Najafgarh drain  The Najafgarh drain or Najafgarh nalah ("nalah" in Hindi means rivulet or storm water drain), which also acts as Najafgarh drain bird sanctuary, is another name for the northernmost end of River Sahibi, which continues its flow through Delhi, where it is channelized, and then flows into the Yamuna. Within Delhi, due to its channelization for flood control purposes, it is now erroneously called "Najafgarh drain" or "Najafgarh nullah." 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 classifies this drain, with 13 other highly polluted wetlands, under category ‘‘D’’ for assessing the water quality of wetlands in wildlife habitats. This drain was widened as a flood control drain linking the Najafgarh lake to the river Yamuna, thus completely draining the once huge and ecologically rich Najafgarh Lake, famous for its wetland ecosystem, waterbirds and wildlife. Within the National Capital Territory of Delhi (NCT), this channelized waterway—misclassified, misnamed as a mere drain ("Najafgarh drain or nullah")--is, in fact, the continuation of the Sahibi River and an elongation of the Najafgarh jheel Lake. During the 1960s and before, the rain-fed Sahibi River, which originates in the Jaipur District of Rajasthan, passing through Alwar District in Rajasthan and Gurgaon District in Haryana, entered Delhi near Dhansa and spilled its overflow in the Najafgarh Lake basin. This overflow created a seasonal lake; an area of more than was submerged in some seasons. This water then continued to flow on the other side, forming a tributary of the River Yamuna. In the following decades, this Sahibi River flow reaching the Dhansa regulators was channelized by digging out a wide drain and connecting it directly to the River Yamuna. This channelization also completely drained off the seasonal Najafgarh Jheel that had formed there previously. The channelized drain from Dhansa regulators to Keshopur Bus Depot on Outer Ring Road is wide with thick and high embankments.