Saving a lake from
choking to death - Destination Bangalore
Plants to eat up pollutants, fish to enhance water quality and silt that’s turned into a joggers’ track keep Hebbal Lake in Bangalore safe from garbage dumpers and greedy land sharks
When you zip past the sparkling Hebbal
Lake on your way to the Bangalore International Airport, you wouldn’t imagine
that it was once covered by layers of water hyacinth, filth and sewage, would
you? Migratory birds nest in trees on its green islands, joggers pound the 7-km
track on the lake’s periphery and the lake itself showcased as a tourist
attraction. How did this magical makeover happen?
Rejuvenation may sound like a fancy word but truth be told, it boils down to simple, practical, common-sense ideas. Here’s how we achieved the impossible. But first a quick mention of the project that made this happen: The Indo-Norwegian Environment Programme (INEP) supported the rejuvenation of three lakes in the City: Hebbal, Madiwala and Dodda Bommasandra near Vidyaranyapura. I chose to work on Hebbal Lake first because of its strategic location: it’s on National Highway 7 and it has a single water inlet channel which makes the clean-up drive relatively easy. Upstream are HMT Layout, Tata Nagar and Vidyaranyapura, and downstream is Nagavara Lake and Manyata Tech Park.
Rejuvenation may sound like a fancy word but truth be told, it boils down to simple, practical, common-sense ideas. Here’s how we achieved the impossible. But first a quick mention of the project that made this happen: The Indo-Norwegian Environment Programme (INEP) supported the rejuvenation of three lakes in the City: Hebbal, Madiwala and Dodda Bommasandra near Vidyaranyapura. I chose to work on Hebbal Lake first because of its strategic location: it’s on National Highway 7 and it has a single water inlet channel which makes the clean-up drive relatively easy. Upstream are HMT Layout, Tata Nagar and Vidyaranyapura, and downstream is Nagavara Lake and Manyata Tech Park.
The 64.5 hectare lake was putrified,
covered with water hyacinth and had no visible water sheet. It was as if one
could walk on it! Sewage from all the nearby layouts were discharged into this
lake. With funds from INEP , help
from experts in water conservation and cooperation of the Forests Department,
the lake became a living, breathing entity.
Ø We
identified the source and entry points of sewage discharged into the lake and
found that domestic sewage discharge was heavy, leading to water hyacinth
growth. Water recharged into the ground was full of contaminants, including
heavy metals.
Ø The
lake was isolated from the sewage and the storm water flow was regulated. On
the northern side of the lake is land belonging to the army. Skirting this
land, we built a diversion canal downstream. The upstream sewage flow now
bypasses the lake and flows into the canal and then into Nagavara. Ideally, it
should have gone into a sewage treatment plant. This was a temporary solution,
no doubt, but we shifted it downstream to show that an urban lake can be
restored. There’s a lot of science behind this. Segregation sewage and
rainwater has to be done carefully.
Ø A
wetland system was created within Hebbal lake, where plastics, bottles and
large objects can be removed through filtration. Biological purification was
achived using hydrophytic plants which absorb dissolved pollutants and toxins.
The wetland also acts as a silt trap. There are vents from which water can flow
from a certain height to the main lake. This ensures that relatively clean
water is made cleaner.
Ø We
desilted the lake and removed
accumulated sludge and sediments. This process took us three years (2000-2003)
because the sludge had accumulated over 40 years! The obvious question we faced
was: Where would the millions of tonnes of sludge go? We couldn’t dump it just
anywhere! It wasn’t fertiliser-quality because it was full of detergents, heavy
metals, toxins etc. It was too expensive to transport to a faraway landfill.
Then, we had a brainwave: the lake was being developed as a recreation centre.
So, we created a jogging track of 7 km with this silt! Over that we put good
soil and planted ornamental plants, grass etc.
Ø We
also created islands using the silt. Here, we planted fruit-bearing trees. The
islands were so designed that dogs and rodents couldn’t access it. It became a
nesting place for birds such as purple moorhens, cormorants, Brahminy kites,
darters, kingfishers, weaver birds, purple herons, grey herons, pond herons
etc.
Ø We
strengthened the existing bunds and wetlands with stone pitches.
Ø A
chain-link fence was built to protect the lake from garbage dumpers.
Ø Fish
culture and boat jetty services were introduced. The fish enhanced water
quality and yield revenue while the pedal boats were for recreation for the
public and churned the water, thereby aerating it.
Ø A
waste weir was built to maintain water level in the lake. The weir also avoids
breaching and flooding.
Ø As a
tribute to people’s power, a citizens’ committee was formed. The Hebbal Lake
Development and Protection Group, headed by Former Chief Secretary of
Government of Karnataka, made sure the lake stayed clean and safe.
Ø
Total investment on restoration: Rs 3
crore.Returns on investment: Immeasurable, because after desilting the lake,
borewells in the vicinity were recharged and began overflowing!
Part
of Lake before rejuvenation
|
Development
of wetland system for pre treatment
Fresh
Rainwater collected in Hebbal Lake after rejuvenation
Island inside Hebbal Lake and City development on the foreground
Boat
jetting for recreation in Hebbal Lake
Winged
visitors to Hebbal Lake, Bangalore