 Varthur Lake, which has an area of is the second largest lake in Bangalore city and also one of the most polluted lakes in Bangalore.Its ecosystem is under continuous degradation because of sewage water from Bangalore entering the lake from Bellandur Lake, further upstream.This is a man-made lake, built by the Ganga kings over thousands of years ago for agriculture and domestic uses but now the lake is receiving 40% of the sewage water from Bangalore for over 50 years resulting in eutrophication.