Cooum check-dams act as pollution traps. (pic for story)
Because different types survive under different water conditions, “Diatoms are good indicators of pollution. Because they are located before the tributary joins the Cooum, he said the check dams could be intervention points.
These pollutants could affect groundwater in surrounding localities,” said Prof Nagaraj Subramani, corresponding author. Our findings show that the check dams are also retaining pollutants in the sediment.
Researchers said the structures trapped organic matter, nutrients, salts and plastics, while diatoms (algae) shifted from types that thrive in cleaner water to pollution-tolerant types, as water slowed down in these spots, allowing material to settle in sediment. Chennai: Check dams across the Cooum basin could serve as strategic points to monitor and tackle pollution, a study into one of its tributaries has found. A key finding was that upstream water was relatively clean, with diatoms associated with better water quality, while pollution increased and sediment accumulated pollutants and plastics towards the urban check dam .
“Around 10 years ago, a march along the Cooum identified about 880 sewage inflow points.
“Pollution stopped here means cleaner water flowing into the main river,” he said, adding that cleaning feeder streams should be part of Cooum restoration. Environmental activist G Sundarrajan said pollution must be stopped at source. A partial recovery in diatom diversity was found in a free-flowing middle stretch, linked to better water movement, before pollution-tolerant types increased again downstream. The first priority must be to stop sewage from entering the river. We have spent thousands of crores on making Chennai beautiful, but we are still not getting the results. We need delivery on the ground, not more projects on paper.”