Bangaloreans were once caught in the mystery over the drying up of lakes while rains flooded the low-lying areas. But now it is clear that both the issues have their origin in the encroachment of lakes,  their catchment areas and storm water drains, as a study by the Indian Institute of Science (IISc) reveal.

Encroachment of lakes has become a common thing, but the land sharks have not even spared the storm water drains and catchment areas. Over 50 percent of lakes are drying up due to this and is resulting in urban floodings, according to the study conducted by the Energy and Wetland Studies Research Centre, Centre for Ecological Sciences,IISc.

The study which analysed various lake beds have found that the natural drainage channels and the catchment areas have been encroached by land mafia in connivance with Government machinery.

“The downstream of Nagavara has been encroached. Even the drain connecting the Sankey lake is encroached, A major portion of the Begur lake catchment area has disappeared. It is not one story, but all the City wetlands are facing similar problem,” says Dr T V Ramchandra, Senior Scientist, Energy and Wetland Research Group, CES, IISc.

Pointing out that the water storage capacity of the lakes has decreased in recent years, the study says that even a slight rainfall now leads to water logging due to the encroachment of drains.

The report says that the changes related to flooding has become a routine after 2000. Even a 30 mm rainfall for half an hour will lead to water logging. The connectivity between Yelchenhalli Kere and Madivala, and between Madivala and Bellandur has been lost due to the encroachment.

In the Bellandur- Ulsoor Catchment area, with six lakes of Sankey, Ulsoor, Chalghatta, Chinanagara and Varthur, out of the total 240 Million cubic meter of rainfall yield, only 90 million cubic meter is percolated and 150 million cubic meter overflows, depriving the lake of most of the water. A major portion of the water cannot flow downstream due to disruption of natural drainage.

The story is not much different in Madivala- Varthur Catchment area with 14 lakes. Now,  BBMP is trying to redesign the SWDs at a cost of Rs 950 crore for the core city and a whopping 6,600 crore to build new SWDs in the newly added seven City Municipality Council regions.