'Drone survey of city lakes will not detect encroachments'

Tasked with the preparation of a master plan to rejuvenate Bengaluru’s 210 lakes, the Hyderabad-based National Environmental Engineering Research Institute has invited contractors to conduct a drone-based survey. But environmentalists say this will neither detect the rampant lake encroachments nor help build a Digital Elevation Model (DEM).

The institute, attached to the Council of Scientific and Industrial Research (CSIR), had floated a Request for Proposal (RFP) inviting a third party to carry out the drone survey for all the lakes and prepare the master plan. A copy of the RFP, accessed by DH, clearly states this.

As Nagesh Aras from Friends of Lakes (FoL) put it: “This is a one-time massive effort that will decide the fate of all lakes and all three valleys. If anything goes wrong here, correcting it will be extremely expensive; and we will have to live with the problems for a long time to come.” Aras said: “To detect encroachment, we need a ground survey and cadastral maps as reference. A drone cannot do this. To create a DEM of the area, either ground survey or remote sensing is needed. For more accurate DEM, we need a LIDAR survey.”

The RFP proposed to work on lakes one-by-one. “There is no proposal to establish the water balance of the valley or catchments, or to plan and promote water harvesting in the area, or identify floodplains to avoid/mitigate frequent floods in the city,” Aras points out.

The Terms of Reference ignore lake issues linked to encroachments; inflow of domestic/industrial sewage and the need for sewage separation and diversion downstream. There is also no mention of the encroachment of the stormwater drains that feed or drain the lakes. In January, NEERI had certified that water quality in 40% of the 45 city lakes it examined was ‘good’ for domestic and irrigation purposes, but not for drinking.