The Yamuna is the second-largest tributary river of the Ganga and the longest tributary in India. Originating from the Yamunotri Glacier at a height of 6,387 metres on the southwestern slopes of Banderpooch peaks of the Lower Himalaya in Uttarakhand, it travels a total length of 1,376 kilometres and has a drainage system of 366,223 square kilometres, 40.2% of the entire Ganga Basin. It merges with the Ganga at Triveni Sangam, Allahabad, which is a site of the Kumbh Mela, a Hindu festival held every 12 years.
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. 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 Ganga at Sangam or Prayag in Allahbad. It helps create the highly fertile alluvial Yamuna-Ganga Doab region between itself and the Ganga in the Indo-Gangetic plain.