The Arun River is a major trans-Himalayan river that originates in Tibet and flows through the eastern part of Nepal, contributing significantly to the Sapta Koshi River system. Revered for its geographical significance and natural beauty, the Arun River is one of the most important rivers in the Himalayas.

Quick Facts

• Origin: Near Mount Shishapangma, Tibet Autonomous Region, China

• Length: Approx. 320 km (200 miles) within Nepal

• Mouth: Confluence with the Sun Kosi and Tamur Rivers to form the Sapta Koshi

• Major Countries: China (Tibet), Nepal

• Elevation Drop: One of the world’s greatest river elevation drops over a short distance

Geographic and Hydrological Significance

Source and Course

The Arun River, known as Phung Chu or Bum Chu in Tibet, rises near the Tibetan Himalayas and travels southward, piercing through the formidable Himalayan mountain range. It enters Nepal in the Sankhuwasabha District, carving one of the deepest valleys in the world.

Role in the Koshi River System

In Nepal, the Arun River joins with the Sun Koshi and Tamur Rivers to form the Koshi River, also called the “Sorrow of Bihar” due to its historical flooding in northern India. The Koshi eventually flows into the Ganges.

Cultural and Historical Context

Spiritual Relevance

In both Tibet and Nepal, rivers like the Arun are seen as sacred. The Tibetan name “Bum Chu” is associated with spiritual traditions in Tashilhunpo Monastery, where the river is part of a water divination ritual held annually to predict the future.

Local Communities

The Arun Valley is home to diverse ethnic groups including the Rai, Sherpa, and Tamang communities. These communities rely on the river for agriculture, fishing, and as a source of freshwater.

Ecology and Biodiversity

Arun Valley Ecosystem

The Arun River Valley supports a wide range of flora and fauna. Due to its varied altitude and climate zones, it hosts:

• Himalayan black bears

• Red pandas

• Musk deer

• Over 600 bird species

This makes it a hotspot for biodiversity and a critical corridor for wildlife migration between protected areas.

Hydropower Potential and Development

Arun III Hydroelectric Project

One of the most ambitious infrastructure projects in Nepal, the Arun III Hydropower Project is a 900 MW development funded by India. It’s designed to harness the river’s immense flow for electricity generation, supporting both Nepal’s energy goals and regional power trade.

Key Features:

• Run-of-the-river project

• Located in Sankhuwasabha District

• Expected to be a game changer for Nepal’s economy

Trekking and Adventure

Arun Valley Trek

For trekkers seeking off-the-beaten-path adventures, the Arun Valley Trek offers a less crowded alternative to the Everest Base Camp route. It features:

• Lush forests and terraced hillsides

• Traditional villages

• Panoramic views of Everest and Makalu

This trek is popular among eco-tourists and adventure seekers.

Conclusion

The Arun River is more than just a waterway — it’s a source of life, culture, power, and ecological diversity. As Nepal balances development and conservation, the Arun River continues to play a crucial role in shaping the landscape and livelihoods of the eastern Himalayas.