A report on the quality of water in 106 lakes in Bengaluru Urban and Rural districts published by non-government organisation ActionAid India found that the water in none of the lakes sampled was fit for drinking or bathing.
ActionAid consolidated and analysed lake sample collection findings by the Karnataka State Pollution Control Board (KSPCB) for a 24-month period between January 2019 and December 2020.
The data was consolidated on the basis of Water Quality Index (WQI) under different classes. Most of the lakes fell either in Class ‘D’ category, which is fit for propagation of wildlife and fisheries, and others in ‘E’ category, where the water can only be used for irrigation and industrial cooling purposes.
Classification of lakes
Of the 1,684 samples collected by KSPCB over the last year from lakes, 1,191 samples fell under ‘D’ category, and 489 in the ‘E’ category. The lakes were further classified as satisfactory (S) or unsatisfactory, according to the WQI. Here, too, the findings were discouraging: only 0.24% of the samples were marked S.
Within ‘D’ class, a total of 24 lakes were found to be ‘better performing’.
“As per the National Restoration Goals (Ponds, Lakes and Rivers), if a water sample from a particular lake falls in the same class six out of eight times (75%) it is tested, then it considered as a consistently performing lake,” said Raghavendra B. Pachhapur, ActionAid Association, India Programme Manager.
The top five lakes under the category of better performers were Devarakere Tank, Annaiappa Tank, Lalbagh Tank, Yediyur Lake and Kempambudhi Lake. Twelve lakes fell under the category of worst performers, including Shivapura Tank and Karihobanahalli Lake in Peenya, Gangondanahalli Lake and Chikkabanavara Lake in Dasarahalli, and Viswaneedam Lake.
Quality of data
Incidentally, in February this year, CSIR-National Environmental Engineering Research Institute (NEERI) had submitted a report to the High Court showing that of the 210 lakes it had surveyed, at least 14 in the Bruhat Bengaluru Mahanagara Palike (BBMP) limits were of ‘excellent’ quality and could be used for drinking. One of the lakes listed was Puttenahalli.
However, data from KSPCB as collated by ActionAid, showed that samples fell in the ‘D’ category when tested 14 times last year, and in the ‘E’ category 6 times. Samples were not collected from Puttenahalli in March, April, May and June 2019.
Lake valley systems
The ActionAid report also analysed data from lake systems: Koramangala - Challaghatta valley with 84 lakes; Hebbal - Nagavara valley, which has 55 lakes; Vrishabhavati valley system that covers up to 37 lakes and Arkavati with 15 lakes.
The Koramangala-Challaghatta system had the best performance, with only 16% of the samples in the ‘E’ category.
“The Arkavati valley was observed to be the worst as 53% of the collected water samples were identified as D and 47% under E,” stated the study.
