Rain havoc and death of city lakes

There were nearly 200 natural lakes and natural drainage system which allowed rain water to drain in lakes in the undulating topography of Bengaluru city. The overflow from the lake at higher altitude joined immediate next lake th-rough natural course and so on.

The series of lakes along the Bannerghatta Road, Old Airport Road and up to Varthur Lake is Koramangala-Challaghatta Valley and overflow from Varthur lake joins Pennar River. With the development of civic facilities and growth of the city, natural drains are disturbed. Storm Water Drains (SWDs or Raja Kaluves) were also established, between two lakes for drainage of water in the valley.

The unprecedented growth in the city also resulted in illegally occupying lake lands and SWDs. Lake lands were acquired and developed for many civic facilities such as schools, hospitals, play grounds, bus stations etc, which disturbed natural drainage pattern of the city. Finally, many lakes died and the number reduced to one third.

Although proper sewer lines were provided in years in the BBMP areas, adjoining areas from seven City Municipal Councils (CMCs) did not have proper arrangement of draining of sewage and treatment. In many cases, the discharge was directly in to the SWDs.

Totally, 1,000 million litre day (MLD) sewage is generated in BBMP area and hardly there is facility to treat 40% of it. Thus, 600 MLDs of untreated sewage flows in these lakes every day. This causes massive pollution and health hazard for the people.

Discharge of untreated sewage and industrial affluent, dumping of construction waste, encroachments on lakes and SWDs, flow of silt and sludge in the lakes lowers the water storage capacity year by year.

As water storage capacity is limited – and there are continuous rains for 4-5 days and that too 100 mm of rains in four hours – water from lake and SWDs would flow to low lying houses of the catchment area. This has what happened in the recent rains in Bengaluru. Madiwala, Hulimavu, Yemlur, Bellandur and Akshayanagar lakes overflowed and ground floor of many houses were under five feet water.

During September-October 2005, a similar emergency had arisen when SWDs connecting Sarakki and Puttenahalli lakes was breached following heavy rains and water gushed into low lying houses.

I was the chief executive officer of the Lake Development Authority then and my residence telephone never stopped ringing that night. Rescue personnel and boats were rushed to the spot for the assistance of the sufferers.

Clearing encroachments
High level team of the state government visited the spot and it was resolved to clear all encroachments of lake beds and storm water drain. It was also decided to restore the original width of storm water drain, de-silt and repair it properly.

After a lapse of 10 years I find that SWD leading to Madiwala Lake still requires five to six years for its completion. Pourkarmikas of BBMP, while sweeping the road, are often found to push the silt, leaves and polythene into the uncovered length of side drains, thereby chocking it completely. All these side drains require maintenance. The BBMP must rise to the occasion and prepare fully for next eventuality.

To increase the capacity of water storage, desilting and removal of sludge is also required to be carried out for these lakes on a regular basis. There is bio remedy method for clearing the pollution of the lake. One such project costing Rs 5.5 crore was taken up by my predecessor in LDA in 2004-05 for Bellandur Lake.

The project was started with supply of oxygen from power sources on shores of entire 500 acres of water-spread area. However, the entry of untreated sewage from different ingression points could not be prevented.

The water quality did not
improve and application of biological feeders of organic sediments (oil of phenolic compounds and suspended solids), vegetable enzymes and polymer bacteria growth substrate was put off. Some 200 MTs of three substances would have consumed the sludge and converted into gaseous forms.

The substances were transported to a storage building in Madiwala Lake and is unutilised so far. The potency of these substances must have been lost. If the capacity of lakes and SWDs are improved, such exigency can be prevented.

(The writer is retired Principal Chief Conservator of Forest, Karnataka)