The Very Scary Recent Digana Quakes

The four quakes reported in the vicinity of the Victoria Dam in Digana naturally alarmed us Sri Lankans. I was more than concerned having spent so many wonderful holidays in the circuit bungalow in an enclave of a township constructed for the engineers of Balfour Beatty Plc, the British multinational infrastructure group based in the United Kingdom which was entrusted with the construction of this British Government funded project of the Accelerated Mahaweli Development Programme. The swimming pool was an attraction whether to be in it or outside, seated on its apron having ordered food from the restaurant. But latterly standards dropped and our holidays there ended. We went to other nearby holiday resorts, however.

Incidentally, Balfour Beatty and its engineers received awards for the design of this unique double concave cement dam. You will remember the astounding sight of the water rising high on the other side of the dam to cascade down and be channeled to other reservoirs and conduits to irrigate newly opened land. The button to commission the dam was pressed by Margaret Thatcher, then PM of Britain, with youthful Gamini Dissanayake and his wife beside her; also the promoter of the Diversion Scheme to five years from its proposed 30 years – President J R Jayewardene. This was on April 12, 1985, with work having started on this dam on August 14, 1978.

I well remember stopping in the Digana area on a family trip and being allowed to visit the dam site while preliminary work had just begun. White marks were seen up high on the hills surrounding the stream far below. Imagine my surprise when told the reservoir waters would rise to the white marks. Stunning! Just as it was when going past along the Kundasale and Haragama roads seeing only the crowns of coconut trees above the collected water. For a while Gamini Dissanayake’s family were neighbours to us on Sangarajah Mavata, Kandy, hence also the keen personal interest in the Accelerated Mahaveli Scheme. The new township of Digana was admired and oft traversed, being designed by Ulrich Plesner who was employed in the Mahaweli Scheme to plan and have built new townships all over reclaimed and newly irrigated land.

Most scary was the imagined disaster if the Victoria Dam was affected and succumbed to earth tremors. The output of water is stunning enough when the sluices are opened. What would it be if the dam was damaged?

An experienced geologist’s reckoning

I phoned a retired university academic living in Kandy about the danger to the dam with the recent quakes. He consulted a geologist nephew who had been involved with the construction of the Victoria, Randenigala, Samanalawewa and other reservoirs. He said the dam had been built extremely well on almost invincible scientific principles and that a quake of only seven and above on the Richter scale would cause damage to the dam. The recent quakes were around 2.5. His assurances were merciful. The geologist added that the geologists from University of Peradeniya who had been consulted had given correct prognoses and advice. But of course quarrying in the vicinity of the dam was a positive danger and had to be stopped immediately. He reiterated that expertise was perfect in the construction of the dam with the best of Balfour Beatty coming here. At that time, he added, seismic activity was not considered when constructing a dam, unlike now when Japan first sets out on such testing. Plates below the Digana area do move.

Another assurance given was that even if the Victoria Dam was damaged, Randenigala and other reservoirs which this resevoir feeds would not be damaged.

Further input

An article I read gave more general information. Titled Can Humans Start an Earthquake? Reservoir induced seismicity – making the Earth move was by Julia Layton. She writes:

“Until recently, the most powerful attributed to dam activity happened in western India in 1967. Three years after builders completed the Koyna Dam, a 6.5-magnitude earthquake hit the area, killing 180 people. The phenomenon of dam-triggered earthquakes is known as reservoir-induced seismicity. It’s not well-understood, but what happens is this:

When a dam is built and the reservoir filled with , the amount of pressure exerted on the earth in that area changes dramatically. When the water level of a reservoir is raised, pressure on the underlying ground increases; when level is lowered, pressure decreases. This fluctuation can stress the delicate balance between tectonic plates beneath the surface, possibly causing them to shift.

“Another factor is the water itself. When the water pressure increases, more of it is forced into the ground, filling cracks and crevices. All of this water pressure can expand those cracks and even create new, tiny ones in the rock, causing greater instability below ground.

“One thing we do know, however, is that a dam cannot cause an earthquake all by itself. The risk factors, specifically unstable fault lines, have to be there already, which is why it’s so dangerous to build a dam over a known fault.

“And it’s why so many scientists are warning of terrible results of China’s , which is built over the Jiuwanxi and the Zigui-Badong fault lines. Some say it’s only a matter of time before the dam triggers a major earthquake, possibly like the one in Sichuan Province in 2008.”

External activity must cease

In the Victoria Dam case we are considering the damage to the dam by quakes in the earth and not vice versa. However, it is imperative all mining, deep digging and all that must stop immediately in the entirety of the area. The earth over there is limestone deep down and people mine it with, as usual, no concern at all for consequences and hazards to the atmosphere and ecosystems. Immense caution is needed due to the quarrying being in the immediate vicinity of the massive dam, with strong explosive devices used. Money seems to be all that matters; proven over and over.

In this country, powers that be, whether political or administrative, are known for closing the stable door after the horse has bolted. Let our government shut the stable door before the stallions of mining and deforestation continue their destruction. They have already escaped and are causing irreparable damage. STOP harmful mining of limestone, sand, granite, especially using strong dynamite; deforestation and draining swamps and mangroves. Damage has already been done by the rapacious; let it be stemmed even at this late stage.

Note:

Julia Layton has a B.A. in English Literature from Duke University and a Master of Fine Arts from the University of Miami. She is a university lecturer and also a freelance writer/ editor; contributing to web sites – HowStuffWorks, The Learning Channel, and Forbes.