherent function in the planning, design, construction, maintenance and operation of dams. It has been recognised that dam safety aspects, particularly of the existing dams, do not receive adequate attention even as the number of dams are aging.

Further, most of these dams were constructed using the standards and criteria prevalent at that time which may either not be safe under today’s river regimes or may not be acceptable in terms of safety to life and property. It has also been recognized internationally that a successful dam safety assurance programme requires a dedicated institutional structure with access to top management.

As per news reports, the National Democratic Alliance government is pushing for a national law on dam safety. The Bill had been introduced by the UPA II in 2010 but lapsed with the dissolution of the 15th Lok Sabha. With the private sector engaged in the construction of dams, it is perhaps imperative that such a Bill is reintroduced at the earliest. The plan behind such a dam safety bill is to create a mechanism for surveillance, inspection and operation of all dams to ensure their safe functioning. It may also seek to establish a national committee on dam safety. This will mean earmarking sufficient funds for maintenance and repair of specified dams, as also establishing disaster management and emergency action plans, besides a comprehensive dam safety evaluation every 5-10 years.

However, Thakkar rues, “the Bill is a closed club affair”, while calling for independent experts to make the bill process transparent. “Else, it is a redundant exercise”, he remarks.

A World -Bank assisted programme, the Dam Rehabilitation and Improvement Project (DRIP- India), approved in 2010, is currently underway in India. The objective of the project is “to improve the safety and operational performance of selected 223 existing dams at a cost of INR 2100 crore in four states—Kerala, Madhya Pradesh, Odisha and Tamil Nadu, with provision for taking up some more dams in other states in future”. The project is in line with an earlier World Bank assisted, Dam Safety Assurance and Rehabilitation Project (DSARP) implemented in 1991-99 at a cost of INR 422.95 crore.

“In India, a voice-based announcement system for flood/overflow intimation will further bolster the dam safety this time around”, L A V Nathan, chief engineer, Dam Safety Organisation, CWC, told G’nY.

However, activists like Thakkar do not set much in store as regards the present dam safety norms being followed. “In 2007, the Jaswant Sagar dam in Rajasthan, breached, creating havoc. It was one of the dams included in the World Bank aided safety project”. In his opinion, a new holistic regimen involving the right design, environmental assessment, and regular maintenance is the only worthwhile alternative to ensure safe and secure dams in future.

Endnote

With its wide network of rivers and growing demand for power and year-long water supplies, India needs dams and multi-purpose projects. But building dams is not the only solution; dam safety norms must be adhered to lest the dams meant to nurture life end up as killers. For this, an environmental impact assessment, followed by the right design in tune with the hydro-geological parameters involved, and regular maintenance of the dam is the only solution.

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