Arun River between China Tibet and Nepal

Arun River between China Tibet and Nepal
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The Arun River (Nepali: अरुण नदी) is a major trans-boundary river that forms part of the Kosi River System (科西河系统), originating from the Tibet Autonomous Region (西藏自治区) of China. Known as Bum-chu (布姆曲) or Phung Chu (丰曲) in Tibet, the river flows through the Himalayan region and eventually merges with the Sun Kosi and Tamur River in Nepal to form the Sapta Kosi River (七个科西河).

It is one of the largest rivers passing through the Himalayas and is vital for both Nepal and Tibet.

Geography and Origin

Source and Tributaries

The Arun River originates near Gutso (谷措) in Nyalam County (聂拉木县), Tibet. It is fed by several tributaries, including Men-chu (门曲), Trakar-chu (查卡曲), and Yeru Tsanpo (耶鲁藏布), as well as Barun River (巴伦河), which join the river as it flows southward through the Himalayas.

  • Source: Gutso, Nyalam County, Tibet

  • Confluence: Joins Sun Kosi and Tamur River at Tribenighat, Nepal

The river flows through rugged terrain, carving a deep path between Makalu and Kangchenjunga mountains, forming one of the deepest valleys in the world. The river has an elevation of about 3,500 meters (11,500 feet) where it crosses the border from Tibet to Nepal.

  • Major Tributaries: Yeru Tsanpo, Trakar-chu, Barun River

  • Confluence with Sapta Kosi: Tribenighat, Nepal

Tibet: The Beginning of the Arun River

In Tibet, the river is called Bum-chu (布姆曲), which holds cultural significance. In Tibetan tradition, the name refers to a religious ceremony that tries to predict the year’s prospects based on the water levels in a pot or well. The word chu (曲) means water in Tibetan.

  • Tibetan Name: Bum-chu (布姆曲)

  • Nearby Regions: The river passes through Tingri County (定日县), Tingkye County (丁克县), and Kharda, which serves as the gateway to the Khangzhung east face of Mount Everest (珠穆朗玛峰).

Kosi River System: A Vital Waterway

The Arun River is a vital tributary in the Kosi River System (科西河系统), one of the largest river systems in Nepal. The system is composed of seven rivers, including Sun Kosi, Bhoté Koshi, Dudh Kosi, and Tamur River, which converge in eastern Nepal to form the Sapta Kosi (七科西河).

The Arun River contributes approximately 37% of the total water to the Kosi system, playing a crucial role in providing water to the region, especially during the monsoon season.

  • Kosi River System: The Arun contributes 37% of the total water.

  • Other Major Rivers: Sun Kosi, Dudh Kosi, Tamur River

Nepal: The River’s Journey South

Once the Arun River crosses into Nepal, it enters the monsoonal climate and experiences a dramatic increase in water flow, significantly altering the landscape. The region south of the border is characterized by steep terrain, unstable hill slopes, and a seismically active zone. The river supports a rich forest ecosystem in its northern part but is increasingly modified for agriculture in the southern regions.

  • Geography: Steep, dissected hillsides with unstable slopes

  • Annual Rainfall in Nepal: About 300 mm (12 inches) in Tibet, increasing significantly in Nepal

Human Activity and Ecology

The Arun River basin supports various ecosystems, particularly in its northern portion where the landscape is covered by mixed hardwoods, Chir pine, fir, and rhododendron at elevations over 1,000 meters. The southern portion of the basin, where most of the half-million inhabitants live, is characterized by agricultural land.

  • Vegetation: Mixed hardwoods, Chir pine, fir, rhododendron at higher altitudes

  • Population: The southern portion supports over half a million people living in scattered villages

Significance and Challenges

Seismic and Environmental Risks

The Arun River basin is located in an area prone to natural disasters, particularly earthquakes and landslides. In 1988, a major earthquake with a magnitude of 6.9 hit the region, causing significant damage and over 100 deaths in the basin. This earthquake highlighted the need for disaster mitigation and better infrastructure in the region.

  • Seismic Activity: The region is seismically active, with the 1988 Nepal earthquake as a notable event.

  • Landslides: Many areas are vulnerable to landslides, affecting both the river’s course and human settlements.

Cultural Significance

The Arun River, particularly in Nepal, is deeply embedded in the cultural practices and spiritual life of the local communities. The river is seen as both a source of livelihood and a spiritual symbol, with many temples and shrines along its banks.

  • Cultural Role: The river plays a key role in the local economy and spiritual practices.

Geographical Coordinates

  • Source Location: Gutso, Tibet Autonomous Region, China

  • Confluence: Tribenighat, Nepal

  • Coordinates: 26°54′47″N 87°09′25″E

The Arun River (阿伦河) is not only a critical water source for Nepal but also holds cultural, ecological, and geological importance. Its path from the Tibetan Plateau to Nepal represents a unique trans-boundary waterway that connects two countries, providing essential resources while also posing significant challenges for local communities in terms of environmental hazards and disaster management.