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Raising of the Kotmale dam – misconceptions and facts



By Asoka Herath

BSc (Geology Hons); MSc (Engineering Geology), CEng.

Over the past few months, there has been considerable interests among not only geoscientists and engineers but also ordinary people in the potential risks faced by two of the major hydropower projects constructed in the central highlands, namely the Victoria and Kotmale projects. These projects have come into the limelight owing to some minor seismic tremors felt in the Victoria area, together with the recent announcement of the intention to raise the Kotmale dam. Alarm bells are ringing that seismic activity may jeopardize the integrity of the Victoria dam and the raising of Kotmale may result in dam failure. Should these dams fail, they will be the biggest manmade disasters our country has ever faced. This risk has prompted suggestions from the people higher up that we should seek advice from foreign experts.

Various opinions from the leading geoscientists of the country, regarding the causes and effects of this unusual activity were aired through the media recently. Some have attributed the seismic tremors to limestone quarrying in the Victoria reservoir area, some as the result of neo-tectonic movements of the central highlands, yet some others said they are reservoir-induced earthquakes. Those who are interested in the fundamentals of such activity may find the presentation in this link useful (

The intention of this article is to provide an insight into the geotechnical issues that influence the Kotmale Project, the risks, and to address some misconceptions people may have regarding the project. I take the liberty of writing on these issues as a person who has an in-depth knowledge of the Project by working from the site investigation phase through to construction completion, the later years as the Senior Engineering Geologist, leading the project geoscientist team.


The Project

Kotmale was meant to be the main upstream storage reservoir under the Mahaweli development scheme launched in the 1960s. It will regulate the Mahaweli waters, while providing a substantial energy component. The capacity of the reservoir will be more than doubled by the proposed raising of the dam, approximately by 30 m. The project was inaugurated in 1979 and funded by Sweden. Sir William Halcrow and Partners of UK (Halcrow) with Central Engineering Consultancy Bureau of Sri Lanka (CECB) was the design engineer and Skanska of Sweden was the contractor.


Geology of the Project Area

To understand the project risks, it is essential to understand the geology and structure of the project area. The area is underlain by Pre-Cambrian age metamorphic rocks comprising predominantly of two rock types, charnokite (gneiss) and crystalline limestone (dolomite or marble) with minor quartzites. The limestone is sandwiched between layers of charnokite gneiss.

The rock units are folded into a gentle anticlinorium (an arch like structure-convex shape) which has a slight plunge downstream. The axis of the anticline trends northwest and falls on the right abutment in the dam area. As such the dam foundation rocks have a slight inclination (15°-25°) downstream and into the abutments.

Charnokite is a very strong resistant rock, which does not breakdown easily while limestone deteriorates and erodes more easily. The initial site investigation drilling in the Kotmale valley found limestone thickness varied from 20 m to 130 m within the project area.

The limestone consists mainly of calcium carbonate (CaCO3) and partly magnesian carbonate (MgCO3). Carbonates dissolves in acidic water (acid rain) and forms solution cavities. These cavities have the potential to create leaks from the reservoirs.


Formation of the Kotmale Valley

The Kotmale valley is an amphitheatre-like valley reshaped by the erosional activity of the Kotmale Oya for millennia. It is approximately 5 km wide at the widest point, is surrounded by high rock cliffs up to 300 m high on both flanks, which converge at the Kadadora village; the site of the dam construction. The valley forming process was a combination of differential weathering and erosion of the underlying limestone unit, resulting in the collapse of overlying more resistant rock units. The basal slopes of the cliffs consist of accumulated debris of rocks and soil derived from the cliffs (termed as scree or talus). Historically these talus slopes were in perpetual slow motion (creep) towards the river. They were subjected to numerous landslides, typically during or after heavy rain events. Generally, the Kotmale valley was infamous for landslide activity.


History of Kotmale Project investigations

The location of the dam site had been selected for the seemingly favourable topography formed by the converging valley flanks. One of the first jobs assigned to me when I joined the CECB in 1978 as a young engineering geologist, was to map four exploratory tunnels driven into the abutments of the proposed dam and report the rock conditions. Our evaluation indicated the left abutment had very poor rock conditions not suitable for a dam foundation.

In 1979, to evaluate the landslide risk to the project, Halcrow carried out a landslide survey of the project area. This survey was done due to the frequent landslide activity in the Kothmale area, and its similarities to the Vajont Dam disaster that occurred in Italy in 1963, which wiped out several downstream towns resulting about 2500 deaths.

This study identified the left abutment as a settled block (subsided en mass); limestone solution the likely cause. It strongly recommended to move the damsite downstream and monitor the impressive cliffs on the left flank of the valley for potential movements.


Evaluation by a panel of experts

As these findings were major issues impacting the viability of the Project, the Mahaweli Authority of Sri Lanka as the owner of the project, in early 1980 engaged a panel of foreign experts who were the leaders in the fields of rock and soil mechanics, to evaluate the potential issues and provide recommendations. This panel endorsed the relocation of the damsite.

Subsequently, the dam axis was moved approximately 200 m downstream from the original location.


Nature and distribution of the limestone

At the new location, the limestone was at a much greater depth below the dam foundation compared to the original site as shown in Figure 1. Even so, solution cavities were observed in the contact zone and within the limestone itself identified by drilling and close circuit television (CCTV) inspections carried out in the drillholes. Our best estimate indicated small cavities, however a drillhole represents only a small area, therefore the existence of larger cavities could not be ruled out.


Leakage through cavernous limestone is widespread from the reservoirs built in our hill country. The Samanalawewa Project is the best example where significant leakage had been occurring through a cavernous limestone under the right abutment since the impoundment, which could not be sealed.


Continuity of the Kotmale limestone

Investigations were carried out to establish the continuity of the Kotmale limestone to downstream areas in view of potential leakage which were inconclusive. The recent geological map for the Kandy-Nuwara-Eliya districts (GSMB), I am convinced that the Kotmale limestone continues to Gampola-Atabage Valley and further to the Victoria Reservoir as a major rock unit. The limestone quarrying in the Victoria Reservoir area occurs in the same unit, which caused the recent furore about seismic events allegedly caused by blasting. Whilst I do not believe there is (or will be) significant leakage from Kotmale Reservoir, future raising of the dam may enhance leakage if it exists which needs evaluation.


Water tightness of the dam foundation

To eliminate the risk of water leakage through the limestone under the dam foundation, it was extensively grouted from a grouting gallery constructed below the dam level (see Figure 1). Generally, the grout intakes were low. Nevertheless, few holes required significant amounts of grout before they could be sealed. Subsequent water pressure testing indicated the limestone unit was properly sealed and the foundation was watertight.


Monitoring of the cliffs and other landslides

During the initial impoundment, the cliffs were inspected by walkover surveys and by periodic monitoring with geodetic surveying. Movements of any significance, precursor of an impending major failure were not recorded during the early years after construction.


Reservoir Induced Seismicity (RIS)

One important consideration in the construction of large reservoirs is the potential for reservoir induced seismicity (RIS). RIS is the incidence of earthquakes triggered due to the impoundment of water behind a dam. A simplistic explanation is that reservoirs trigger earth tremors due to the load of water which could activate otherwise dormant faults, the energy released causing earth tremors.

Halcrow decided to investigate the risk of movement of some major structures present in the Kotmale reservoir area upon impoundment, which could potentially induce seismic events. Consequently, a micro-seismic monitoring network (MSMN) consisting of four monitoring stations was established around Kotmale project in 1981. The monitoring program was managed by the CECB and continued until the early 90s.

Published data (Fernando & Kulasinghe 1985) show that the maximum event recorded at Kotmale during the first two and half years of monitoring, was an event of 2.25 magnitude (Richter Scale), located far away from the project area. The monitoring led to the conclusion that the potential for RIS at Kotmale was extremely low or non-existent. However, in view of the recent seismic events recorded around Victoria, it will be prudent to revisit the monitoring records from the Kotmale network, presumably archived by the CECB.


Potential risks from future raising

The Kotmale project infrastructure, were designed and constructed for future raising. Theraised dam simply achieves the original vision of the project, as the main upstream storage reservoir and increases power output.


In my opinion the geotechnical risks arising from the raising of the Kotmale dam are as follows:

= The raised water level in the reservoir will fully inundate the scree slopes and reach the base of the left bank cliffs with potential to create major landslides. Cliff monitoring should be re-established using modern methods such as satellite based synthetic aperture radar interferometry (inSAR).

= There is potential for leakage through the limestone with raised water levels. All evidence suggests the limestone under the dam was properly sealed. Leakage from the reservoir flanks cannot be prevented, which is not a fatal flaw to the project. Requirement for abutment sealing should be revisited.

= It will be useful to re-establish the monitoring program of stream gauging in the Gampola-Atabage valley to investigate if any leakage will occur from Kotmale to Atabage valley. This should be initiated before the dam raising.

= All evidence points to reservoir induced seismicity is a non-issue for Kotmale Project.


Finally, I strongly advocate the raising of the dam for the following reasons:


= The original project infrastructure was developed with the intention of future raising.

= There are potential risks but not fatal flaws to the viability of the Project. These risks can be mitigated.

= People were evacuated from their ancestral lands going under the reservoir and if the project is not completed as originally intended, then this relocation of people was without merit and a grave injustice to them.

= The country unnecessarily lost approximately 30 MW of power for more than 35 years.


The potential risks with the raising of the Kotmale dam discussed here need to be evaluated, and if the need arise, they should be mitigated and managed using local expertise. In my opinion, what Sri Lanka lacks is good project managers vital in successful implementation of projects of such enormous national importance. In hindsight, the Kotmale reservoir should have been built to the full capacity at the first instance.


(The author currently works as a Principal Geotechnical Engineer with AMC Consultants Pty Ltd, Perth, Australia, and can be contacted at


Foreign policy dilemmas increase for the big and small



‘No responsible American President can remain silent when basic human rights are violated.’ This pronouncement by US President Joe Biden should be interpreted as meaning that the supporting of human rights everywhere will be a fundamental focus of US foreign policy. Accordingly, not only the cause of the Armenians of old but the situation of the Muslim Uyghurs of China will be principal concerns for the Biden administration.

However, the challenge before the US would be take this policy stance to its logical conclusion. For example, the murder of Saudi journalist Jamal Khashoggi was one of the most heinous crimes to be committed by a state in recent times but what does the Biden administration intend to do by way of ensuring that the criminals and collaborators of the crime are brought to justice? In other words, how tough will the US get with the Saudi rulers?

Likewise, what course of action would the US take to alleviate the alleged repression being meted out to the Uyghurs of China? How does it intend to take the Chinese state to task? Equally importantly, what will the US do to make light the lot of Russian opposition leader Alexei Navalny? These are among the most urgent posers facing the US in the global human rights context.

Worse dilemmas await the US in Africa. Reports indicate that that the IS and the Taliban have begun to infiltrate West Africa in a major way, since they have been compelled to vacate the Middle East, specially Syria and Iraq. West African countries, such as, Mali, Burkina Faso, Nigeria and Mauritania are already facing the IS/Taliban blight. The latter or their proxies are in the process heaping horrendous suffering on the civilian populations concerned. How is the US intending to alleviate the cruelties being visited on these population groups. Their rights are of the first importance. If the US intends to project itself as a defender of rights everywhere, what policy program does it have in store for Africa in this connection?

It does not follow from the foregoing that issues of a kindred kind would not be confronting the US in other continents. For example, not all is well in Asia in the rights context. With the possible exception of India, very serious problems relating to democratic development bedevil most Asian states, including, of course, Sri Lanka. The task before any country laying claims to democratic credentials is to further the rights of its citizens while ensuring that they are recipients of equitable growth. As a foremost champion of fundamental rights globally, it would be up to the US to help foster democratic development in the countries concerned. And it would need to do so with an even hand. It cannot be selective in this undertaking of the first importance.

The US would also from now on need to think long and deep before involving itself militarily in a conflict-ridden Southern country. Right now it is up against a policy dilemma in Afghanistan. It is in the process of pulling out of the country after 20 years but it is leaving behind a country with veritably no future. It is leaving Afghanistan at the mercy of the Taliban once again and the commentator is right in saying that the US did not achieve much by way of bringing relief to the Afghan people.

However, the Biden administration has done somewhat well in other areas of state concern by launching a $1.9 trillion national economic and social resuscitation program, which, if effectively implemented could help the US people in a major way. The administration is also living up to the people’s hopes by getting under way an anti-Covid-19 vaccination program for senior US citizens. These ventures smack of social democracy to a degree.

The smaller countries of South Asia in particular ought to be facing their fair share of foreign policy quandaries in the wake of some of these developments. India, the number one power of the region, is in the throes of a major health crisis deriving from the pandemic but it is expected to rebound economically in an exceptional way and dominate the regional economic landscape sooner rather than later.

For example, the ADB predicts India will recover from an 8% contraction in fiscal 2020 and grow by 11% and 7% this year and next year. South Asia is expected to experience a 9.5% overall economic expansion this year but it is India that will be the chief contributor to this growth. A major factor in India’s economic fortunes will be the US’ stimulus package that will make available to India a major export market.

For the smaller states of South Asia, such as Sri Lanka, the above situation poses major foreign policy implications. While conducting cordial and fruitful relations with China is of major importance for them, they would need to ensure that their relations with India remain unruffled. This is on account of their dependence on India in a number of areas of national importance. Since India is the predominant economic power in the region, these smaller states would do well to ensure that their economic links with India continue without interruption. In fact, they may need to upgrade their economic ties with India, considering the huge economic presence of the latter. A pragmatic foreign policy is called for since our biggest neighbour’s presence just cannot be ignored.

The Sri Lankan state has reiterated its commitment to an ‘independent foreign policy’ and this is the way to go but Sri Lanka would be committing a major policy mistake by tying itself to China too closely in the military field. This would send ‘the wrong signal’ to India which is likely to be highly sensitive to the goings-on in its neighbourhood which, for it, have major security implications. A pragmatic course is best.

In terms of pragmatism, the Maldives are forging ahead, may be, in a more exceptional manner than her neighbours. Recently, she forged closer security cooperation with the US and for the Maldives this was the right way to go because the move served her national interest. And for any state, the national interest ought to be of supreme importance.

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A Sri Lankan centre for infective disease control and prevention



The need of the hour:

BY Dr B. J. C. Perera

MBBS(Cey), DCH(Cey), DCH(Eng), MD(Paed), MRCP(UK), FRCP(Edin), FRCP(Lon), FRCPCH(UK), FSLCPaed, FCCP, Hony FRCPCH(UK), Hony. FCGP(SL)

Specialist Consultant Paediatrician and Honorary Senior Fellow, Postgraduate Institute of Medicine, University of Colombo, Sri Lanka.

On 01st July 1946, the Communicable Disease Center (CDC) of the United States of America opened its doors and occupied one floor of a small building in Atlanta, Georgia. Its primary mission was simple, yet highly challenging. It was to prevent malaria from spreading across the nation. Armed with a budget of only 10 million US dollars, and fewer than 400 employees, the agency’s early tasks included obtaining enough trucks, sprayers, and shovels necessary to wage war on mosquitoes.

It later advanced, slightly changed its name, and transformed itself into the much-acclaimed and reputed Centres for Disease Control and Prevention (CDC). It became a unique agency with an exceptional mission. They work 24/7 to protect the safety, health and security of America from threats there and around the world. Highest standards of science are maintained in this institution. CDC is the nation’s leading science-based, data-driven, service organization that protects the public’s health. For more than 70 years, they have put science into action to help children stay healthy so they can grow and learn, to help families, businesses, and communities fight disease and stay strong and to protect the health of the general public. Their are a bold promise to the nation, and even the world. With this strategic framework, CDC commits to save American lives by securing global health and America’s preparedness, eliminating disease, and ending epidemics. In a landmark move, the CDC even established a Central Asia regional office at the U.S. Consulate in Kazakhstan in 1995 and have been involved in public health initiatives in that region.

More recently, the European Centre for Disease Prevention and Control (ECDC), was established. It is an agency of the European Union, aimed at strengthening Europe’s defences against infectious diseases. The core functions cover a wide spectrum of activities such as surveillance, epidemic intelligence, response, scientific advice, microbiology, preparedness, public health training, international relations, health communication, and the scientific journal Eurosurveillance.

Still later on, the African CDC (ACDC) was born. It strengthens the capacity and capability of Africa’s public health institutions, as well as partnerships, to detect and respond quickly and effectively to disease threats and outbreaks, based on data-driven interventions and programmes.

All these organisations are autonomous, independent, and are confidently dedicated to hold science to be sacred. They play a major role in advocacy and work in a committed advisory capacity. With the cataclysmic effects of the current coronavirus pandemic COVID-19, the contributions made by these institutions are priceless. What is quite important is that they are able to provide specific recommendations based on the latest scientific information available for countries and nations in their regions, even taking into account the many considerations that are explicit and even unique to their regions. All these organisations have been provided with optimal facilities and human resources. The real value of their contribution is related to just one phenomenon: AUTONOMY.

Well…, isn’t it the time for us to start a Sri Lankan Centre for Infective Disease Control and Prevention (SLCIDC)? It should be formulated as an agency constantly striving, day in and day out, to safeguard the health of the public. Science and unbending commitment to evaluation of research on a given topic should be their operating mantra. It would work as a completely apolitical organisation and what we can recommend is that it would be directly under the President of the Democratic Socialist Republic of Sri Lanka, unswervingly reporting to and accountable to the President. It would consist of medical doctors, scientists and researchers but no politicians of any sort, no non-medical or non-scientist persons, no hangers on and no business persons. All appointments to the SLCIDC will be made by the President of the country, perhaps in consultation with medical professional organisations.

The prime duty of the SLCIDC would be to assess the on-going situation of any infective issue that has any effect on the health of the public. The organisation will undertake in-depth examination and assessment of a given situation caused by an infective organism. They need to have all relevant data from within the country as well as from outside the country. There will not be any vacillation of the opinions expressed by them and their considered views should not be coloured by any consideration apart from science and research done locally and worldwide. Their considered opinion would be conveyed directly to the President of the country. They are free to issue statements to keep the public informed about the results of their deliberations.

We believe that it would be a step in the right direction; perhaps even a giant step for our nation, not only during the current coronavirus pandemic but also on any major problems of an infective nature that might occur in the future.


This writer wishes to acknowledge a colleague, a Consultant Physician, who first mooted this idea during a friendly conversation.

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Kudurai Madiri Pona



The big jumbo has come from the French land and as the French themselves say it is ‘annus mirabillis’ the miracle year, finally, and finally the wait is over. The world will now see the Big- Bus that we all waited for so long to see. As the years roll by, none would talk of delays regarding the delays on delivery dates and how late the bird flew in. These would be like words written on a blackboard, erased forever. But the aeroplane will grace the sky and, perhaps rewrite all the records of commercial aviation when the mega-miracle A380 dominates the international air-routes.

Singapore Airlines went into the record books as the launch customer. Some of my old friends from SIA would fly the A380. Perhaps, Luke would, too, and this story is about him. Luke of yesteryear and how he first flew as a cadet and how young Luke and I went romping the skies in our own special way, writing a few new lines in the flight training manual.

Luke was from Johor Baru, in Malaysia. His roots were in South India where years ago his grandfather had done a Robinson Crusoe and ended up in the Malayan Peninsula. Luke was named after one of the four Gospel scribes. Luke really isn’t his name. It is a pseudonym, I use just to give him some anonymity. Not much protection, but one is to three are playable odds. Like in Rumple stiltskin the manikin, you are welcome to guess the name.

We first flew to Seoul. He, straight out of flying College, and yours truly, as old as the hills, driving the ‘Jumbo’ classic, the lovable 747. The first thing I noticed about him was his socks, black and white diamond shapes, a mini version of the flags they swing at Grand Prix finals – if Luke swung his feet, a Ferrari would pass underneath. That we sorted out the first day itself. In Seoul,he went shopping and the next day he was Zorro, waist to toe, black as a crow.

His flying credentials were all there, somewhat mixed up between what they teach in modern flying schools and how to apply the ‘ivory tower’ jargon to cope with the big 747. As for raw handling of the aeroplane, all his skills were intact, only they were in bits and pieces and spread in places like an Irida Pola (Sunday Fair). They had to be streamlined, the wet market needed to be modified to a ‘Seven-Eleven’ – that was my job.

The next round we went flying to Europe, his first run to the unknown, like Gagarin in his Sputnik, young Luke flew to Rome. The flying was same as before, a bit mixed up amidst the hundreds of aero dynamical paraphernalia that spelled out from the encyclopaedic collection of books that he had to study.

That’s when I decided to change the tide.

‘Luke my friend,” I said to him in a fatherly fashion.

‘You and I are from similar fields, you from Kerala and me from Sri Lanka. These Min Drag Curves and VFEs and WAT limits and VLEs are too much for us. Just remember when you pull the stick back, the houses will become smaller and when you push the stick down, the houses will become bigger, that’s climbing and descending this monster,” I explained the simple theory of flight.

“As for landing my friend, Kudurai Madiri Pona, just ride it like a horse.”

That was it. We flew, over Europe and he flew like a Trojan, bravely battling the weather and the overcrowded skies. Every time he came in to land it was pure and simple Kudurai Madiri Pona and the big jumbo responded and touched down on the concrete as smooth as a honeymoon lover.

On the way back, we flew via Colombo, that’s my home ground. I requested the radar controller to give Luke a very short ‘four-mile’ final. They know me well here and the controller said “No problem, Captain.”

I was depicting what we did in the Old Hong Kong Airport or what we do in the Canarsi Approach in New York; both, most demanding. A ‘four-mile’ final is a challenge for anyone. I was throwing him in at the deep end and I had no doubt Luke could manage. He came in tight and right, like Hopalong Cassidy and rode the horse straight and beautiful to do a perfect landing. Gone was the Kampong kid and his ‘Irida Pola’ flying, this was Takashimaya and Robinsons rolled into one, everything was in place, nice and shining and professional to the tee.

That was our little story, Luke the ‘jockey’ and me. Sometimes in the field of training, the script needs a little changing. New acts to be introduced to suit the stage. That is the essence of teaching, different hurdles for different horses. It wasn’t for Luke to learn what I knew, more so, it was for me to know who he was and what he could cope with. That part was difficult to find in the flying training manual, and so was Kudurai Madiri Pona.

The world has gotten older and young Luke now wears four stripes and flies in command of Boeing Triple Sevens, fly-by-wire and multiple computers. I met him a few times, flew as his passenger, too, with great pride. “Captain Luke is in command,” the stewardess announced, and silently and gratefully I said, ‘Amen’.

I saw him walking down the aisle, looking for me. Same old Luke in his flat and uncombed Julius Ceaser hairstyle. He came to my seat and grinned and shook my hand and lightly lifted his trouser leg and said,

“Captain, the socks are black and it is still Kudurai Madiri Pona.

I am sure Luke will fly in command of the gigantic A380 one day. That’s a certainty. It would be the zenith for any pilot. Luke is ready, that I know. He is competent, polished and professional and will wear socks as black as midnight. It’s nice that he remembers his beginnings. That’s what flying is all about, that’s what life is all about.

Kudurai Madiri Pona

– ride it like a horse. Some flying lesson.

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