Sunday, 1 June 2014

Saving a lake from choking to death - Destination Bangalore

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.
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





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