PETALING JAYA: The pollution incident in Sungai Kim Kim earlier this year has cast a spotlight on the country's waterways, but the river in Pasir Gudang is not even the dirtiest in Malaysia.
The country's most polluted river is actually Sungai Tukang Batu, which is also located in the Johor industrial town of Pasir Gudang.
Data from the Department of Environment’s (DOE) Environmental Quality Report (EQR) 2017 shows that Sungai Tukang Batu has a Water Quality Index (WQI) reading of 30 – the worst among the 477 rivers nationwide whose water quality it tracks.
Sungai Tukang Batu is the only river listed in Class 5, meaning its water is so dirty that it is not suited for use either to supply water or even for irrigation.
The WQI divides rivers into three categories: Polluted (0-50), Slightly Polluted (60-80) and Clean (81-100).
The report also separates rivers into five Classes with Class 1 being pristine and Class 5 the most polluted.
An analysis by The Star ranked the 477 rivers based on their respective WQI readings as recorded in the DoE report.
The result shows that Sungai Tukang Batu is in the top spot in terms of pollution, with Sungai Kim Kim in the 38th position.
Sungai Kim Kim has a WQI reading of 57, the same as five other rivers: Sungai Sarang Buaya and Sungai Sanglang (Johor); Sungai Pinang and Sungai Perai (both originate in Penang and flow to Kedah); as well as Sungai Bunos, which runs from Selangor to Kuala Lumpur.
Of the 477 rivers that the DOE monitors, 219 (46%) were found to be clean, 207 (43%) were slightly polluted and 51 (11%) were polluted.
Twenty-seven rivers or more than half of the 51 rivers classified as polluted are located in Johor.
Asked if the country’s highly polluted rivers could be rehabilitated, water quality expert Dr Zaki Zainuddin said that while this could be done, it would be very difficult.
“Name me one river where the attempt to improve the water quality from polluted to clean has succeeded, ” he challenged.
Malaysian authorities, he added, should instead focus on maintaining the clean rivers that the country still has, and improving the water quality of those that were only slightly polluted.
“How many clean rivers do we still have left and how to ensure that these do not get polluted five years down the road – that’s more achievable, ” said Dr Zaki.
The EQR 2017 report measured river water quality based on a total of 5,697 samples taken from 891 manual monitoring stations.
Released in December last year, this report is the most current, with the 2018 EQR expected to come out later this year.
The report also noted a slight decrease in water quality in terms of WQI for 2017 compared to the year before.
This was due to organic pollutants including wastewater from industrial, domestic and commercial activities; continuous discharge of treated and untreated sewage into the rivers; and inefficient control against improper earthworks and land clearing activities in certain areas.
Sabah has the biggest share of clean rivers in the country – of the 219 rivers nationwide classified as clean, the state is home to 53 or nearly a quarter.
Sungai Nyior in Perak meanwhile has the best water quality among all the 477 rovers monitored in the report.
The river, which was a WQI reading of 93, is the only one given a Class 1 rating.
This effectively means that the water of Sungai Nyior does not need to be treated to be used as a water supply source and can support very sensitive aquatic species.
Click here for interactive graphics and a multimedia report on the polluted rivers in Pasir Gudang and its adjacent areas.