Sorry state of Ringlet ‘Lake’

The mudslide flood in the Bertam Valley on Oct 23 is a wake up call about the critical state of the Ringlet reservoir in Cameron Highlands.

FEATURE

CAMERON HIGHLAND: Half a century ago, when the man-made lake, also known as the Ringlet Lake, came up, it used to hold enough water to power up the Sultan Abu Bakar Hydroelectric Dam.

Today, its capacity has come down drastically. Today the Ringlet reservoir is full of sand silt and rubbish

The alluvial deposits of sand, silt and rubbish that have been flowing in from the mouth of the river have filled up nearly two-thirds of the 0.5 square kilometre reservoir, seriously compromising its ability to perform its second function: flood mitigation.

Four people were killed in the recent massive floods, including one who died of a heart attack, when Bertam River overflowed following the release of water from the dam.

The floods also left 80 houses and several cars destroyed in their wake in the Bertam Valley settlement areas.

An aerial survey of the area by Bernama revealed that the waters at the reservoir and the rivers running into it are murky and looking like “teh tarik”, indicating the amount of silt and mud that they carry.

Besides, it was evident that the hill slopes around the area hit by the mud flood two weeks ago, had been aggressively leveled for development.

Ongoing farming and land clearing activities could be seen at the mouth of the river, some of it seemingly beyond control.

The aerial survey also revealed a range of machinery along the riverside, dredging out silt, sand and rubbish while smaller boats were seen removing the rubbish floating on the river surface.

Tenaga Nasional Berhad (TNB) has spent over RM180 million over he past five years, cleaning up the Ringlet reservoir and the Sultan Abu Bakar Hydroelectric Dam.

Rubbish-filled reservoir

The TNB dregs up nearly 350,000 cubic metres of silt from the reservoir every year.

However, the effort is not enough to overcome the problem as the reservoir accumulates a staggering 500,000 cubic metres of sediment every year.

Another RM300,000 is spent annually to clear nearly 200 tonnes of rubbish off the surface and the reservoir bed.

While traversing the dam and the reservoir, Bernama was told that two-thirds of the Ringlet reservoir was filled with sediment. This meant that nearly 27 metres of its depth is filled with sand, silt and rubbish.

Water flows into the reservoir from four rivers namely the Ringlet, Bertam, Habu and Tenom. The total capacity of the reservoir is around 4.6 million cubic metres of water.

However, today, not more than nine metres of its depth is filled with water.

This means that the capacity stands reduced to a mere two million cubic metres of water.

The fervent leveling of land for development and farming in the Cameron Highlands, especially along on the steep slopes and hillsides, contributed to soil erosion and exacerbated the problem of sedimentation at the Ringlet Lake.

The eroded sand and soil was being swept into the rivers and flowing into the lakes, building up sediment and making rivers and lakes shallower.

The estimated sediment amounting to around 500,000 cubic metres a year is roughly equivalent in size to nine football fields placed side-by-side and piled up six metres high.

Heavy sedimentation increases risks

TNB Cameron Highlands Power Stations General Manager Mustafa Hashim said given the shallowness of the river, a rapid rise in water level was inevitable during a downpour.

There was a risk that the rivers and dams could overflow at any time.

“A continuous downpour and heavy sedimentation from the sand, silt and rubbish would increase the risk.

“During the recent flood, the situation was made worse by the clogging of the underground tunnel water intake screen, obstructing water flow to the power generation unit,” explained Mustafa, who previously worked at the Kenyir Dam in Terengganu.

On the day of the incident, the water level in the Ringlet reservoir had risen drastically to 1.96 feet (about 0.6 metre) in the span of an hour, 13 times more than during the recent monsoon.

Water had to be discharged manually through one of the spillway gates to avert a greater disaster that could have been caused by an automatic full spillage through all four spillways.

The Cameron Highlands Hydroelectric Scheme started in 1959, combining two hydroelectric schemes into one: the Cameron Highlands scheme in Pahang and the Batang Padang scheme in Perak.

The scheme uses the “run-of-the-river” system where the water intake is through inlets along the rivers and reservoirs in the Cameron Highlands and Batang Padang.

The main rivers running along the Cameron Highlands scheme are Pla’aur, Telom, Terla, Ikan, Kodol, Kial, Bertam, Ulu Merlah, Habu, Kilat, Ulong and Ringlet.

The water from the Ringlet, Bertam, Habu and Tenom rivers fill up the Ringlet Lake through an underground tunnel 11km long. It enters the Bertam water intake to be channeled into the Sultan Yussuf power station at the 19th Mile in Cameron Highlands.

The water is then channeled into the Jor Dam before flowing 14.5km through the Menglong underground tunnel to the Sultan Idris II power station. The last station is the Odak power station at the 7th Mile, Cameron Highlands. -Bernama