Karnataka: Sewage main cause for low oxygen in lakes, says KSPCB

The National Green Tribunal, while hearing a suo motu case, said over 10% of the city’s 117 lakes recorded anoxic (very low/absent dissolved oxygen) conditions.

Bengaluru: The Karnataka State Pollution Control Board (KSPCB) has reiterated that the entry of sewage is the primary cause of pollution of lakes in the city.

The National Green Tribunal, while hearing a suo motu case, said over 10 per cent of the city’s 117 lakes recorded anoxic (very low/absent dissolved oxygen) conditions.

Dissolved oxygen (DO) was below detectable levels (< 0.3 mg/litre) in 12 lakes as well as in Dakshina Pinakini river.

Continuous monitoring by the board since April 2024 showed variations in DO levels. Low DO is detrimental to aquatic life. Except at Varthur, where water has been diverted for rejuvenation, sewage inflow and decay of organic matter were found to be main causes of low DO.

“The board submits that the low DO levels recorded in the identified lakes and the river are primarily attributable to inflow of untreated sewage,” it said. To address the issue, KSPCB proposed 100% underground drainage in catchment areas and other measures.