CHENNAI : Trash booms on the Cooum River have been effective in preventing plastic from entering the sea. However, irregular cleaning of the waste caught by the netting slows the flow of water and boosts water hyacinth growth.Hyacinth infestations are seen in the slow flowing Adyar and Cooum Rivers in summer. But with the trash booms and further slowing flow of water, hyacinths are seen in stretches before the trash booms.
The city corporation has placed trash booms in seven out of the nine proposed locations for the Cooum River. The Adyar River is yet to get its first trash boom. “The trash booms are cleaned every 15 days or when necessary,” said an official involved in the restoration of the Cooum River. But, this is ample time for a hyacinth colony to increase its size by 50 per cent.
This means hyacinth washed down from other stretches of the water can also grow exponentially at these stretches before clogged trash booms. Water hyacinth reproduces through runners and stolons which form daughter plants. The seeds remain viable for 20 years, making it hard to eliminate from an aquatic environment once infestation begins.
Corporation officials claim regular cleaning is done to ensure hyacinth and waste is removed. “Inputs are given from the zonal level after regular inspections and machines are sent,” said a senior official. However, the workers on ground tell a different story. “Cleaning is given importance once before monsoon to ensure water flows freely into the ocean. Plastic waste is also collected during this time so cleaning is done on alternative days,” said a machine operator.
The corporation only has three machines for clearing waste and with the number of trash booms set to double soon, workers say that new machines will be required to ensure regular clearing of waste. Botanists believe hyacinth has some benefits. “Water hyacinth absorbs heavy metals and sulphur from polluted water,” said G Ebenezer, head of the department of plant biology and biotechnology.However, the hyacinth removed from the rivers is directly sent to the landfills, which means the heavy metals will still seep into the soil.
Water hyacinth is an invasive weed which reduces oxygen content in water and affects aquatic systems. Stagnant, polluted water is a conducive environment for this plant. This is one of the reasons most lakes in Chennai are infested with this weed.