Garbage piling up on the banks of Yediyur lake in Bangalore
Yediyur lake among most polluted
By Daksha Hathi
DH News Service
BANGALORE, Jan 9
Yediyur lake is the latest to join the gloomy list of the most polluted lakes in
Bangalore, while Bannerghatta lake may be the only remaining clean lake, according
to the Indian Institute of Sciences, which has done a comparative study of these
two city lakes.
The Centre for Ecological Sciences of the IISc which did a one-year study of the
one hectare Yediyur lake, (funded by the Ministry of Environment and Forests)
comparing it with Bannerghatta lake has made an urgent appeal for the restoration
of the former, which is severely polluted. Scientists Kiran R, Deepa R S and
Ramachandra T. V. of the Centre for Ecological Sciences in their report have
expressed grave concern over the fact that Yediyur in Jayanagar is now a cesspool
clogged with domestic and industrial sewage from solid wastes.
The CES monitored Yediyur`s water quality for a year and noted that the lake waters
were greenish black and loaded with high chloride levels of 109.8mg/l, hardness due
to domestic and industrial washings, total dissolved solids ranging from 208 to 428
mg/l and other impurities due to food wastes and detergents. Yediyur also had
persistent blooms of toxic blue-green algae. Its values of Biological Oxygen Demand
(BOD),Chemical Oxygen Demand (COD), chlorides and other impurities were much higher
than the safe limits set by WHO, Central Pollution Control Board and NEERI.The high
concentration of chlorides is an indicator of pollution due to high organic wastes
of animal or industrial origin,their report says.
In contrast, the two hectare Bannerghatta lake, also known as Deepakanahalla,
located within Bannerghatta National Park, was found to be non-polluted, due to its
protected surroundings. It had better water quality and a greater diversity in
plankton ( which indicates water purity. ) Prof Ramachandra told Deccan Herald,
Banerghatta lake is an example of a protected lake system which preserves its purity
as there are no sources of pollution to threaten it. Its water was seen to be clear
and free from odour throughout the study period. This lakes suspended solids did not
go above 132 mg/l and even dissolved solids were well within the WHO limits. The
scientists noted that this lake satisfies drinking water quality standards.
Yediyur, on the other hand, is giving out a foul smell at several points and shows
high COD, BOD and Chloride content. It has become a breeding ground for mosquitoes.
There is an immediate need to check its pollution,he said.
At its recent symposium Lake 2000 the CES also noted that three other lakes need
urgent attention. Ulsoor lake has become so polluted that it is incapable of
purifying itself naturally, as shown by a two month study done by H. V. N. Rao.
Madivala Lake which was analysed by C Jayaram for a day was also found to be
polluted in spite of being partially restored. Lastly, scientists R Venkatraman and
K R Narayana Iyengar monitored the pollution of Kempambudhi lake and found it to be
heavily contaminated due to sewage. Yediyur and Bannerghatta lakes were tested with
the assistance of the Karnataka State Pollution Control Board.