Suranjan Karunaratne in The Island, 2 October 2025, with this title “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.
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 co-author 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.”
Riparian Forests: The River’s Kidneys Under Siege
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.
Pollution Hotspots: A Toxic Cocktail
Karunaratne and his co-authors compiled decades of water-quality data showing the lower basin now routinely fails to meet drinking-water standards. Point-source pollution is staggering: more than 6,000 factories release thermal effluents, oils, heavy metals and synthetic compounds. Biological oxygen demand in the lower reaches has been measured at 17 mg L — far exceeding safe thresholds — while pH has dropped to 5.3.
Non-point pollution is just as severe. Storm-water canals flush urban waste into the Kelani during monsoons, while fertilisers from tea, rubber and paddy fields spike nitrogen and phosphate levels, fuelling algal blooms. Ammonia in the coastal reaches already averages at the permissible limit.
Dams, Diversions and Dredging
Hydrological change compounds these chemical assaults. Karunaratne’s paper lists five major hydropower reservoirs and 32 mini-hydropower plants fragmenting the river, with another large plant under construction. “Impoundments change flow regimes, water chemistry and the physical habitat of fish,” he notes. “In some tributaries, 60 percent of their length has become dead or low-flow reaches.”
The consequences ripple through the food chain. Fish adapted to oxygen-rich rapids cannot survive these altered conditions. Migratory cyprinids find their routes blocked. Even diadromous gobies whose larvae migrate to the sea depend on unimpeded flow and intact estuarine habitats.
Karunaratne and his colleagues also documented widespread illicit water extraction and sand and gem mining, which reshape the channel and lower flows to the point that seawater now intrudes 15 km inland during droughts.
Biodiversity on the Brink
The team’s survey recorded 60 freshwater fish species in the Kelani basin — more than half of Sri Lanka’s endemic freshwater fish — along with critically endangered crabs, dragonflies and amphibians. Yet 22 fish species are nationally threatened.
Micro-endemics, such as the Bandula Barb (Pethia bandula), survive in a single tributary, while the Asoka Barb (Systomus asoka) is confined to a few foothill streams. Filling wetlands threatens swamp eels in the coastal zone. “Even occasional fish kills have been reported in lower reaches due to industrial and domestic waste discharge,” Karunaratne says.
Adding to the pressure is an invasion of alien species — tilapias, vermiculated sailfin catfish, clown featherbacks and even red-eared slider turtles. Karunaratne’s article lists more than two dozen exotics established in the basin. These species compete with native fish, prey on smaller species or eggs, and in some cases physically alter habitats.
Weak Policy, Weaker Enforcement
Sri Lanka has more than 20 governmental agencies and over 50 statutes regulating aquatic resources, yet coordination is poor and enforcement patchy. Karunaratne’s study devotes an entire section to policy gaps, noting that mandatory streamside reservations are often ignored and environmental impact assessments rarely translate into mitigatory action.
“Without science-based policymaking and inter-agency cooperation, even the best laws are just words on paper,” he laments.
A Blueprint for Recovery
Despite the grim outlook, Karunaratne believes the Kelani can still be saved if action is swift and strategic. His research paper closes with a suite of recommendations:
Reforest riparian buffers:
* Restore meanders and reconnect floodplains.
* Establish freshwater protected areas.
* Control invasive species and avoid planting alien flora.
* Evaluate the river’s ecosystem services in monetary terms to persuade policymakers.
* Invest in research and monitoring, including permanent survey stations and studies of endemic fish breeding biology.
“Kelani Ganga is not just a water source; it’s a living system that underpins Colombo’s health, economy and cultural identity,” Karunaratne says. “If we don’t act now, we risk ecological collapse and public-health crises.”
A River, a Mirror
In many ways, the Kelani reflects Sri Lanka’s development dilemma: the tension between economic growth and environmental stewardship. Its challenges echo across other tropical riverscapes in South and Southeast Asia.
But Karunaratne sees an opportunity. “If we can turn the Kelani into a model of integrated river-basin management, we can inspire conservation of other rivers,” he says. “It will take stakeholder partnerships, participatory management and a willingness to treat the river not as a drain, but as an asset.”
As the Kelani flows past tea-green hillsides and shanty-lined banks toward the sea, it carries both a warning and a hope. The warning is stark: unchecked degradation will lead to ecological collapse. The hope lies in the science and passion of people like Suranjan Karunaratne — and in society’s capacity to heed their call.
Our judiciary takes action against those who harass elephants and other animals that cannot talk. The other part of the ecosystem, the trees, forests, and rivers are silently suffereing