It describes the efforts undertaken by the Karnataka State Pollution Control Board to launch a programme to monitor the water quality of some of the lakes in Bangalore so as to focus the attention of concerned governmental organisations to take up remedial measures to safe guard the water bodies of the "Garden City". 

The sources of pollution in lakes are mainly identified as:

• Sewage entry from human settlements in catchment area
• Effluent entry from the industries located on the upstream of the lakes
• Erosion of soils carrying nutrient from the upstream
• Ingress of sewage and industrial effluent which contains nutrients
• Runoff from surrounding areas which carries with it silt and nutrients
• For other human activities such as bathing, washing, disposal of garbage etc
• Dumping of debris from construction activity
• Draw off of water from the lake
• Immersion of idols during some festival

The Karnataka State Pollution Control's Research and Development Wing took up monitoring of lakes/tanks in around Bangalore metropolitan area to know the quality of the water body and also the waste water discharges into the water bodies. 44 lakes/tanks in and around Bangalore metropolitan area out of 60 lakes/tanks were covered in the first phase while around 16 lakes/tanks were monitored in the second phase of the project.

The samples were analysed as described in standard methods for the examination of water and waste-water. The analysis found that urbanisation had produced a long term impact on the lake ecosystem and most of the lakes in Bangalore were found to be contaminated by sewage mixing with lake water. Water hyacinth in many lakes had taken over with thick green crust. The weeds obstructed sunlight and reduced self purification action through photosynthesis. To maintain and prevent deterioration of water bodies, the following rehabilitation measures were proposed:

• De-silting
• De-weeding
• Prevention of sewage and industrial effluents into the lake and construction of suitable effluent treatment plants

The report identified the need for the following organisations to put their efforts in mitigating lake pollution:

• Bangalore Water Supply and Sewerage Board
• Bangalore Development Authority
• Bangalore Metropolitan Regional Development Authority
• Bangalore Mahanagara Palike
• Zilla Panchayat
• Forest Department

A paper based on this report was presented at the proceedings of Taal 2007: The 12th World Lake Conference and is available at this link.

A copy of the report can be downloaded below :