River Care Safeguards Water Supply During Dry Season

Although the country has experienced water crises due to prolonged droughts that affected raw water storage in dams, communities – especially in the Klang Valley, which often faces raw water shortages – have still had access to this vital resource.

In Malaysia, rivers serve as the primary sources of raw water for domestic, agricultural and industrial use. Hence, protecting these rivers is crucial to ensure a continuous and safe water supply for the population.

The Department of Irrigation and Drainage (DID) recently organised an expedition (‘Ekspedisi Sumber Air’ or EKSAN 2025) to Pahang to raise awareness on the importance of water conservation.

The expedition, from June 30 to July 2, saw the participation of about 100 representatives from government agencies and non-governmental organisations, as well as researchers and media practitioners, who were taken to several key locations within the Pahang river basin, which is the main water source for the state.

One of the places they stopped at was Kelau dam located in Felda Kelau, Sungai Kelau, about five kilometres upstream of Sungai Bilut in Bentong.

According to water services provider Air Selangor vice president I Jaffry Rabu, the Kelau Dam is one of the components of the Pahang-Selangor Raw Water Transfer Project implemented by the federal government. With a storage capacity of 147.1 million cubic metres of water, the dam is intended to meet the water needs of the Klang Valley.

The dam is capable of supplying 1,890 million litres of raw water daily to the Langat 2 Water Treatment Plant (WTP) in Hulu Langat, Selangor, via a 44.6-kilometre water tunnel that cuts across the Titiwangsa Range. It is the longest water tunnel in Southeast Asia. This tunnel also facilitates water transfer from Sungai Semantan (in Pahang) via the Semantan intake to the Langat 2 WTP.

“When the Langat 2 WTP is operational, the Kelau Dam can supply approximately 20 percent of Selangor’s water needs, with the remainder coming from Selangor’s own dams,” explained Jaffry.

In addition to the Kelau Dam, Air Selangor owns other dams: Sungai Selangor and Sungai Tinggi Dams (Hulu Selangor), Tasik Subang Dam (Petaling), Sungai Langat and Semenyih Dams (Hulu Langat), Labu Off-River Storage Pond (Sepang) and the Klang Gates and Batu Dams (Gombak).

According to recent media reports quoting Pengurusan Aset Air Bhd, the first phase of the Langat 2 WTP project – which costs approximately RM4.2 billion and is funded by the federal government – has been fully completed and is expected to begin operations in August. Langat 2 WTP is expected to resolve water shortage issues in Selangor.

 

Meanwhile, in Pahang, the main source of raw water supply is the 459-kilometre-long Sungai Pahang, Peninsular Malaysia’s longest river, which originates in the Jerantut district in western Pahang and flows through several districts before ending in the South China Sea to the east.

The expedition participants also visited Taman Negara, setting off by boat from the Kuala Tahan jetty and cruising along Sungai Tahan and Sungai Tembeling, which are part of the Pahang river basin.

The participants stopped at various places along Sungai Tembeling, including an Orang Asli village in Jeram Dedari, home to about 30 people of the Batek tribe; Lata Berkoh, a natural waterfall surrounded by dense rainforest; and the Kelah Fish Sanctuary, established by the Department of Wildlife and National Parks as a conservation zone for the kelah fish species.

Against the backdrop of the pristine waters flowing from the Lata Berkoh waterfall into major rivers like Sungai Tahan and Sungai Tembeling, the participants received a briefing and demonstration on water sampling by a team from the Faculty of Ocean Engineering and Informatics, Universiti Malaysia Terengganu, led by senior lecturer Dr Mohd Sofiyan Sulaiman.

Mohd Sofiyan explained that water quality is determined through parameters such as pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (AN) and suspended solids (SS).

“The measurements are calculated and used to determine the overall water quality index (WQI), which is then used to classify rivers as Clean (81-100 percent), Moderately Polluted (60-80 percent), or Polluted (0-59  percent).

“The decline in WQI status for rivers not only affects aquatic life but also limits the usability of water resources for human purposes, including daily activities,” he said.

He said water quality monitoring is usually conducted by DID and the Department of Environment through composite sampling – samples taken from several locations along the river at depths of at least 0.5 metres from the surface.

“pH readings are usually taken on-site using portable meters for immediate results as water temperature changes can affect pH values in a short time,” he added.

 

Mohd Sofiyan also explained there is a distinction between the terms “water source” and “water supply”, pointing out that a water source refers to raw water available in rivers, lakes or dams, whereas water supply refers to water that has been treated at WTPs.

He said as of last year, a total of 340 WTPs have been built across the country, with 80 percent of their raw water sources comprising rivers.

“If we look at the current plant capacity, there’s a term called the reserve margin, which refers to the difference between supply and demand. For example, if the water demand is 100 million litres and our plant can produce 120 million litres, we have a 20 percent surplus margin.

“According to the latest data, we have a relatively healthy reserve margin of about 15 percent, with three states showing higher margins – Penang (30 percent), Perak (26 percent) and Terengganu (25 percent).

“When a WTP has a high reserve margin, it means there’s excess water that can be used in times of emergency, especially during dry seasons,” he said, adding that the reserve margin usually depends on the size of the WTP and the current water demand in the state.

He added that unpredictable climate change is putting pressure on the country’s raw water sources as catchment areas are receiving less rainfall. Prolonged dry conditions may result in no rainfall, and in some cases, heavy rain may fall outside catchment areas or only briefly within the areas concerned.

Mohd Sofiyan also said there is a need for an in-depth study on the Water Stress Index in line with climate change.

“For example, looking ahead to 2050, we must map the availability of water resources against projected demand based on population growth,” he said.

He added that by using this index, authorities can identify whether the country is under no stress or facing critical stress as rainfall distribution directly affects the availability of water resources in Malaysia.

 

Meanwhile, DID deputy director-general (business sector) Mohd Azmin Hussin said to ensure water sufficiency, especially during droughts, the department has developed the National Water Balance Management System (NAWABS) to improve water management efficiency.

NAWABS is a comprehensive integrated water resource management instrument implemented at the river basin level. It is designed to monitor and forecast rainfall, water levels and river flow rates, including in dams and intake points, and to provide continuous data on water resource availability.

Through NAWABS, DID is able to forecast drought conditions up to two months in advance and issue drought warnings 14 days ahead. This helps provide up-to-date information on water availability in a given basin area, especially regarding river levels, dam storage and available capacity for irrigation and domestic water supply, Mohd Azmin said.

“The development of NAWABS is being carried out in phases. Phase one was approved by the Economic Planning Unit (now known as the Ministry of Economy) in 2017 and successfully covered seven river basins.

“We are now implementing phase two, which was approved in 2018, involving 12 more river basins, including the Pahang river basin,” he said.

He emphasised that water is not a static resource, but part of the Earth’s complex life ecosystem and therefore exposed to various risks.

“Disruptions to the water cycle, river pollution and climate change all contribute to water resource management crises, which can ultimately affect a country's political and economic stability.

“Access to clean water is the foundation of health, survival and peace. Therefore, today’s generation must be educated on the intrinsic value of water and the interconnectedness of communities by instilling in them a sense of empathy and responsibility for water resources to ensure their sustainability,” he added.