Manas River
The Manas River is a transboundary river in the Himalayan foothills between southern Bhutan and India.
It is named after Manasa, the serpent god in Hindu mythology.
It is the largest river system of Bhutan, among its four major river systems; the other three are Amo Chu or Torsa river, Wong Chu or Raidak, Puna Tshang Chu or Sankosh. It is met by three other major streams before it again debouches into India in western Assam. The total length of the river is, flows through Tibet, China for, flows in Bhutan for and then flows through Assam for before it joins the mighty Brahmaputra River at Jogighopa. Another major tributary of the Manas, the Aie river joins it in Assam at Bangpari.
The river valley has two major reserve forest areas, namely the Royal Manas National Park in Bhutan and the contiguous Manas Wildlife Sanctuary encompassing Project Tiger reserve, an elephant reserve and a biosphere reserve, which constitutes a UNESCO World Heritage Site declared in December 1985.
Geography
The Manas River drains of eastern Bhutan and northeast India. It has three major branches: the Drangme Chhu, Mangde Chhu, and Bumthang Chhu that cover most of eastern Bhutan, with the Tongsa and Bumthang valleys also forming part of its catchment. The area drained in Bhutan territory is 18,300 km2 and is bound by the geographical coordinates. A part of the main stem of the river rises in the southern Tibet before entering into India at Bumla pass at the northwestern corner of Arunachal Pradesh.The river flows through Bhutan in a south-west direction between two ranges of the Lower Himalayas in V-shaped gorges and enters into Assam in India into the south-central foot hills of the Himalayas. The valley opens up in the foot hills; marked by the formation of swamps and marshes in the plains. The upper catchment is snow bound while the middle and lower catchment are thickly forested.
The river system as a whole in Bhutan constitutes a length of, the main stem of the river is the Manas or Gongri river, which originates in the West Kameng District of Arunachal Pradesh in India and after flowing in a south westerly direction enters Bhutan near Tashigang. At Tashigong, it is joined by the Kulong Chu, which rises in the northern Himalaya snow ranges of Bhutan. At Tashigong, the bed width of the river is about and river bed elevation is. The river Kulong Chu is formed by two rivers namely, the Tongsa Chu that rises in northern Bhutan near Kula Kangri Peak where the elevation is and the Bumthang River, also called Murchangphy Chu; the combined stream joins the Manas river.
The Lhobrak, or Kuri Chhu, is the main central tributary of the Manas. It is the only river that rises north of the Great Himalayas and it joins the Manas in southern Bhutan; further downstream of the combined stream joining at the Tongsa Chu. Here, the river bed level is. After flowing in a generally south-westerly direction for about in Bhutan, the Aie river enters In India into the Goalpara district of Assam at the village of Agrong. From here, it follows a meandering course for about and outfalls into the Brahmaputra near Jogigopa. Aie River, which rises in the Black mountains at an altitude of about near the village of Bangpari, is about in length. The total length of the Manas measured along its longest tributary the Kur is, out of which about lies in India.
The river valley in the foothills is surrounded by small meadows located among thickly deciduous forested foothills with many rivulets, streams and natural drainage channels related to the river system. In the lower reaches of the river, there are many smooth sandy stretches populated with trees.
The foot hills in Bhutan and India known as Terai and the Duars, which encompass stretch of the foot hills and which are very fertile. Each Duar is named after a stream or hemmed between two streams. Some part of the Duars in Bhutan was under British control. The fertile lands have been developed into tea estates and paddy fields.
Hydrology
The catchment is wholly mountainous, rising within the space of from an elevation of about near the Indian border to the great Himalayan peaks at over along the main Himalayan range bordering Bhutan and Tibet. The huge elevation range and varied climatic conditions are reflected in the great ecological diversity and rich fauna and flora in the river catchment.Climate
The climate is extremely varied, ranging from hot and humid subtropical conditions in the south to cold and dry alpine conditions in the north. From May to October, the southwest monsoon brings heavy rainfall—more than to the southern part—and there is a pronounced dry season in winter. Further north, the rainfall is generally scanty, of the order of, recorded during June–August.The difference between maximum and minimum river flow in monsoon and the dry months is said to be as much as 20 times. The Manas river, the largest north bank tributary of the Brahmaputra, has a recorded maximum discharge of 7,641 cubic metres and contributes 5.48% of the total flows of the Brahmaputra. Its total length up to its confluence with the Brahmaputra is and raises at an altitude of. It has a total catchment area of out of which 85.9% is in hills and plains.
Reserved areas
Out of the large catchment of the river valley, protected or reserved areas have been specifically demarcated, both in Bhutan and India, which are declared national parks or sanctuaries. The two reserved forest and wild life areas cover an area of, which account for about 24% of the total catchment area of of the Manas river valley; brief details are provided.Royal Manas National Park
Royal Manas National Park in southern Bhutan, considered the national heritage of Bhutan, was declared a wildlife sanctuary in 1996 and subsequently raised to the status of a national park in 1993. Covering an area of, the area is forested to the extent of 92% and is a well-preserved Eastern Himalayan ecosystem. The park is bounded on its north by the Black Mountain National Park and the Manas Tiger Reserve on its South in India. Within Bhutan, biological corridors linked with the park are the Thrumshingla National Park in the North, Phibsoo Wildlife Sanctuary in the West, and Khaling Wildlife Sanctuary in the East. As researched so far, the park has a large diversity of tropical grasslands, temperate moist forests, alpine meadows, and scrublands. The various flora and fauna identified in the park are 45 species of mammals, 366 species of birds and 900 species of vascular plants. World Wildlife Fund is actively working on a conservation management plan in association with local wildlife authorities to preserve and protect this national heritage.Some of the important faunal species identified are: the royal Bengal tiger, elephant, gaur, four rare species of golden langur, pygmy hog, hispid hare, greater one-horned rhinoceros and wild Asiatic water buffalo. There are 362 species of birds, out of which four species of hornbills have been recorded. Apart from the Ganges river dolphin other aquan species identified in the river are the deep bodied mahseer, golden mahseer, and chocolate mahseer or katle. Five thousand people live within the park limits in several villages. Tigers, the most revered animal in Bhutan, are estimated to number about 100 and are mostly in this national park and the neighbouring Manas National Park in India
The world's rarest monkeys, the golden langur, which flourish in dense forests, "with its long tail with a tassel at the end, are found both in Bhutan and India, in the two reserved forest sanctuaries. These monkeys found in groups have no hair on their black face but have generous golden ruff on their body. They are found in large numbers – 180 in India and 1200 in Bhutan, as per counts made in 1978 and 1980 respectively.
Manas Wild Life Sanctuary
The Manas Wild Life Sanctuary, located in Assam, is considered as one of "Asia's finest wild life reserves" and is a UNESCO World Heritage Site. It is contiguous to the Bhutan's Royal National Park to its north. It now encompasses a bio reserve, a tiger reserve and also an elephant reserve. The park is well forested and also comprises grass lands and marshes. In 1928, the core of the area was designated a sanctuary and in 1978 it was declared a tiger reserve.Manas River and another tributary of Manas, the Hakua, flow through the sanctuary. A thick mantle of alluvium is the dominant soil of the terrain. Under subtropical climatic conditions, the forest consists of the semi-evergreen forest vegetation with mixed deciduous, littorals and swamps, and interspersed with bamboo and cane. Flooding occurs in large parts of the Bio Reserve.
The park is managed under several conservation management units such as the Core Zone, the Buffer Zone, and the Economic Zone. The park is known for its rare and endangered endemic wildlife such as the tigers, elephants, Assam roofed turtle, hispid hare, golden and capped langurs and pygmy hog, one-horned rhinoceros, Asiatic buffalo, swamp deer, barking deers, leopards, clouded leopards, marbled cats, sloth bears, hoolock gibbons, wild boar, gharials, crocodiles, and river dolphins. Reptiles consist of pythons, common Indian crocodile, common wolf snake, cat snake and many other species. Birds listed include hornbills, common crane, common redshank, Eurasian woodcock, spotted eagles, black-throated diver, little grebe, different types of herons, black ibis, Eurasian sparrowhawk, spot-bellied eagle-owl and several others. The park is home for 22 endangered mammal species. Fish species identified are: katli, jurraha, chenga, telliah, labeo and mahaseer. Conservation measures have been undertaken to prevent poaching, overfishing, encroachments, and many other related issues. These measures are meant to minimise human interference in the fragile core zone, creation of a data base and carry out research on animal and plant populations for better conservation of the ecosystem.
In 1980, the park has been central to the Bodoland agitation of Assam as the Bodos dominating the area took refuge in the sanctuary. Bodos have been demanding autonomy or a separate state of their own on grounds that their lands were incorporated into Assam during the British Raj.
River development options
One of the development projects planned in the past on the Manas River envisaged flood control in the Brahmaputra River and augmentation of flows in the Ganga river system by building a dam on the river at the Indo-Bhutan border. The stored water stored behind the reservoir was proposed to be transferred through a long canal system through the foot hills of the Himalayas crossing 25 major and minor rivers, out of which the major rivers the Sankosh, Raidak, Amo, Kartoya, Teesta, Atrai and Mahananda through North Bengal, and finally out falling into the Kosi River in North Bihar. The project has not proceeded further due to several adverse public opinion and environmental concerns.The proposal mooted in the 1970s to build a dam on the river for multipurpose uses of power, irrigation and flood control in Assam involved a long canal from the Manas reservoir to another reservoir on the Sankosh River. As the canal was passing through the Manas Tiger Reserve, the Ministry of Environment and Forests of Government of India objected to the proposal on the grounds of adverse impact that would occur due to the dam on the Hydrology and ecology of the area. This view was also supported by the World Heritage Committee of UNESCO. The late Prime Minister of India, Rajiv Gandhi upheld the objections and decided to discontinue with the project. It is unlikely to be revived.
The proposal had been mooted as a joint project of India and Bhutan. The pre-feasibility report prepared for this Manas multipurpose project envisaged power generation of 2800 MW. Another cooperation project on the Mandgde Chu, in central Bhutan, tributary of Manas, envisages power generation of 360/600 MW for which Detailed Project Report is under preparation.