The Yamuna (jəmʊnɑː) is the second-largest tributary river of the Ganges by discharge and the longest tributary in India. Originating from the Yamunotri Glacier at a height of about on the southwestern slopes of Bandarpunch peaks of the Lower Himalaya in Uttarakhand, it travels a total length of and has a drainage system of , 40.2% of the entire Ganges Basin. It merges with the Ganges at Triveni Sangam, Prayagraj , which is a site of the Kumbh Mela, a Hindu festival held every 12 years.
Like the Ganges, the Yamuna is highly venerated in Hinduism and worshipped as the goddess Yamuna. She is the daughter of the sun god, Surya, and the sister of Yama, the god of death, and so she is also known as Yami. According to popular Hindu legends, bathing in Yamuna's sacred waters frees one from the torments of death.
The river crosses several states such as Haryana, Uttar Pradesh, Uttarakhand and Delhi. It also meets several tributaries along the way, including Tons, Chambal, its longest tributary which has its own large basin, followed by Sindh, the Betwa, and Ken. From Uttarakhand, the river flows into the state of Himachal Pradesh. 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 Ganges at Sangam or Prayag in Prayagraj (Uttar Pradesh). It helps create the highly fertile alluvial Ganges-Yamuna Doab region between itself and the Ganges in the Indo-Gangetic plain.
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 has an annual flow of 97 billion cubic metres, and nearly 4 billion cubic metres are consumed every year (of which irrigation constitutes 96%). 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.