The Kosi River is a transboundary river between Nepal and India. This is one of the largest tributaries of the Ganga, which. traverses a distance of 729 kilometres or 452 miles from its source to the confluence with the Ganga. The Kosi flows to the south and west of Kanchenjunga with an average water flow of 2,564 cubic metres per second. The tributaries of the Kosi encircle Mt. Everest from all sides.
The Kosi is fed by the highest. glaciers of the world.
In the Mahabharata, it has been referred to as Kausiki river. The sage Vishwamitra is also known as Kausik, since he was a descendant of sage Kusika and was called Kausika in Rig Veda. He is said to have attained enlightenment on the banks of the Kosi. Therefore the river is called Kausiki. According to the epic, seven rivers join together to form the Saptakosi river which is called the Kosi. The seven streams that form it are Sun Kosi, Tama Kosi or Tamba Kosi, Dudh Kosi, Likhu, Indravati, Arun and Tamore or Tamar.
The Kosi, up to its confluence with the Ganga, drains a total area of 69,300 square kilometres along with its tributaries—30,700 square kilometres in. Nepal, 29,400 square kilometres in Tibet, a part of China and 9,200 square kilometres in India, which includes the Mt. Everest region as well as the eastern one-third of Nepal.
The Sapta Kosi river is an important tributary of Kosi. It is the main water source of the Kosi river, and one of the principal sources of water for the Kosi river basin. It originates in the Tibetan mountains at an altitude of 5,646 metres or 18,523 feet.
The Dudh Kosi, along with its tributaries, joins the Sun Kosi at the village Harkapur in Nepal. The Dudh Kosi, meaning the Milky River, is so called the water. of the river is extremely white, like milk. It originates just east of Gokyo Lakes and flows south to. Namche Bazaar where it meets the Bhote Kosi River. Continuing south, the Dudh Kosi exits. Sagarmatha National Park and passes to the west of Lukla. The Lamding Khola River joins the Dudh Kosi to the southwest of Surkya and continues its southerly course to Harkapur, where it joins the Sun Kosi.
The Arun is another tributary of the Kosi river, which flows through Nepal, Tibet and China. It contributes a huge amount of water to the Ganga. This tributary of the Kosi demarcat es the ancient boundary of Khambuwan and Limbuwan regions. The river is also important in the folklore of Kiranti people of eastern Nepal.
The Sun Kosi further confluences with Arun and Tamar at Triveni after which it is called Sapta Kosi. Further down the Triveni, the river cuts a deep gorge. across the lesser Himalayan range of Mahabharata Lekh in a length of ten kilometres. The. river descends from the hills int o the plains near Chatra at Barah Kshetra in Nepal where it is. known as Kosi. Thereafter flowing for another fifty-eight kilometres, it enters the plains of northern Bihar near Bhimnagar. The Kosi traverses 260 kilometres in Bihar. The main stream of the river flows into the Ganga near Kursela.
There are three major tributaries of the Kosi in addition to its. seven headwaters. Kamla, Baghmati or Kareh and Budhi Gandak are other rivers that merge into the Kosi in India. Certain rivulets also join the Kosi in Nepal and India, and Bhutahi Balan is the chief among its minor tributaries. Budhi Gandak is an important river, which originates from West Champaran near Ramanagar and Bagaha. It passes through East Champaran, Mujaffarpur, Samastipur, Khagaria districts of Bihar. The river finally flows into the Ganga at Manasi near Khagaria.
The Kosi is the lifeline of the Mithila region, which spreads across more than half of Bihar and the adjoining terai belt of. Nepal. It is also one of the most dynamic rivers in Asian region. The river changes its course constantly, and in the last three hundred years has shifted over hundred miles from east to west. The river which used to flow near Purnea in the eighteenth century now flows west of Saharsa. The unstable nature of the river is attributed to the heavy silt which it carries during the monsoon season.
The uncertain propensity of avulsion is similar in many tributaries of the Kosi. The basin of river Kosi is surrounded by the ridges separating it from the Brahmaputra in the north, the Gandak in the west, Mahananda in the east and the Ganga in the south. The Kosi forms large alluvial cones, 180 kilometres long and 150 kilometres wide, which is the largest cone built. by any river in the world. The scientific study of its alluvial cone and its adjoining area decipher the causes responsible for the. lateral shifting. The former confluence of the Kosi with the Mahananda river is reflected by this study.
There are two famous wildlife reserves in the river basin of the Kosi. The Sagarmatha National Park, located in eastern Nepal, containing parts of the Himalayas and the southern half of Mount Everest and the Kosi Tappu Wildlife Reserve situated on the floodplains of the Sapta. Kosi River in Eastern Nepal. Sagarmatha National park covers an area of 1,148 square kilometres and ranges in elevation from its lowest point of 2,845 metres at Jorsalle to 8,848 metres at the summit of Mount Everest. The upper watershed of the Dudh Kosi river basin system lies in the park. Kosi Tappu Wildlife reserve is a wetland. situated in the flood plains of the Saptakosi river in the eastern terai region of Nepal. It spreads across 175 square kilometres and is one of the outstanding bird reserves in the Indo-Gangetic grasslands.
Various types of plants and animals are found in these parks, including a number of rare species like musk deer, wild yak , snow leopard, Himalayan black bear and red panda, etc. Besides them there are many other animals such as Himalayan thar s, deer, langur and monkeys, hares, mountain foxes, martens, hog deer, spotted deer, wild bo ar, blue bull, rock python and. Himalayan wolves. The presence of these creatures depends on the altitude.
These forests provide habitat to more than 80 fish species, around 441 species of birds, 30 shore birds, 114 water birds, 20 ducks and 2 ibises, etc. The major bird species of the region includes danphe, blood pheasant, red-billed chough, and yellow-billed chough. The Gangetic river dolphin, a fresh water dolphin, also known as susu, an endangered species is found in this region. The Kosi region is an extremely importan t place for migratory birds.
The forested area grows various. types of flora and fauna. The birch, juniper, blue pines, firs, bamboo and rhododendron grow in the lower forested zone. Vegetation is found to be dwarf or shrubs above this zone. As the altitude increases, plant life is restricted to lichens and mosse s. Plants cease to grow at about 5,750 metres, in the permanent. snowline in the Himalayas.
The Kosi is known as the sorro w of Bihar, since it causes frequent floods. The milky river has caused widespread human suffering in the past due to flooding and frequent changes I n its course. In order to control floods, the Kosi Barrage has been designed for a peak flood of 27,014 cumecs or 950,000 cusecs. Kosi has an average water flow (discharge) of 1,564 cumecs or 55,000 cusecs. During peak floods, it increases to about eighteen times over. The highest flood recorded in. living memory in the river is reported to be 24,200 cumecs or 850,000 cusecs on 24 August 1954. India stands second in the world after Bangladesh in the number of deaths caused by flood; Bangladesh alone. accounts for one-fifth of total deaths due to flooding globally.
Kaushal Kishore is the author of The Holy Ganga