Kelani Ganga at a crossroads: Suranjan Karunaratne warns of an unfolding crisis

From the misty montane forests around Adam's Peak, the Kelani Ganga tumbles down rocky headwaters, gathering tributaries before rolling past rubber estates, tea plantations, shanty towns and finally Sri Lanka's bustling commercial capital. For centuries this 145-kilometre river has been the country's lifeline, supplying water, fish, fertile soils and cultural meaning. Today it sustains more than six million people in the Colombo District alone.

- BY IFHAM NIZAM

Biodiversity of the Kelani Ganga

But the river is in trouble.

Speaking to The Sunday Island, Environmental Scientist Suranjan Karunaratne of the Nature Exploration and Education Team, said; “The Kelani River has become one of the most heavily impacted river basins in Sri Lanka,” and Karunaratne has spent years documenting the basin’s ecology.

Karunaratne is not speaking off the cuff. He is coauthor of a landmark review on the Kelani River published in Water (2020) with Thilina Surasinghe, Ravindra Kariyawasam and others — one of the few peer-reviewed papers to pull together the basin’s biodiversity and threats. “Our research combined published literature with our own field observations to give the most comprehensive picture yet of the river’s condition,” he explains. “What we found was alarming.”

According to Karunaratne’s research team, only about 10 percent of the Kelani’s catchment remains forested. The once-continuous riparian vegetation — towering trees that shaded streams and filtered runoff — has been reduced to narrow strips of grass and scrub along Colombo’s outskirts.

“Riparian forests act as the river’s kidneys,” Karunaratne explains. “They filter sediments and nutrients, stabilise banks and regulate water temperature. When we clear them, we disable the river’s self-cleaning system.”

His study, based on Sri Lanka Survey Department data and field checks, documents how rubber and tea plantations, in the mid and upper basins, have crept into floodplains and headwaters, while urban expansion, in the lower basin, has displaced wetlands that once soaked up floods and recharged groundwater. Today, less than one percent of the basin remains wetland.