Preliminary study by varsity department points to dip in oxygen level

The mass mortality of fish reported from the stretch of the Karamana, near the Thiruvallam and Pallathukadavu ghats last week, could have been caused by the unusual rise in water temperature, reduction in flow and a surge in the concentration of sewage pollution.

A preliminary study conducted by the Department of Aquatic Biology and Fisheries, University of Kerala, says the mass fish kill was due to an abrupt dip in the dissolved oxygen in water. Head of the Department A. Biju Kumar says the rise in temperature and reduction in water flow coincided with the summer. The heavy sewage pollution from the Parvathy Puthanar canal could have aggravated the conditions, killing fish in large numbers, he says.

Hundreds of dead fish, including pearl spot, barbs, and a few marine species that fond their way inland through the estuary were found dead in the water, triggering public concern. Despite repeated assurances from the State government, the heavy pollution of the downstream stretches of the Karamana river continues unabated, posing a grave environmental and health hazard for the residents at Thiruvallam and on the Edayar island. Four weeks ago, 20 children who were attending a swimming camp at Thiruvallam contracted leptospirosis, prompting health officials to sound the alarm.

Officials say that cleaning up of the heavily polluted Parvathy Puthanar canal is crucial to the restoration of the river. But the construction of a sewage treatment plant at Muttathara has been dragging on for years.

The Karamana runs through the city, joins the Killi at Pallathukadavu (upstream of Thiruvallam) and flows around the Edayar island on its way to the Poonthura estuary. Both the rivers carry large quantities of raw sewage discharged from city drains. The heavily polluted Parvathy Puthanar canal joins the river at Munnattumukku, near the Poonthura coastal village.

The flow of water on the western side of the island is blocked from heavy silting at Munnattumukku and accretion of sea sand at Kunnumanal. During high tide, seawater from the estuary surges up to Thiruvallam through the eastern side of Edayar. When the tide ebbs, the dirty water from the Parvathy Puthanar rushes in, covering the upstream portions up to Thiruvallam and beyond.

Scientists and environmentalists feel that the pollution of the river water has to be tackled at point sources on a watershed approach with the active involvement of local bodies and the public. They highlight the need for a comprehensive master plan to restore the river.

An environmental monitoring programme on water quality carried out by the Kerala State Council for Science, Technology and Environment (KSCSTE) had revealed heavy pollution in major stretches of the river, with Thiruvallam being the most contaminated reach. KSCSTE is preparing to take up a project to restore an 18-km stretch of the river. “The concept paper has been approved and an action plan is being prepared. The project will be implemented with the help of the Thiruvananthapuram Development Authority and other agencies,” says V.N. Rajasekharan Pillai, executive vice president, KSCSTE.

The Kerala State Biodiversity Board (KSBB) is also embarking on an initiative to create a green belt along the banks of the river. “The project seeks to plant mangroves and bamboo to shore up the banks. It will support the river restoration programme,” KSBB Chairman Oommen V. Oommen says.