Restored lakes undone by poor maintenance: IISc

Of the 24 restored water bodies in the city found to be of ‘very poor water quality’ by an Indian Institute of Science (IISc) study, many have slipped due to poor maintenance, the unchecked inflow of sewage and restoration restricted to only ‘beautification.’

Rejuvenated by the Bruhat Bengaluru Mahanagara Palike (BBMP), the 34.82-acre Herohalli Lake in Sunkadakatte is today heavily polluted for an obvious reason: the IISc research team found that about seven million litres per day (MLD) of sewage water flows in.

The lake had been restored with a pathway, lighting facilities and a garden. But a 1.5 MLD-capacity sewage treatment plant (STP) was planned only after the high pollution due to unchecked sewage entry rendered the water fit only for irrigation and industrial cooling. The water has turned green due to algal growth.

Lake area encroached

Located at the junction of Jalahalli and Mathikere, the 67.02-acre JP Park Lake is one of the biggest lakes restored by the Palike. However, the IISc study discovered that the lake area had considerably shrunk due to encroachments.

Although the restored lake supports fish and bird populations, the study found big problem areas: “Entry of untreated sewage, disposal of plastic bags containing food and over-feeding of fish.”

Classifying the water quality as ‘very poor,’ the study noted: “Lake water is in high turbid condition. Water is alkaline due to algal growth. Algae had removed nutrients in the lake water through uptake for their growth and reproduction.”

The 9.22-acre Puttenahalli Lake in the Koramangala-Challaghatta Valley was restored in February 2017 with active participation from the local residents. The much-lauded efforts by the Puttenahalli Neighbourhood Lake Improvement Trust (PNLIT) had become a model for many other lake rejuvenation projects.

However, the study observed: “Entry of untreated sewage, slum dwellings on one side of the lake, poorly maintained.” It also drew attention to the fish kills, the alkaline pH and organic contents due to sewage inflow and high turbidity.

Arresting the sewage inflow will address much of the lake’s problem, said Dr T V Ramachandra, who had led the research for the IISc study.

Spread over 48 acres, the Kaikondrahalli Lake in the K-C Valley is another waterbody categorised as ‘very poor.’ Post restoration, the lake has been used by local residents for bathing, washing and even drinking. However, the study team found ample evidence of sewage entry and foam formation at the inlet points.