Sri Lanka’s major drinking water sources—including the Mahaweli, Kelani, and Badulu rivers—have been found to be significantly polluted, raising serious health concerns.
A 2023 study by the University of Peradeniya confirmed bacterial contamination in both surface and treated water along the Mahaweli River, especially between Kotmale and Victoria reservoirs.
Testing showed that bacterial levels in treated water from 10 out of 14 water treatment plants exceeded the maximum safe limits set by the US EPA.
Contamination varied seasonally, increasing during the wet season due to runoff and drains carrying septic waste.
Although most treatment plants achieved more than 77.9% bacterial reduction, the presence of high bacterial loads indicated gaps in disinfection processes.
The study recommended improvements in water treatment and disinfection, especially during the rainy season, to ensure safe drinking water.
In the Kelani River Basin, another study found widespread presence of harmful bacteria including E. coli, Salmonella, Shigella, and Campylobacter in both surface and groundwater samples.
Most water samples from the Kelani River Basin exceeded Sri Lankan standards for safe drinking water, posing a risk of gastrointestinal illnesses.
Researchers identified 23 human pathogenic Salmonella serovars, with Salmonella enterica serovar Kentucky being the most common.
Experts warn that consuming untreated water from these rivers can lead to serious health issues, and urgent action is needed to improve water safety across the country.
