Saturday, February 9, 2008

Brahmaputra River



Brahmaputra River Initial Resources Inventory

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Last Updated:2005-7-19 10:37:22

The AIRC has been asked by the Tibetan Bureau of Water Resources to develop a paper on the Brahmaputra River. The report will cover current ecological conditions, water resources, and planned activities for the area. It will also explore Indian perceptions towards Chinese management of its portion of the river.

CONTENTS:

Regional Summary, Land Use, Politics and Culture, Hydropower and Infrastructure Development, Trade and Economics, Hydrology, Habitat and Ecosystems

Regional Summary

The Brahmaputra River flows 2,900 km from its source in the Kailas range of the Himilayas to its massive delta and the Bay of Bengal in Bangladesh. It flows through China, India, and Bangladesh, but its watershed includes Nepal, Bhutan, and Burma as well.The river drops steeply from high on the Tibetan Plateau through the world"s deepest valley (5,075m) into northeast India where the river eventually merges with the Ganges and Meghna rivers to form the largest river delta in the world (60,000km2).The Brahmaputra basin covers 651,334 km2 (WRI), 58% of which lies in India and 20% in China.

The river is defined by its diverse terrain subject to regular earthquakes, natural disasters, and other changing conditions.

Land Use (WRI)

29% of the basin is actively used as cropland, almost half of which is irrigated. Only 3% of the basin is developed as urban land and 2% is considered barren. 19% is covered by forest, 16% by shrub, 29% by grassland, 21% by wetland, and 11% is considered eroded land.

Politics and Culture

The river"s three names, the Brahmaputra (India), Yarlung Zangbo (Tibet), and Jamuna (Bangladesh), reflect the complicited fabric of ethnic groups and international communities living along its banks. The Brahmaputra flows through some of the most heavily disputed and unstable areas in South Asia. China and India currently dispute 83,000 km2 within the basin. Much of the boundary between the two countries is based on administrative units that do not shift with the rivers as they change course or level over time. Alluvial or "char" land that is exposed as a river shifts often leads to dispute, as the land is highly valued for agriculture(CIA World Factbook, 1998; IBRU, 1999). (Click here for more on India-China relations).


In northeast India, more than 6 seperatist and rebel groups are active.(Click here for map of rebel activity). Recent riots contributed to the deaths of hundreds of Burmese and other immigrants and led to demonstrations. The northeast is one of the poorest regions in India. Currently population density, on average, is 174 people per square mile, but this population is concentrated in 14 large cities in the region. Urban areas are growing at 5% a year (WRI). The Brahmaputra basin has seen a surge in millions of people immigrating to the area from Bangladesh and West Bengal. Increasing densities have led to competition for jobs and land. In 1999, 500 people died from ethnic violence in Northeast India (US Commission on Refugees). In the mid 1960s the Indian government relocated 3,000 ethnic Chakmas to Arunachal Pradesh from what is now Bangladesh after construction of a large dam. The influx has caused conflict in this state.

In the ancient Indian tradition, two rivers are known to originate from Manasarovar Lake, in Mt. Kailas; one flowing to the east is called Brahmaputra and the other flowing to the west was called Shatadru, a tributary of the Sarasvati (joining the latter at Shatrana, Punjab) in Rigvedic times. Both these major rivers, Brahmaputra and Sarasvati are related to the God of creation, Brahma. The lower portion of the river is sacred to Hindus.

Hydropower and Infrastructure Development

In 1980, the Indian government established the Brahmaputra Board as a statutory body under the Ministry of Water Resources to plan for and implement projects to harness the river for hydropower, flood control, and economic development.The Board has identified 34 "Drainage Development schemes" that include hydropower dams, embankment reinforcement, and other multipurpose projects. These projects are included in the Board"s Master Plan, approved by the Indian government in 1997.Currently there are no large dams on the Brahmaputra. (Click here for project descriptions).

It is estimated that the Brahmaputra"s power potential could provide about 48000 MW. This constitutes as much as 30 per cent of the total hydropower reserves of India, but less than even 3 per cent of this has yet to be harnessed.

Trade and Economics

The river is navigable for large crafts 1,290 km upstream from the Bay of Bengal to Dibrugarh, India.The lower portions of the river are used heavily to transport agricultural products. A major earthquake in 1950 (magnitude 8.7 on the Richter scale) and disputes over water rights impeded further access upstream. The Brahmaputra Valley in Assam has marshy jungle, teak forest, and commercial fisheries; rice, jute, tea, and sugarcane are grown there as well. In Tibet, the river forms and important east-west transportation route.

There currently exisits a rapidly growing trade relationship between India and China. Both Indian exports and imports through China have grown tremendously since 1999.

Hydrology

The Brahmaputra"s flows fluctuate drastically between high and low flows. High flows, peaking in mid June, can run at 72,460 m3/s (1962 flood). The mean annual flood discharge of the river is 48,160 m3/sec at Pandu (India). Its minimum recorded dry-season flow was only 3,280 m3/s in 1960.

The average annual rainfall in the basin is 230 cm with a marked variability in distribution over the watershed. Rainfall in the lower Himalayan region amounts to more than 500cm per year with higher elevations getting progressively lesser amounts. The rainfall intensity occassionally records exceedingly high rates causing flash floods, landslides, debris flow and erosion.

The rains begin in May or early June, and the wet season lasts to October. From June to September, the rains occur nearly daily. A period of fluctuating high flow follows, usually with peaks in July and September. The last peak is followed by a long recession into December and January.

During the rainy season there, the river often floods to 8 km wide, rising 9-12 m and depositing sediment carried down from the mountains.

Habitat and Ecosystems

Over 73% of the Brahmaputra River watershed"s originial forest is gone. The remaining forests are disappearing at 10% per year. Currently only 4% of the land is in protected areas. The area supports 4 endemic bird habitats and one RAMSAR-listed wetland.126 fish species also call the Brahmaputra basin home (WRI).

(The following is excerted from http://www.worldwildlife.org/wildworld/profiles/terrestrial/im/indo_ref.html) - World Wildlife Fund)

The ecoregion covering the Brahmaputra River in northeast India harbors India"s largest elephant population (Rodgers and Panwar 1988), the world"s largest population of the greater one-horned rhinoceros, tigers (Panthera tigris), and wild water buffalo (Bubalus arnee) (WII 1997). The ecoregion overlaps with a high-priority (Level I) ecosystem that extends north to include the subtropical and temperate forests of the Himalayan midhills (Wikramanayake et al. 1999).

The known mammal fauna consists of 122 species, including 2 near-endemic species. Of these, the pygmy hog and the hispid hare are confined to the grassland habitats.

At present, twelve protected areas cover about 2,500 km2 of intact habitat, or 5 percent of the ecoregion. Of these, Manas, Dibru-Saikowa, Kaziranga, and Mehao are the larger and more important reserves. Mehao extends over two other ecoregions and is only partially within this ecoregion. Kaziranga has the world"s largest population of the greater one-horned rhinoceros, estimated at 1,100 individuals (Foose and van Strien 1997). Because of the large number of wide-ranging large vertebrates in this ecoregion, additional protection is urgently needed. Specifically, habitat connectivity should be provided within the Buxa-Manas complex and the Barail-Intanki-Kaziranga complex to allow elephants to disperse and migrate (Rodgers and Panwar 1988).

The ecoregion represents the swath of semi-evergreen forests along the upper Brahmaputra River plains. Most of the ecoregion lies within the eastern Indian state of Assam, but small sections extend into the neighboring states of Arunachal Pradesh and Nagaland and also into the southern lowlands of Bhutan.

The wide Brahmaputra River is also a biogeographic barrier for several species. For instance, the golden langur (Semnopithecus geei), hispid hare (Caprolagus hispidus), and pygmy hog (Sus salvanius) are limited to the north bank of the river, whereas the hoolock gibbon (Hylobates hoolock) and stump-tailed macaque (Macaca arctoides) are limited to the south bank (Rodgers and Panwar 1988).

The June to September southwest monsoon is funneled through the Gangetic River plains, flanked by the Himalayas to the north and the Mizo Hills to the south, deluging the ecoregion with 1,500-3,000 mm of rainfall, depending on the topographic variation. The substrate consists of deep alluvial deposits, washed down over the centuries by the Brahmaputra and other rivers such as the Manas and Subansiri, which drain southern slopes of the Eastern Himalaya. The ecoregion"s vegetation therefore is thus influenced by the rich alluvial soils and the monsoon rains.

Champion and Seth (1968) recognize the following forest types in this ecoregion: Assam Valley semi-evergreen forest, Assam alluvial plains semi-evergreen forest, eastern submontane semi-evergreen forest, sub-Himalayan light alluvial semi-evergreen forest, eastern alluvial secondary semi-evergreen forest, sub-Himalayan secondary wet mixed forest, and Cachar semi-evergreen forest. But most of the ecoregion"s original semi-evergreen forests have been converted to grasslands by centuries of fire and other human influences. Only small patches of forests now remain, scattered along the Indo-Bhutan border and along the border of Assam and Meghalaya. Many of these forest patches are confined to protected areas.

According to Champion and Seth (1968), the typical evergreen tree species in these forests are Syzygium, Cinnamomum, Artocarpus, and Magnoliacea, and the common deciduous species include Terminalia myriocarpa, Terminalia citrina, Terminalia tomentosa, Tetrameles spp., and Stereospermum spp. Shorea robusta is present in disturbed habitats, especially in areas that have been subjected to fire, and represents a sub-climax community. Other Dipterocarpus species are considered to be indicative of a forest in retrogression from the tropical evergreen or as a preclimax stage. Typically, the canopy trees are 20-30 m high.

The understory is of Lauraceae (mostly Phoebe spp., Machilus spp., and Actinodaphne spp.), Anonaceae (Polyalthia spp.), Meliaceae (Aphanamixis spp.), Mesua ferrea, Tetrameles spp., Stereospermum spp., and species of Meliaceae, Anacardiaceae, Myristicaceae, Lauraceae, and Magnoliaceae, with several bamboos such as Bambusa arundinaria, Dendrocalamus hamilitonii, and Melocanna bambusoides (Champion and Seth 1968; Puri et al. 1989).

The riparian areas along the Brahmaputra River that have been cleared are characterized by wet grasslands with similar communities and dynamics as described under the Terai-Duar Savanna and Grasslands [IM0701] description. Species such as the hispid hare and pygmy hog are found in these grasslands, especially in the soft soils and muddy areas along the river courses.

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1 comment:

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