As the State government challenges the 75 metre buffer limit around lakes set by the National Green Tribunal (NGT), a geo-spatial analysis by researchers of Indian Institute of Science (IISc.) of Bellandur and Varthur lakes has shown that built-up areas are increasing around the two severely polluted lakes.
Using a 75m buffer, the Energy and Wetlands Research Group, Centre for Ecological Science (IISc.) found that the amount of built-up area shot up from 0.5% of Bellandur’s buffer to 45% in 2016 at the cost of agriculture and horticulture traditionally practised there.
In Varthur’s buffer zone, built-up areas increased from 5% to 30% in 15 years, shows the technical report published in December.
In both lakes, tank bed encroachment has increased as debris and soil were dumped into the lake.
While the BDA’s masterplan mandates a buffer zone of 30 metres, the NGT had extended this to 75m retrospectively. The State government had challenged this in court while Bruhat Bengaluru Mahanagara Palike (BBMP) has discussed in its council multiple times to reduce the buffer zone to 30m.
According to T.V. Ramachandra, author of the report and also part of the technical committee to oversee rejuvenation of the lake, the move to reduce buffer zones was senseless.
The report shows that while the 30m buffer zone around the lake has a capacity to store 0.6 million cubic metres of water, keeping a 75m buffer zone would double the storage to 1.2 million cubic metres. The extended buffer in upstream lakes of Bellandur will allow storage of 7.1 million cubic meters of water, which is nearly triple the storage when compared to a buffer zone of just 30m.
Valleys encroached
The report also shows that the wetlands forming the valley between Bellandur and Varthur lakes has considerable shrunk. In 2002, just as the software park in ITPL was taking shape, over 98.5% of this valley was wetlands and agriculture. This has decreased to 25.68%, with the remaining being residential areas.
“This rampant growth in the valley zone has removed lakes and rajakaluves, which altered the function of the natural system of cleansing water, recharging groundwater,” states the report.
Consequently, rajakaluves reduced from 25-35m to just 5-8m.
