Malaysia: Sediment reduces dam’s capacity

LOSHANA K SHAGAR The Star 3 Oct 16;

CAMERON HIGHLANDS: Sedi­ment that covers the equivalent of 80 football fields rising two storeys high sits at the bottom of the Ringlet reservoir here.

This has reduced the dam’s water capa­city to less than half of its original amount.

An estimated four million cubic metres of sediment clogs the man-made Ringlet Lake despite extensive dredging efforts by Tenaga Nasional Bhd (TNB).

TNB generation division (asset operations) senior manager Roslan Abd Rahman told reporters during a site visit to the Sultan Abu Bakar Hydroelectric Dam recently that the reservoir could hold only 2.7 million cubic metres of water, far less than half its actual capacity.

Four water sources flow into the dam, namely the Ringlet Lake and the Bertam, Habu and Tenom rivers. Bertam Valley is next to the dam.

The site visit revealed that the water in the dam was murky due to sedimentation.

Residents are concerned that there could be another mudslide if there are heavy downpours over the next three months.

In October 2013, excess water that flowed into the reservoir had to be released, causing massive floods and four deaths.

“Once the water level at the Sultan Abu Bakar dam hits 3,513 feet, the dam gates will automatically open, but the danger is that releasing so much water at once will endanger valley residents.

“This is why we have lowered the operating level to 3,500 feet during the monsoon season, so we have more response time to manage the water storage,” said Roslan.

TNB spent over RM180mil between 2008 and 2013 to clean up the Ringlet reservoir and the Sultan Abu Bakar Hydroelectric Dam, dredging up nearly 350,000 cubic metres of silt every year.

However, the reservoir has since 2014 been accumulating a staggering 500,000 cubic metres of silt per year, forcing TNB to increase its dredging activities to clear 750,000 cubic metres a year.

“Also, some two tonnes of solid wastes every week is collected from the reservoir. This amount increases during a heavy downpour.

“We are doing all we can to clear the sediment and rubbish, but these efforts are not going to be sustainable in the long run if the sediment and rubbish keep increasing,” said Roslan.

About RM80mil was spent in 2013 and 2014 just to remove rubbish from the water sources.

Even the recently completed Susu Dam and the Ulu Jelai Hydroelectric power project sites nearby were showing signs of sedimentation, despite being very new, Roslan said.

“As long as people’s attitude towards disposal of rubbish and land clearing does not change, our actions will not have much effect in the long run,” he said.

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