Govt. decides to postpone potential Samanalawewa disaster !

By Dr Tilak Siyambalapitiya

Disasters cannot be postponed. Certainly, they cannot be prevented with 100% certainty. What governments do is to do their best to minimise the risk, based on expert advice. They err on the side of caution so that the population is satisfied that their government has done the utmost. But not in Sri Lanka!

On 24 Sept., the print media reported that Minister of Power and Energy Kanchana Wijesekera had decided to postpone repairs to the Samanalawewa leakage until 2025. No reason was given.

Samanalawewa has been in the news recently, for all the wrong reasons. In July, farmers were waiting for water to save their rice crop downstream of Samanalawewa. The power plant, which was required to produce electricity and let the water flow downstream along Walawe Ganga. Engineers were in a dilemma. They needed to operate Samanalawewa sparingly, only in the evening, 6 pm to 9 pm to keep the electricity supply to the south intact. Why was Samanalawewa so important to the south?

That’s a long story. In 1992, President Ranasinghe Premadasa cancelled the 500-megawatt Mawella (Matara) power plant because Professor Alawaththagoda Premadasa of Ruhunu University told him that the south would be a desert in 100 years if the power plant was built there. In 2013, the President cancelled the Hambantota 900-megawatt power plant saying “ane oya ithin madai”.

In 2002, the Prime Minister, after cancelling the Puttalam power plant, “ordered” the CEB to purchase two massive diesel generators, each 100 megawatt, one of which is at Embilipitiya. Faced with difficulties to serve electricity to the south, the government authorised CEB’s proposal to build a strong transmission line from Polpitiya (near Laxapana) to Hambantota. Building the line got held up in Deniyaya, with a family living in Colombo preventing it from crossing their ancestral tea estate in Deniyaya. They yielded five years later, “gifted the right of way”. Yet, we must remember: power lines do not produce electricity, as is obvious. They only transfer power. The problem of inadequate electricity production remains today, as acute as it was in the 1990s. That’s when politicians began playing ball games with power plants.

Record low water levels have allowed geologists to identify several leakage paths. This is one such “sinkhole”.

The other reason why Samanalawewa is in the news is the water leak. The public even does not remember that the embankment of the reservoir has been leaking for 30 years. Yes, 30 years!

The date was 22 October 1992. Water from Walawe ganga and Belihul Oya was released to the brand-new reservoir. Water level in reservoirs is stated in meters above sea level. The water level reached 439 metres, and there was a sudden burst.

A large leakage of water, amounting to about 7,500 litres per second, gushed down the river. It was a leak from the right-bank of the dam. The bank was expected to be water-tight, but it was not. Gradually, the leak reduced and stabilised at 2,500 litres per second and has been leaking ever since. Over the years, the leakage further reduced to about 2,200 litres per second. Yet, it is a large volume of water, escaping under the mountainous terrain, carrying with it debris, in turn indicating that further cavities are forming underneath the seemingly harmless lush green surface.

The leak amounts to about one week’s water used in an average household, gushing down the holes every second.

For the first time after 30 years, the drought in 2023 caused the Samanalawewa reservoir to be fully drawn down last August, back to its minimum water level of 425 meters. Samanalawewa spills when the water level reaches 460 meters. So, the height of water, near the dam, from the minimum to maximum, is 35 meters.

Investigations conducted in August jointly by the CEB and the University of Peradeniya, reconfirmed that leaks are from two major sources; (1) leaks along a construction access tunnel that has not been fully sealed after construction, (2) “sink holes”, which are cavities at reservoir bottom, opening pathways for water to leak downstream.

At a recent public seminar held at the Institution of Engineers, experts expressed their observations, investigations, calculations, and results. The call for immediate action was emphatic and unanimous, to take advantage of the water levels in Samanalawewa that are still very low, despite recent rains. Experts wanted water levels to recede further to investigate some leakage paths that are still not visible, and for immediate rectification work to be done. Rectification will require soil, mud and concrete, depending on the final decision of geologists and engineers.

The mini-hydro saga

There are two mini-hydro power plants on the Walawe River. They were built to use water downstream of the Samanalawewa dam; water which is not used to produce electricity from the CEB’s Samanalawewa power plant. Sri Lanka’s mini-hydropower plants (all privately-owned) had an average capacity factor of 43% in 2021. Apologies for the jargon — the capacity factor indicates the equivalent time a power plant produces electricity over a year, given the variation of river flow. The prices of electricity produced by the private mini-hydros that signed up in the 2013-2016 period were based on a capacity factor of 42%.

However, the two mini-hydros downstream of Samanalawewa have reported a capacity factor of 55%, ably supported by the godsend water “leaking” from the reservoir. Therefore, the two mini-hydros, both threatened of a complete washout in case of a disaster, who may well have recovered their investment at least twice over, should be the most interested in making sure that the reservoir is safe as it could be. Although some newspaper reports wrongly indicated that the mini-hydro owners are “against” the leak being plugged, they must be pushing the government to plug the leak and make their investments secure.

The Institution of Engineers held yet another seminar last week, featuring Australia’s key dam safety expert, a Sri Lankan, to drive home the point that Samanalawewa needs to be made safer. Other dams, too, have to be examined, and most importantly, all dams must have an evacuation plan, in case the unthinkable happens.

Eight officials jailed after dam burst

Not in Sri Lanka, but in Libya last week. Not only the present officials but the former officials, too, were jailed. Libya does not even have a unified functioning government, but Sri Lanka has a government.

The Sri Lanka government, too, acted when geologists and engineers were pleading with it two weeks ago to go ahead with Samanalawewa investigations and carry out repairs. It would require water levels to be reduced further, and a quick set of actions in succession to make the reservoir safe.

In its customary style, the government appointed a committee to prepare a report on the safety of all dams, with no special emphasis on Samanalawewa. The Ministry of Power and Energy, which is in charge of Samanalawewa, announced the repairs will be done in 2025. Until then?