TNB has conceded that siltation from “massive land clearing and farming activities upstream” contributed to the rapid increase of the Ringlet Lake water level and the sudden discharge of the overflow.
The “accumulation of siltation and sediment had reduced the reservoir’s holding water capacity”, said TNB in a statement.
I am not sure TNB can wash its hands so easily, though.
No specific mention of any logging activities? If you look at the map above, you can see lighter green patches in the Habu area/Bertam watershed, which suggests this could be secondary forest (in contrast to the darker green primary forest). Was the primary forest logged?
Who is responsible for supervising the integrity of the catchment areas and preventing such massive land-clearing?
If you are going to manage a reservoir or dam, surely you bear responsibility for protecting the water catchment areas from being degraded or compromised. You also have a responsibility to ensure that there is no risk to human life downstream and to prevent any encroachment in the path of emergency water overflows.
This reminds me about the water catchment areas in those dams they are building in Sarawak. Some time ago, Aliran had published an article pointing out that the establishment of plantations in the 1.5m ha water catchment area for the Bakun Dam could threaten the viability of the dam. There are also concerns about plantations upstream of the Murum Dam.
TNB press release
WATER RELEASE FROM SULTAN ABU BAKAR DAM WAS INEVITABLE
The rapid increase of the Ringlet Lake water level within a short period of time late Tuesday and early Wednesday is an exceptional situation for the Ringlet Reservoir, said TNB President/CEO, Datuk Seri Ir. Azman Mohd.
The unusually intense downpours on October 22 and 23 had brought huge volume of water to Ringlet Lake together with solid wastes, debris and siltation from the massive land clearing and farming activities upstream.
The rubbish clogged up the Bertam Water Intake, an outlet where water from the Ringlet Reservoir normally flows before entering the Bertam tunnel to an underground power generation units. Such accumulation of siltation and sediment had reduced the reservoir’s holding water capacity.
As a result, for the first time in the history of the 50 year old reservoir, water level surged at a rate of 1.5 ft per hour, which is three times more than the normal monsoon rain condition.
Surplus water had to be discharged in stages from Sultan Abu Bakar dam to avert the dam’s automatic full spillage through all four spillway gates that would have caused greater destruction to the occupants of Bertam Valley.
By design, a spillway gate is a dam protective structure used to provide the controlled release of water flow from a dam into a downstream river. Downstream area should be clear of people and structures.
Azman said given the challenge of these external factors, which were beyond TNB’s control, it was impossible to give advance notice to immediately evacuate the water release pathway other than what had already been done in the circumstances.
“While we could and should be continuously improving our Standard Operating Procedures (SOPs), given the circumstances we seriously doubt whether any SOP can be fully effective in averting such a disaster,” said Ir. Azman.
He also said that no one should have lived in the path of the dam’s water release and the weather elements together with the development activities are introducing greater unpredictability to the situation.
“We are continuously monitoring the situation and we experienced a rate of rise of water level of 1.2 ft per hour from 4 PM to 6 PM yesterday. A sudden blockage of the power station’s intake can trigger another catastrophe.
S.A. 2013/10/99 (HQ)
“The people living in the area are still not out of the woods yet as development activities that have caused Bertam reservoir to lose its water holding capacity continue to gain momentum.
“We don’t think anybody can guarantee the safety of the people at the site given the present conditions. Thus, they should be kept out of harm’s way and vacate the area,” he added.
28 October 2013