Bellandur Lake is located n the south-eastern portion of Bangalore metropolitan region with spatial extent of 370 hectares and a catchment area of 158.5 sq.km. (Figure 1) comprising the Koramangala and Challagatta valleys. These lakes were originally built to meet the domestic and irrigation demands in the region Their current storage capacity is estimated to be 5.5 M c m. Today, because of unplanned urbanization, the storm water inlets feeding the lake, mostly carry raw sewage. In addition, of course, during the monsoon, the lake receives storm runoff.