Brahamaputra Basin

Brahamaputra Basin
Executive summary
Brahmaputra basin spreads over 580,000 Sq.km spreads over China (50.5%), India (33.6%),
Bangladesh (8.1%) and Bhutan (7.8%). Although the main river does not flow through the kingdom of
Bhutan, 96 % of Bhutan’s area falls under this Basin. In India, the catchment area spreads over states
of Arunachal Pradesh, Assam, West Bengal, Meghalaya, Nagaland and Sikkim covering 1,94,413 Sq.
km. which is nearly 5.9 % of the total geographical area of the country. The basin lies between
88°11’ to 96°57’ east longitudes and 24°44’ to 30°3’ north latitudes. The upper portion of the basin
(Indian part) lying in Arunachal Pradesh, Nagaland and the some lower portion of the basin falling in
Sikkim is mostly mountain ranges and narrow valleys.
Most portion of the basin lying in Assam and Meghalaya consists of hills, forests and the wide
Brahmaputra valley about 80 km wide on the average. In West Bengal, also, the basin covers of hills
and forests besides the plains in the districts of Koch Behar and Jalpaiguri. Brahmaputra basin in
Indian portion experience winter, summer, monsoon and autum/post-monsoon season.The basin
experience heavy rainfall. The distribution of rainfall in the Brahmaputra basin is different at
different parts of the basin. In southern slopes of Himalayan region falling in this basin experiences
rainfall is over 6000 mm. The minimum and maximum temperature of the basin is 16.16°C and
38.79°C respectively. The higher elevation in the Himalayan ranges experience lower temperatures
and snowfall also.
The catchment area of Brahmaputra River in India, receives a number of tributaries at its north and
south banks. Crop fields, extensive forest cover, tea plantations, grazing land and water logged
swampy areas with a huge network of tributaries are commonly observed components of the
landuse/cover of the Brahmaputra basin. The major part of basin is covered with forest accounting
to 55.48% of the total area. The most predominant soil type found in the basin is the red loamy soil
and alluvial soil. Other important soil types are sandy, loamy, clayey soils, their combinations and
laterite soils. The entire Brahmaputra basin falls in the Eastern Himalayan agro-climatic zone
(Planning commission, 1989). Brahmaputra basin falls in 3 agro-ecological zones. Most of the upper
Brahmaputra sub basin area falls in the ‘Warm perhumid eco-region with brown and red hill soils’.
The Brahmaputra Valley area is dominating by ‘Hot subhumid (moist) to humid (inclusion of
perhumid) eco-regions with alluvial-derived soils’. The lowermost part of the basin is falling in the
‘Warm perhumid eco-region with red and lateritic soils’.
The basin spreads over 22 parliamentary constituencies (2009) comprising 12 of Assam, 4 of West
Bengal, 2 of Arunachal Pradesh, 2 of Meghalaya, 1 of Sikkim and 1 of Nagaland. The total no. of
villages falling in the basin is 20,050 with 33,72,532 no. of households. The total population in this
basin is 1,77,18,190 (Census,2001). The plain region (the Brahmaputra valley) is densely populated in
comparision to the hilly region of this basin. Majority of population is dependent on agriculture and
allied land based activities. Shifting cultivation (slash and burn agriculture) is still the chief means of
livelihood of tribal people. Brahmaputra basin is also rich in mineral resource especially the
Brahmaputra valley.
The Brahmaputra Basin constitutes of two major sub basins “Brahmaputra Upper” and
“Brahmaputra Lower”. The Brahmaputra is further divided into 180 watersheds. The Brahmaputra
Upper and the Lower sub basin comprised of 97 and 83 watersheds respectively. The Brahmaputra
and its tributaries carry more than 30 % of the total water resources potential of the country.
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