Brahmaputra River ecosystem
The Brahmaputra River ecosystem, spanning Tibet, India, and Bangladesh, is a complex and vital system characterized by its rich biodiversity and significant socio-economic roles. Originating from the Tibetan Plateau, the river flows approximately 1,800 miles before merging with the Ganges, eventually reaching the Bay of Bengal. It is known for its braided structure, with numerous channels and shifting sediment islands, shaped by annual flooding and monsoon rains. This flooding supports floodplain lakes that foster diverse fish populations, although increased irrigation and flood control measures have led to challenges such as weed infestations and reduced productivity of these natural habitats.
The river is home to several endangered species, including the Gangetic dolphin and the Indian gharial, both of which face threats from habitat loss, pollution, and fishing practices. The ecosystem also encounters significant pressures from human activities, as communities rely on the river for irrigation and hydropower, which can lead to political tensions among the countries that share its waters. Additionally, climate change poses an increasing risk of catastrophic flooding and altered water availability, further complicating the balance between ecological preservation and human needs. Understanding the Brahmaputra River ecosystem is crucial for addressing these environmental and social challenges.
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Brahmaputra River ecosystem
- Category: Inland Aquatic Biomes.
- Geographic Location: South Asia.
- Summary: The Brahmaputra River flows through Tibet, India, and Bangladesh; the flood-prone river is home to endangered species and is the focus of international wrangling over electricity generation and irrigation.
The Brahmaputra River originates on the Tibetan Plateau on the northern slope of the Himalayan mountains, where it is primarily fed by melting glaciers and snow from the high Himalayas. The river flows along the plateau, then breaks down through gorges in the Himalayas to the southern slope, leaving Tibet (China) for India, where it continues its journey toward Bangladesh. The waters of the Brahmaputra there become the Jamuna River, finally blending with the Padma before it meets the Ganges; this flow ends its roughly 1,800-mile (2,900-kilometer) journey into the Bay of Bengal.
The Brahmaputra River is a vital resource for plant and animal habitat, human irrigation and navigation, but annual floods can cause havoc for every type of community living near its flood-prone banks. As a river that runs through three countries, the Brahmaputra has also become a source of political tension as areas upstream plan to use the river in ways that may diminish its flow to dependent zones downstream.
The Brahmaputra is an example of a braided river, having many small channels that are separated by temporary and shifting islands that are essentially sediment bars. Such river types occur in systems that have either high slopes or have high loads of sediment carried by their waters. The Brahmaputra River meets both these conditions as it transports sediments from the Himalayas to the valleys and plains below. In some stretches, the river forks into separate major channels that flow more than 60 miles (100 kilometers) before rejoining. The course of the Brahmaputra changes with these shifting channels and sediment bars, which are influenced by annual floods.
Flooding can result in drastic changes of overall river width, spreading the Brahmaputra out to as much as 12 miles (19 kilometers) wide. Monsoon rains and annual river flooding serve to maintain a system of floodplain lakes; these become stocked with a variety of fish during flooding. However, increases in local flood control and irrigation—contributing to increased weed infestation and eutrophication—have in many cases reduced the productivity of such naturally occurring fish lakes. The annual flooding also creates hardships for river-adjacent communities, destroying infrastructure, homes, livestock, and lives.
River Wildlife
Catfish, carp, featherbacks, and shad are among the 166 species of fish found in the Brahmaputra River. Giant freshwater prawns also thrive in the river and have long provided an important source of income for fishermen; however, aquatic farming of this resource has become more common than wild harvest. Other aquatic animals found in the river include the Gangetic turtle, soft-leathered turtle, the river dolphin, and the Indian gharial—all of which are endangered. The black soft-shell turtle has become extinct in the wild here. Until 2000, they lived in the wetlands of the Brahmaputra, where they fed on freshwater fish. Today, they only exist in a man-made pond sanctuary near Chittagong, Bangladesh, with a population of 150 to 300 turtles that are completely dependent on their human caretakers for survival.
The river dolphin, also known as the Ganges or Gangetic dolphin, is an endangered species numbering approximately 3,500 to 5,000 in the wild; it lives in the Ganges and Brahmaputra River systems of Nepal, India, and Bangladesh. These rivers run through one of the world's most densely populated areas, with pressures for river resources to provide water for irrigation and hydroelectricity. River habitat for the dolphins is threatened from more than 50 dams and other irrigation projects, as well as increased siltation and water pollution. The dolphins are also killed by being inadvertently caught in gill nets and other fishing gear.
The Indian gharial, a type of crocodile, is a critically endangered species that was previously thought to be locally extinct from the Brahmaputra River system. However, new fieldwork conducted from 2004 to 2007 found that the gharial population is fragmented, not extirpated, in the region. A limited number of individual gharials were found living in the upper Brahmaputra in isolated areas. In 2023, the population of gharials was estimated to be 259 in eight separate and fragmented habitats throughout Nepal and India.
Threats and Conflict
With a river that spans three countries, the potential for conflict and tensions is high over issues of upstream river usage and its downstream impact. The Brahmaputra originates in the Tibet autonomous province of China, where the Chinese have built a series of dams to generate electricity and to divert river water for irrigation projects. An unexpected flood in 2000 that destroyed an island village in northeast India was blamed on a burst earthen wall dam on a Brahmaputra tributary in China, an example of the type of cross-purposes that can lead to political crisis.
For its part, China claims that its upstream regulation of the river's flow can reduce downstream floods, mitigate downstream droughts, and reduce the country's carbon footprint through increased electricity generation from a nonfossil fuel source. India also has similar pressures for building dams and diverting water for energy creation and irrigation, which then raises additional uncertainty for Bangladesh, the nation at the mouth of the Brahmaputra-Ganges system.
Climate change has the potential to cause catastrophic flooding of the Brahmaputra River as the temperature continues to rise and snow melts earlier. Researchers believe that the warming climate will make the seasonal monsoon rains more intense, which will also cause frequent flooding.
Bibliography
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Krajick, Kevin. "Future Brahmaptura River Flooding as Climate Changes May Be Underestimated, Study Says." Nature Communications, 30 Nov. 2020, dx.doi.org/10.1038/s41467-020-19795-6. Accessed 21 Nov. 2024.
Panda, Ashish Kumar and Katdare, Suyash, et. al. “Population Status and Factors Influencing the Distribution of Critically Endangered Gharial (Gavialis gangeticus) in a Regulated Unprotected River System in India.” Global Ecology and Conservation, vol. 46, 2023, doi.org/10.1016/j.gecco.2023.e02547. Accessed 21 Nov. 2024.
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