About
Brahmaputra delta |
The
Ganges Delta (also known as the Ganges–Brahmaputra Delta, the
Sunderbans Delta, or the Bengal Delta) is a river delta in the
South Asia region of Bengal, where the Ganges and Brahmaputra
rivers discharge into the Bay of Bengal consisting of
Bangladesh and the state of West Bengal, India. It is, with a
surface area of some 100.000 km2, the world's largest Delta.
About two-thirds of the delta is in Bangladesh, the rest
comprises the state of West Bengal, India. It is also one of
the most fertile regions in the world, thus earning the
nickname the Green Delta. It is the world's largest delta, and
empties into the Bay of Bengal. The delta extends from the
Hooghly River on the west to the Meghna River on the east. It
is about 350 km (220 mi) across at the Bay of Bengal. Kolkata
and Haldia in India and Mongla and Chittagong in Bangladesh
are the principal seaports the delta.
A number of large rivers flow through the Ganges Delta,
including the Padma (main distributary of the Ganges) and the
Jamuna (main distributary of the Brahmaputra), which combine
and then join the Meghna before entering the sea.The Ganges
Delta is the floodplain of three great rivers: the Ganges, the
Brahmaputra and the Megna. Together, these three rivers drain
a catchment of about 1.72 million km2, at the southern side of
he Himalaya.
The Ganges Delta is among the most fertile regions in the
world. Along the coast, the width of the delta is about 350
km. The distance from the convergence of the Brahmaputra and
the Ganges to the coast is about 250 km. Downstream the
confluence, the river is named Padma.The Meghna joins about
halfway the Padma. With some 130 million inhabitants, the
Ganges delta belongs to the most densely populated areas in
the world. |
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General characteristics of Brahmaputra delta |
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Continent: Asia
• Average rainfall (mm/y): 1474
• Basin of deposition: Bay of Bengal
• Delta area (km2): 105641
• Number of river mouths: 8
• Spring Tide (m): 3.63
• Major Cities: Dhaka, Kolkata
• Basin area (10^3 km2): 1664.7
• River length (km): 3902
• Maximum discharge (m3/s): 80984
• Minimum discharge (m3/s): 6041
• Maximum rainfall (mm/y): 2269
• Minimum rainfall (mm/y): 341
• Annual average discharge (m3/s): 29692 |
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Flora and fauna |
Three
terrestrial ecoregions cover the delta. The Lower Gangetic
plains moist deciduous forests ecoregion covers most of the
delta region, although the forests have mostly been cleared for
agriculture and only small enclaves remain. Thick stands of tall
grass, known as canebrakes, grow in wetter areas. The Sundarbans
freshwater swamp forests ecoregion lies closer to the Bay of
Bengal; this ecoregion is flooded with a little brackish water
during the dry season, and fresh water during the monsoon
season. These forests, too, have been almost completely
converted to intensive agriculture, with only 130 square
kilometres (50 sq mi) of the ecoregion's 14,600 square
kilometres (5,600 sq mi) protected. Where the delta meets the
Bay of Bengal, Sundarbans mangroves form the world's largest
mangrove ecoregion, covering an area of 20,400 square kilometres
(7,900 sq mi) in a chain of 54 islands. They derive their name
from the major mangrove species, Heritiera fomes, which are
known locally as sundri or sundari.
Animals in the delta include the Indian Python (Python molurus),
Clouded Leopard (Neofelis nebulosa), Indian Elephant (Elephas
maximus indicus) and crocodiles, which live in the Sundarbans.
About 1,020 endangered Bengal tigers (Panthera tigris tigris)
are believed to inhabit the Sundarbans.Trees found in the delta
include garjan, sundari, bamboo, mangrove date palm and mangrove
palm.
It is estimated that 30,000 chital are in the Sundarbans part of
the delta. Birds found in the delta include eagles, woodpeckers,
kingfishers, the shalik (Acridotheres tristis), the Swamp
Francolin (Francolinus gularis), and the doel (Copsychus
saularis). Two species of dolphin can be found in the delta: the
Irrawaddy Dolphin (Orcaella brevirostris) and the Ganges River
Dolphin (Platanista gangetica gangetica). The Irrawaddy Dolphin
is an oceanic dolphin that enters the delta from the Bay of
Bengal. The Ganges River Dolphin is a true river dolphin, but is
extremely rare and considered endangered. |
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Shape and composition |
The Ganges delta has the shape of a triangle, and is
considered to be an "arcuate" delta (arc-shaped). It
covers more than 105,000 km2 (41,000 sq mi), and although
the delta lies mostly in Bangladesh and India, rivers from
Bhutan, China, India, and Nepal drain into it from the
north. About two-thirds of the delta is in Bangladesh.
Most of the delta is comprised of alluvial soils made up
by small sediment particles that finally settle down as
river currents slow down in the estuary. Rivers carry
these fine particles with them, even from their sources at
glaciers as Fluvio-glacial. Red and red-yellow laterite
soils are found as one heads beyond east. The soil has
large amounts of minerals and nutrients, which is good for
agriculture.
It is composed of a labyrinth of channels, swamps, lakes,
and flood plain sediments (Chars). The Ganges Delta is
separated into two parts: eastern (active), and the
western (less active). |
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Geology |
The
Ganges Delta lies at the junction of three tectonic plates: the
Indian Plate, the Eurasian Plate, and the Burma Plate. Huge
sediment supply since the Himalayan collision made 400 km
progragation of the shelf edge since Eocene. The edge of the
paleoshelf in Eocene runs from Calcutta to the edge of the
Shilong Plateau. The edge of the paleoshelf marks the transition
from the thick continental crust in the northwest to the thin
continental and oceanic crust in the southeast. The sediment
thickness southeast of the edge of the paleoshelf beneath the
Ganges Delta can exceed 16 km. |
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Infrastructure |
As
there is a maze of many river branches, the area is difficult to
pass. Most islands are only linked with the mainland by simple
wooden ferryboats. Bridges are rare. Some islands are not yet
connected to the electric grid, so island residents tend to use
solar cells for a bit of electric supply. |
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Climate |
Mostly the Ganges Delta lies in the tropical wet climate zone,
and receives between 1,500 to 2,000 mm (59 to 79 in) of
rainfall every year in the western part, and 2,000 to 3,000 mm
(79 to 120 in) in the eastern part. |
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Agriculture and fishing |
About
two-thirds of the Bangladesh people work in agriculture, and
grow crops on the fertile floodplains of the delta. The major
crops that are grown in the Ganges Delta are tea, rice, and
jute. Fishing is also an important activity in the delta region,
with fish being a major source of food for many of the people in
the area.
In recent years, scientists have been helping the poor people of
the delta to improve fish farming methods. By turning unused
ponds into feasible fish farms, and improving methods of raising
fish in existing ponds, many people can now earn a living
raising and selling fish. Using new systems, fish production in
existing ponds has increased 800%. Shrimp and salmon are farmed
in containers or cages that are submerged in open water—most of
these fish are exported.There are also other crops grown along
the Ganges River. |
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Ganges Brahmaputra River Basin |
The Ganges and Brahmaputra rivers both have their source in
the Himalayas where glacier melt water is an important
source for the headwaters of the river. The whole drainage
basin is just over 1.6 million km2 (0.6 million miles2). The
Brahmaputra river originates in eastern Tibet where as the
Ganges river’s source is in the West by the Tibet/India
border and flows south east across India to join the
Brahmaputra river in Bangladesh. From here the Ganges-Brahmaputra
River flows to the Bay of Bengal where it forms the Ganges
Delta. This delta is one of the largest in the world and has
the highest population density of any delta.
The world’s higher population density is supported by the
Ganges and Brahmaputra rivers making them important to the
survival of millions of people. |
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Population |
Between 125 and 143 million people live on the delta, despite
risks from floods caused by monsoons, heavy runoff from the
melting snows of the Himalayas, and tropical cyclones. A large
part of the nation of Bangladesh lies in the Ganges Delta, and a
lot of country's people depend on the delta for survival.
It is believed that upwards of 300 million people are supported
by the Ganges Delta, and about 400 million people live in the
Ganges River Basin, making it the most populous river basin in
the world. Most of the Ganges Delta has a population density of
more than 200 people per km2 (520 people per square mile),
making it one of the most densely populated regions in the
world. |
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