koshi (sorrow of bihar)

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Koshi River
River
Countries China, Nepal, India
State Bihar

Cities Biratnagar, Purnia, Katihar

The Kosi River -- called Koshi in Nepal (Nepali: कोशी नदी) as well as Saptakoshi for its seven Himalayan tributaries -- is a transboundary river between Nepal and India, one of the largest tributaries of the Ganges.

The river, along with its tributaries, drains a total area of 69,300 km2 (26,800 sq mi) up to its confluence with the Ganges in India (29,400 km2/11,400 sq mi in China, 30,700 km2/11,900 sq mi in Nepal and 9,200 km2/3,600 sq mi in India). The watershed also includes part of Tibet, including the Mount Everest region, and the eastern third of Nepal.

The river basin is surrounded by the ridges separating it from the Yarlung Zangbo River in the north, the Gandaki in the west, the Mahananda in the east, and by the Ganges in the south. The river is joined by major tributaries in the Mahabharat Range approximately 48 km (30 mi) north of the Indo-Nepal border. Below the outermost foothills (Siwaliks) the river has built up a megafan some 15,000 sq. km in extent, breaking into more than twelve distinct channels with shifting courses due to flooding.[1][2] Kamlā, Bāghmati (Kareh) and Budhi Gandak are major tributaries of Koshi in India, besides minor tributaries like Bhutahi Balān.[3][4] Over the last 250 years, the Kosi River has shifted its course over 120 kilometres (75 mi) from east to west.[5] and the unstable nature of the river is attributed to the heavy silt which it carries during the monsoon season. Flooding in India has extreme effects. India is second in the world after Bangladesh in deaths due to flooding, accounting for one fifth of global flooding deaths. The Kosi River (The Sorrow of Bihar) is one of two major tributaries, the other river being Gandak, draining the plains of north Bihar, the most flood-prone area of India[6]
Kanchenjunga. It has seven major tributaries: the Sun Koshi, the Tama Koshi or Tamba Koshi, the Dudh Koshi, the Indravati, the Likhu River, the Arun and the Tamur. The Dudh Koshi joins the Sun Koshi at the Nepalese village of Harkapur. At Triveni Sun the Koshi is joined by the Arun and the Tamar, after which the river is called the Sapta Koshi. At Barāhkṣetra in Nepal, it descends from the mountains and it is then called simply the Koshi. These tributaries encircle Mt Everest from all sides and are fed by the world's highest glaciers. Further down the Triveni, the river cuts a deep gorge across the lesser Himalayan range of Mahabharat Lekh in a length of 10 km (6.2 mi) and debouches into the plains near Chatra. After flowing for another 58 km (36 mi), it enters the north Bihar plains near Bhimnagar and after another 260 km (160 mi), flows into the Ganges near Kursela(1). The river travels a distance of 729 km (453 mi) from its source to the confluence with the Ganges.

The Kosi river fan located in the northern part of India (in northeast Bihar and eastern Mithila) is one of the largest alluvial cones built by any river in the world. This 180 km (110 mi)-long and 150 km (93 mi)-wide alluvial cone shows evidence of lateral channel shifting exceeding 120 km (75 mi) during the past 250 years through more than 12 distinct channels. The river, which used to flow near Purnea in the 18th century, now flows west of Saharsa (1). The Kosi alluvial cone and its adjoining area have been studied in detail by remote sensing techniques. The data have been integrated with the available geological and geophysical information to decipher the causes responsible for the lateral shift of such a high-magnitude fan. A satellite image shows the old palaeo-channels of the Koshi river with its former (before 1731) confluence with the Mahananda River north of Lava.[7]