High Quality Content by WIKIPEDIA articles! The Najafgarh drain or Najafgarh nallah (nallah in Hindi means rivulet or storm water drain) is just another name for the River Sahibi which continues its flow through Delhi where it is channelized, it is a tributary to River Yamuna in which it outfalls here. Within Delhi due to its channelization for flood control purposes it is now erroneously called "Najafgarh drain" or "Najafgarh nallah"`, it gets this name from the once famous and huge Najafgarh Jheel (lake) near the town of Najafgarh in southwest Delhi and within urbanized Delhi it is the Indian Capital’s most polluted water body due to direct inflow of untreated sewage from surrounding populated areas. A January 2005 report by the Central Pollution Control Board clubs this drain with 13 other highly polluted wetlands under category ‘‘D ’’ for assessing the water quality of wetlands in wildlife habitats.