The findings of the study entitled, ‘Present status of lakes and tanks in and around Bangalore’, carried out by the Central Environmental Laboratory of KSPCB, from January 2008 to October 2009 were made available on Tuesday.
In all, 55 lakes and tanks were analysed for the study and only ten of them were found to be in good condition, says Dr Lokeshwari, Scientific Officer at the laboratory, who carried out the study. Thirty-two of the lakes are in a condition that can be described as ‘bad’ while 13 are in ‘worst’ condition, she says.
The lakes earning the ignominy of being in the worst category are Nayandahalli tank, Madavara tank, Bellandur lake, Doddanakundi tank, Karihobanahalli lake, Dasarahalli tank, Varthur lake, Haralakunte lake, Somasundra Palya lake, Puttenahalli Lake, Veerapura tank, Annayappa tank and Uttarahalli Doraikere. Those in the bad category include Madiwala tank, Ulsoor lake, Agaram lake, Nagavara tank and Parapanna Agrahara lake.
There is an urgent need to rejuvenate them in order to maintain the delicate ecological balance in the City, observes Gowdar, Member Secretary of the board.
Elaborating on her study, Dr Lokeshwari said that the assessment was done on the basis of 15 parameters. The chief requirement for a lake to be considered in satisfactory condition was that the Dissolved Oxygen (DO) level must be more than 4 milligrams/litre while its Biochemical Oxygen Demand (BOD) less than 3 mg/litre.
“If the DO is found more than this limit or if the BOD is lesser than the permissible limit, it causes mass death of fish and promotes algal growth contaminating the water.”
The Scientific Officer also lamented the fact that 15 out of the lakes and tanks studied were developed under different funding programmes by various organisations.
“Unfortunately, seven of them have gone back to their bad condition due to poor maintenance,” she says.
Madiwala lake, Kempambudhi, Ulsoor, Byrasandra, Bellandur, Agaram and Nagavara lakes fall into this category.
Huge discharge of industrial wastes and sewage into rivers, ponds and lakes are the main reason why the water bodies were polluted. Pollutants like heavy metals, cyanides, boicides and other organic and inorganic compounds that prove toxic to aquatic organisms.