Below this, the discharge of wastewater in Delhi through 15 drains between Wazirabad barrage and Okhla barrage renders the river severely polluted. The water quality in "Upper Yamuna", as 375 kilometres (233 mi) long stretch of Yamuna is called from its origin at Yamunotri to Okhla barrage, is of "reasonably good quality" till Wazirabad barrage in Delhi.
Beyond that point the Yamuna is joined only by the Somb, a seasonal rivulet from Haryana, and by the highly polluted Hindon River near Noida, so that it continues only as a trickling sewage-bearing drain before joining the Chambal at Pachnada in the Etawah District of Uttar Pradesh. At the Hathni Kund Barrage, its waters are diverted into two large canals: the Western Yamuna Canal flowing towards Haryana and the Eastern Yamuna Canal towards Uttar Pradesh. It has an annual flow of 97 billion cubic metres, and nearly 4 billion cubic metres are consumed every year (of which irrigation constitutes 96%). Nearly 57 million people depend on the Yamuna's waters, and the river accounts for more than 70 percent of Delhi's water supply. It helps create the highly fertile alluvial Yamuna-Ganga Doab region between itself and the Ganga in the Indo-Gangetic plain. After passing Paonta Sahib, Yamuna flows along the boundary of Haryana and Uttar Pradesh and after exiting Haryana it continues to flow till it merges with the river Ganga at Sangam or Prayag in Allahbad (Uttar Pradesh). From Uttarakhand, the river flows into the state of Himachal Pradesh. It crosses several states: Haryana and Uttar Pradesh, passing by Uttarakhand and later Delhi, and meeting its tributaries on the way, including Tons, Chambal, its longest tributary which has its own large basin, followed by Sindh, the Betwa, and Ken. According to popular legends, bathing in its sacred waters frees one from the torments of death. In Hinduism she is the daughter of the Sun Deva, Surya, and the sister of Yama, the Deva of Death, hence also known as Yami. Like the Ganga, the Yamuna is highly venerated in Hinduism and worshipped as the goddess Yamuna. It merges with the Ganga at Triveni Sangam, Allahabad, which is a site of the Kumbh Mela, a Hindu festival held every 12 years. Originating from the Yamunotri Glacier at a height of 6,387 metres (20,955 ft) on the southwestern slopes of Banderpooch peaks of the Lower Himalaya in Uttarakhand, it travels a total length of 1,376 kilometres (855 mi) and has a drainage system of 366,223 square kilometres (141,399 sq mi), 40.2% of the entire Ganga Basin. The Yamuna ( Hindustani: pronounced ) is the second-largest tributary river of the Ganga and the longest tributary in India. Giri, Baghain, Chambal, Betwa, Sindh, Ken Tons, Hindon, Hanuman Ganga, Sasur Khaderi