THE Sarawak River is a lifeblood of Kuching city and its surrounding areas, serving not only as a useful mode of transportation but also as a life-sustaining source of water for the residents.

But its resources are gradually depleting and without proper management, there may come a day when scarcity of water will pose a problem for the state capital.

To prevent this, plans to ensure water security have been drawn out and a right step in this direction is the construction of the Bengoh Dam scheduled to become operational by 2010, barring any delay.

“The dam is built to ensure that adequate raw water — in conjunction with the balance of the Sungai Sarawak Kiri catchment — is supplied to the Kuching Water Board’s Batu Kitang water treatment plant in times of low rainfall (in the catchment area) to meet the water requirements of Kuching and its surrounding areas such as Samarahan, Asajaya, Sadong Jaya, Tasik Biru-Lundu-Sematan, Tapah-Beratok-Siburan and Serian up to the year 2030,” explained project director, Roland Ling of KTA Sarawak.

He pointed out that people tend to take the availability of water for granted and if this trend continued and there were no conservation efforts, the people might soon be facing a depletion in water resources.

According to him, the supply of water from the Sarawak River was sufficient for the population of Kuching and its surrounding areas some 30 to 100 years ago.

“However, the population of Kuching has grown by leaps and bounds, and not many people realise that it has actually reached a stage where by 2010, the current volume of water supply from the Batu Kitang area will soon outstretch its optimum stable supply capacity,” he cautioned.

Construction of the Bengoh Dam began last year on Sungai Bengoh which adjoins Sungai Semadang to form the upstream end of Sungai Sarawak Kiri.

The site is about 40km south of Kuching and about 2km from Kampung Bengoh accessible from Kuching by bitumen road.

On the choice of the location, Ling said the terrain provided a significant natural water basin, especially when Sungai Bengoh was dammed up.

“The site provides a significant reservoir area and plus a sufficient volume upstream for a relatively small dam. There are no low points on the reservoir boundary to limit dam height or require secondary saddle dams.”

Ting said the dam is located in a straight, narrow and steep stretch of the Sungai Bengoh valley and once completed in two years, the river catchment raw water resource is capable of meeting the water demand projection for Kuching City and its surrounding areas up to 2030.

Beyond that, additional water supply sources will have to be found to meet the ever increasing demand.

“There is also reasonably sound rock in the riverbed and valley forming a solid foundation for a Roller Compacted Concrete (RCC) dam,” he added.

When completed, the 63.2m high Bengoh Dam will be the second RCC dam in Malaysia after the Kinta Dam near Ipoh, Perak.

According to Ling, it will also comes complete with reinforced concrete dam galleries, draw-off tower, spillway bridge and crest, outlet weir, valve chamber, dam drainage and grouting, river diversion, piping works, mechanical and electrical works, dam operation office and other associated facilities.

He revealed the environmental management and protection measures such as construction of silt traps, soil erosion and scour protection, and vegetation had also been carried out.

“The main objective is to secure sufficient water supply for Kuching city and its surrounding areas. With a storage reservoir area of 10.2 sq km at full supply level, this dam has a reservoir capacity with a storage volume of 144.1Mm3, thereby providing enough supply of water to last for two months of zero rain from the year 2030 onwards.”

Ling also said the treated and raw water demand up to the year 2030 is projected to be 1,945 million litres per day (Mld) and 2,047Mld respectively.

He disclosed that the projected water supply shortages were confirmed by consultants engaged by the state government to study the critical impact of water availability today in comparison to the projected population growth and treated water demand up to 2030.

With the main existing source of raw water supply for Kuching and its surrounding areas running from Sungai Sarawak Kiri and based on research and historical records, he noted that the assessed run-off safe yield from the river at the Batu Kitang water treatment plant — with the weir in place for the one in 50 ARI seven-day flow of 600Mld — would cater for needs of the population in Kuching up to 2010 only.

“We are very lucky so far this year. We have not experienced any prolonged dry spell. I recall that four years ago, on July 2, 2004, after a month of dry spell, the water level at the Batu Kitang raw water intake facility dropped to -0.6 m LSD. With an abstraction rate of 300 Mld the water level dropped at 0.1m per day,” he said.

“During that occasion, there was saline intrusion into the raw water intake facility, resulting in a change in water quality, among others. Another 10 days of drought would have resulted in very serious water shortage problem but fortunately rain came the very next day (July 3).”

According to Ling, the current raw water demand for Kuching and its surrounding areas is estimated at 545Mld whereas the Batu Kitang water intake facility is only capable of a supply of 600Mld.

“This demand is projected to increase to 635Mld within the next three years, with further projection of raw water demand rising to 2,047Mld by the year 2030,” he said, adding that it was essential for the raw water supply source to be augmented by the Bengoh Dam by year 2010 to meet the projected needs.

“Water is a precious resource, and this is never more apparent than in time of drought. Further plans to continue conserving and securing water after the year 2030 are on-going as well.”

The proposed storage reservoir area behind the dam is also expected to promote tourism-based activities and provide impetus to the two rural development programmes already initiated in the area by the government.