KUALA LUMPUR: Sungai Pahang is in danger of drying up soon, and the weather is not totally at fault.
Water quality specialist Dr Zaki Zainudin told the New Straits Times that it was important not to attribute the troubles facing Sungai Pahang, the longest river in Peninsular Malaysia at 459km, to a single factor. Other factors at play include conversion of forests into oil palm plantations, agriculture, tin and gold mining, and logging.
Development and human activities in Sungai Pahang catchment areas go back more than 20 years, but, Zaki said, the magnitude was smaller then, making the impact not as obvious. He said as more development took place, the impact gradually became more pronounced.
“Conversion of forests into oil palm plantations, and logging also disrupt the hydrological balance, as forests help retain water. Wildlife habitats are also destroyed. These activities affect water quantity (flow and/or depth), water quality and aquatic ecology. There are socio-economic ramifications, too.
“Erosion of topsoil happens as there is no more underlying growth and roots to hold the soil together. No more vegetation to help filter run-off.”
Zaki said when it rained, vast amounts of solids would be washed into the river from oil palm plantations and logged areas, causing once clear water to turn brownish, like milky tea. He said these solids — called suspended solids — did not remain suspended in the water, but settle to the bottom of the river, making some part of the river shallow. Solids that have settled on the river floor are called sediment.
Besides suspended solids, fertiliser residue that contain ammonia, nitrate and phosphorous, also end up in the river. He said the increase of suspended solids also affected aquatic life, for example, causing fish gills to become clogged.
Zaki said coupled with higher temperature, mainly caused by El Nino, more pollutants become more concentrated because of lower dilution and decreasing water depth.
“The El Nino phenomenon has certainly magnified the flow reduction. Long, dry periods deprive the catchment areas of rainwater recharge.”
Zaki said this led to the aquatic ecosystem becoming stressed and fish dying. He said sediment also wiped out fish breeding grounds, when rocks and pebbles, where fish lay eggs before insemination, become covered with muck.
“All these human activities take place upstream of Sungai Pahang,” said Zaki.
Checks by the NST last week found this to be true. Zaki said two major hydroelectric dams were also being built on two major tributaries of Sungai Pahang.
He said there would be no problems if enough water was released from these dams. However, Zaki said, the worry was if little water was released — such as when the dams’ reservoirs were being filled. He said other rivers in the country were also at risk.
“Malaysia is the second largest palm oil producer in the world. This translates to many of our watersheds being converted to oil palm plantations, be it in Peninsular Malaysia, Sabah or Sarawak.”
Reports of Sungai Golok in Kelantan drying up to knee level have also caused concern. Based on satellite imagery, Zaki said, parts of the river catchment area had been developed for agriculture.
Besides El Nino as the driving fac tor in bringing the waters of the river at the Malaysia-Thai border to knee-level, he said development definitely had some effect.
Another expert, who did not wish to be named, said rivers in Sabah and Sarawak were in an even worse state.
He said because of the vastness of the forests there and the remote location of the rivers, it was difficult to carry out enforcement. The impact of sediment on Sungai Rajang, the longest river in Malaysia at 563km, was worse than in Sungai Pahang.
He called it “the milk tea with extra milk” river. “You can see it, all the way from where it starts up to its confluence; it is brown like milk tea. Thank goodness it is big and has a lot more smaller rivers to recharge it,” he told the NST.
The professor said Sungai Kinabatangan in Sabah and Sungai Kahang in Johor were also suffering from the effects of logging. Zaki said it was okay to use natural resources for economic gain, but over exploitation had led to the dire state of affairs.
“What is transpiring now are cues for what the future might hold. Are we going to sit back and pretend everything is still okay? Blame it solely on factors beyond our control, such as El Nino? What about factors within our control? What are we going to do about that?”
It was reported earlier this month that Pahang Menteri Besar Datuk Seri Adnan Yaakob had ordered an investigation into allegations that the main cause of Sungai Pahang becoming shallow was excessive logging in Hulu Tembeling.
“Indeed, one of the reasons for Sungai Pahang going dry is because of the clearing of forest for agriculture, logging and, as we know, there is the construction of the Tekai and Jelai hydrodams going on in the region.
“Nevertheless, we will ask the technical department to give a full and accurate report,” he said.