Ganges
The Ganges is a trans-boundary river of Asia which flows through India and Bangladesh. The river rises in the western Himalayas in the Indian state of Uttarakhand. It flows south and east through the Gangetic plain of North India, receiving the right-bank tributary, the Yamuna, which also rises in the western Indian Himalayas, and several left-bank tributaries from Nepal that account for the bulk of its flow. In West Bengal, India, a feeder canal taking off from its right bank diverts 50% of its flow southwards, artificially connecting it to the Hooghly River. The Ganges continues into Bangladesh, its name changing to the Padma. It is then joined by the Jamuna, the lower stream of the Brahmaputra, and eventually the Meghna, forming the major estuary of the Ganges Delta, and emptying into the Bay of Bengal. The Ganges–Brahmaputra–Meghna system is the second-largest river on earth by discharge.
The main stem of the Ganges begins at the town of Devprayag, at the confluence of the Alaknanda, which is the source stream in hydrology on account of its greater length, and the Bhagirathi, which is considered the source stream in Hindu mythology.
The Ganges is a lifeline to hundreds of millions of people who live in its basin and depend on it for their daily needs. It has been important historically, with many former provincial or imperial capitals such as Pataliputra, Kannauj, Sonargaon, Dhaka, Bikrampur, Kara, Munger, Kashi, Patna, Hajipur, Kanpur, Delhi, Bhagalpur, Murshidabad, Baharampur, Kampilya, and Kolkata located on its banks or those of its tributaries and connected waterways. The river is home to approximately 140 species of fish, 90 species of amphibians, and also reptiles and mammals, including critically endangered species such as the gharial and South Asian river dolphin. The Ganges is the most sacred river to Hindus. It is worshipped as the goddess Ganga in Hinduism.
The Ganges is threatened by severe pollution. This not only poses a danger to humans but also to many species of animals. The levels of fecal coliform bacteria from human waste in the river near Varanasi are more than 100 times the Indian government's official limit. The Ganga Action Plan, an environmental initiative to clean up the river, has been considered a failure which is variously attributed to corruption, a lack of care from the government, poor technical expertise, poor environmental planning, and a lack of support from religious authorities.
Course
The upper phase of the river Ganges begins at the confluence of the Bhagirathi and Alaknanda rivers in the town of Devprayag in the Garhwal division of the Indian state of Uttarakhand. The Bhagirathi is considered to be the source in Hindu culture and mythology, although the Alaknanda is longer, and therefore, hydrologically the source stream. The headwaters of the Alakananda are formed by snow melt from peaks such as Nanda Devi, Trisul, and Kamet. The Bhagirathi rises at the foot of Gangotri Glacier at Gomukh, at an elevation of and was mythologically referred to as residing in the matted locks of Shiva; symbolically Tapovan, which is a meadow of ethereal beauty at the feet of Mount Shivling, just away.Although many small streams comprise the headwaters of the Ganges, the six longest and their five confluences are considered sacred. The six headstreams are the Alaknanda, Dhauliganga, Nandakini, Pindar, Mandakini and Bhagirathi. Their confluences, known as the Panch Prayag, are all along the Alaknanda. They are, in downstream order, Vishnuprayag, where the Dhauliganga joins the Alaknanda; Nandprayag, where the Nandakini joins; Karnaprayag, where the Pindar joins; Rudraprayag, where the Mandakini joins; and finally, Devprayag, where the Bhagirathi joins the Alaknanda to form the Ganges.
After flowing for through its narrow Himalayan valley, the Ganges emerges from the mountains at Rishikesh, then debouches onto the Gangetic Plain at the pilgrimage town of Haridwar. At Haridwar, a headworks diverts some of its water into the Ganges Canal, which irrigates the Doab region of Uttar Pradesh, whereas the river, whose course has been roughly southwest until this point, now begins to flow southeast through the plains of northern India.
The Ganges river follows a arching course passing through the cities of Bijnor, Kannauj, Farukhabad, and Kanpur. Along the way it is joined by the Ramganga, which contributes an average annual flow of about to the river. The Ganges joins the long River Yamuna at the Triveni Sangam at Prayagraj, a confluence considered holy in Hinduism. At their confluence the Yamuna is larger than the Ganges contributing about 58.5% of the combined flow, with an average flow of.
Now flowing east, the river meets the long Tamsa River, which flows north from the Kaimur Range and contributes an average flow of about. After the Tamsa, the long Gomti River joins, flowing south from the Himalayas. The Gomti contributes an average annual flow of about. Then the long Ghaghara River, also flowing south from the Himalayas of Tibet through Nepal joins. The Ghaghara, with its average annual flow of about, is the largest tributary of the Ganges by discharge. After the Ghaghara confluence, the Ganges is joined from the south by the long Son River, which contributes about. The long Gandaki River, then the long Kosi River, join from the north flowing from Nepal, contributing about and, respectively. The Kosi is the third largest tributary of the Ganges by discharge, after Ghaghara and Yamuna. The Kosi merges into the Ganges near Kursela in Bihar.
Along the way between Prayagraj and Malda, West Bengal, the Ganges river passes the towns of Chunar, Mirzapur, Varanasi, Ghazipur, Ara, Patna, Chapra, Hajipur, Mokama, Begusarai, Munger, Sahibganj, Rajmahal, Bhagalpur, Ballia, Buxar, Simaria, Sultanganj, and Farakka. At Bhagalpur, the river begins to flow south-southeast and at Farakka, it begins its attrition with the branching away of its first distributary, the long Bhāgirathi-Hooghly, which goes on to become the Hooghly River. Just before the border with Bangladesh the Farakka Barrage controls the flow of Ganges, diverting some of the water into a feeder canal linked to the Hooghly for the purpose of keeping it relatively silt-free. The Hooghly River is formed by the confluence of the Bhagirathi River and Ajay River at Katwa, and Hooghly has a number of tributaries of its own. The largest is the Damodar River, which is long, with a drainage basin of. The Hooghly River empties into the Bay of Bengal near Sagar Island. Between Malda and the Bay of Bengal, the Hooghly river passes the towns and cities of Murshidabad, Nabadwip, Kolkata and Howrah.
After entering Bangladesh, the main branch of the Ganges river is known as the Padma. The Padma is joined by the Jamuna River, the largest distributary of the Brahmaputra. Further downstream, the Padma joins the Meghna River, the converged flow of Surma-Meghna River System taking on the Meghna's name as it enters the Meghna Estuary, which empties into the Bay of Bengal. Here it forms the Bengal Fan, the world's largest submarine fan, which alone accounts for 10–20% of the global burial of organic carbon.
The Ganges Delta, formed mainly by the large, sediment-laden flows of the Ganges and Brahmaputra rivers, is the world's largest delta, at about. It stretches along the Bay of Bengal.
Only the Amazon and Congo rivers have a greater average discharge than the combined flow of the Ganges, the Brahmaputra, and the Surma-Meghna river system. In full flood only the Amazon is larger.
Geology
The Indian subcontinent lies atop the Indian tectonic plate, a minor plate within the Indo-Australian Plate. Its defining geological processes commenced seventy-five million years ago, when, as a part of the southern supercontinent Gondwana, it began a northeastwards drift—lasting fifty million years—across the then unformed Indian Ocean. The subcontinent's subsequent collision with the Eurasian Plate and subduction under it, gave rise to the Himalayas, the planet's highest mountain ranges. In the former seabed immediately south of the emerging Himalayas, plate movement created a vast trough, which, having gradually been filled with sediment borne by the Indus and its tributaries and the Ganges and its tributaries, now forms the Indo-Gangetic Plain.The Indo-Gangetic Plain is geologically known as a foredeep or foreland basin.
Hydrology
Major left-bank tributaries include the Gomti River, Ghaghara River, Gandaki River and Kosi River; major right-bank tributaries include the Yamuna River, Son River, Punpun and Damodar. The hydrology of the Ganges River is very complicated, especially in the Ganges Delta region. One result is different ways to determine the river's length, its discharge, and the size of its drainage basin.The name Ganges is used for the river between the confluence of the Bhagirathi and Alaknanda rivers, in the Himalayas, and the first bifurcation of the river, near the Farakka Barrage and the India-Bangladesh Border. The length of the Ganges is frequently said to be slightly over long, about, or. In these cases the river's source is usually assumed to be the source of the Bhagirathi River, Gangotri Glacier at Gomukh and its mouth being the mouth of the Meghna River on the Bay of Bengal. Sometimes the source of the Ganges is considered to be at Haridwar, where its Himalayan headwater streams debouch onto the Gangetic Plain.
In some cases, the length of the Ganges is given by its Hooghly River distributary, which is longer than its main outlet via the Meghna River, resulting in a total length of about, if taken from the source of the Bhagirathi, or, if from Haridwar to the Hooghly's mouth. In other cases the length is said to be about, from the source of the Bhagirathi to the Bangladesh border, where its name changes to Padma.
For similar reasons, sources differ over the size of the river's drainage basin. The basin covers parts of four countries, India, Nepal, China, and Bangladesh; eleven Indian states, Himachal Pradesh, Uttarakhand, Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Bihar, Jharkhand, Punjab, Haryana, Rajasthan, West Bengal, and the Union Territory of Delhi. The Ganges basin, including the delta but not the Brahmaputra or Meghna basins, is about, of which is in India, in Nepal, in Bangladesh, and in China. Sometimes the Ganges and Brahmaputra–Meghna drainage basins are combined for a total of about or. The combined Ganges-Brahmaputra-Meghna basin drainage basin is spread across Bangladesh, Bhutan, India, Nepal, and China.
The Ganges basin ranges from the Himalaya and the Transhimalaya in the north, to the northern slopes of the Vindhya range in the south, from the eastern slopes of the Aravalli in the west to the Chota Nagpur plateau and the Sunderbans delta in the east. A significant portion of the discharge from the Ganges comes from the Himalayan mountain system. Within the Himalaya, the Ganges basin spreads almost 1,200 km from the Yamuna-Satluj divide along the Simla ridge forming the boundary with the Indus basin in the west to the Singalila Ridge along the Nepal-Sikkim border forming the boundary with the Brahmaputra basin in the east. This section of the Himalaya contains 9 of the 14 highest peaks in the world over 8,000m in height, including Mount Everest which is the high point of the Ganges basin. The other peaks over 8,000m in the basin are Kangchenjunga, Lhotse, Makalu, Cho Oyu, Dhaulagiri, Manaslu, Annapurna and Shishapangma. The Himalayan portion of the basin includes the south-eastern portion of the state of Himachal Pradesh, the entire state of Uttarakhand, the entire country of Nepal and the extreme north-western portion of the state of West Bengal.
The discharge of the Ganges also differs by source. Frequently, discharge is described for the mouth of the Meghna River, thus combining the Ganges with the Brahmaputra and Meghna. This results in a total average annual discharge of about, or. In other cases the average annual discharges of the Ganges, Brahmaputra, and Meghna are given separately, at about for the Ganges, about for the Brahmaputra, and about for the Meghna.
The maximum peak discharge of the Ganges, as recorded at Hardinge Bridge in Bangladesh, exceeded. The minimum recorded at the same place was about, in 1997.
The hydrologic cycle in the Ganges basin is governed by the Southwest Monsoon. About 84% of the total rainfall occurs in the monsoon from June to September. Consequently, streamflow in the Ganges is highly seasonal. The average dry season to monsoon discharge ratio is about 1:6, as measured at Hardinge Bridge. This strong seasonal variation underlies many problems of land and water resource development in the region. The seasonality of flow is so acute it can cause both drought and floods. Bangladesh, in particular, frequently experiences drought during the dry season and regularly suffers extreme floods during the monsoon.
In the Ganges Delta, many large rivers come together, both merging and bifurcating in a complicated network of channels. The two largest rivers, the Ganges and Brahmaputra, both split into distributary channels, the largest of which merge with other large rivers before themselves joining the Bay of Bengal. But this current channel pattern was not always the case. Over time the rivers in Ganges Delta have often changed course, sometimes altering the network of channels in significant ways.
Before the late 12th century the Bhagirathi-Hooghly distributary was the main channel of the Ganges and the Padma was only a minor spill-channel. The main flow of the river reached the sea not via the modern Hooghly River but rather by the Adi Ganga. Between the 12th and 16th centuries, the Bhagirathi-Hooghly and Padma channels were more or less equally significant. After the 16th century, the Padma grew to become the main channel of the Ganges. It is thought that the Bhagirathi-Hooghly became increasingly choked with silt, causing the main flow of the Ganges to shift to the southeast and the Padma River. By the end of the 18th century, the Padma had become the main distributary of the Ganges. One result of this shift to the Padma was that the Ganges now joined the Meghna and Brahmaputra rivers before emptying into the Bay of Bengal. The present confluence of the Ganges and Meghna was formed very recently, about 150 years ago.
Also near the end of the 18th century, the course of the lower Brahmaputra changed dramatically, significantly altering its relationship with the Ganges. In 1787 there was a great flood on the Teesta River, which at the time was a tributary of the Ganges-Padma River. The flood of 1787 caused the Teesta to undergo a sudden change course, an avulsion, shifting east to join the Brahmaputra and causing the Brahmaputra to shift its course south, cutting a new channel. This new main channel of the Brahmaputra is called the Jamuna River. It flows south to join the Ganges-Padma. During ancient times, the main flow of the Brahmaputra was more easterly, passing by the city of Mymensingh and joining the Meghna River. Today this channel is a small distributary but retains the name Brahmaputra, sometimes Old Brahmaputra. The site of the old Brahmaputra-Meghna confluence, in the locality of Langalbandh, is still considered sacred by Hindus. Near the confluence is a major early historic site called Wari-Bateshwar.
In the rainy season of 1809, the lower channel of the Bhagirathi, leading to Kolkata, had been entirely shut; but in the following year it opened again and was nearly of the same size as the upper channel but both however suffered a considerable diminution, owing probably to the new communication opened below the Jalanggi on the upper channel.