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The Siang River of Arunachal Pradesh: Geography, Ecology and Conservation

Siang River: Lifeline of Arunachal Pradesh
The Siang River is the largest tributary of the Brahmaputra River system in Northeast India. Originating from the Chema Yungdung glacier near Kubi in Tibet at an elevation of 5,150 meters, the river is known as Tsangpo in Tibet. The Tsangpo flows in a west-east direction for 1,625 kilometers in Tibet before entering India near Tuting in the Upper Siang district of Arunachal Pradesh.
In India, the river flows in a north-south direction for about 52 kilometers through the East Siang district of Arunachal Pradesh, before meeting the Lohit and Dibang rivers in Assam. The combined rivers then become the mighty Brahmaputra River. The Siang River basin covers over 30,000 square kilometers in the eastern Himalayas.
Here, the UCN Team’s detailed analysis of siang RIver, alongwith Siang river maps to present key concepts and insights on this largest Brahmaputra Tributary.
The Siang River is the lifeline for many indigenous tribes inhabiting Arunachal Pradesh and Assam, including the Adi, Memba and Khamba tribes. The river supports the livelihoods and culture of these communities through fishing and agriculture. It is also vital to the ecology of the region as it supports some of the richest biodiversity in Northeast India. The Siang River basin is one of the global biodiversity hotspots, home to thousands of floral and faunal species. Thus, the Siang River holds great ecological, cultural and economic significance for the eastern Himalayan region.
Geography and Climate of Siang River
Location and Course

The Siang originates from the Chema Yungdung glacier located near Kubi in the Tibetan Plateau at an elevation of 5,150 meters. In Tibet, the river is known as the Tsangpo and flows in a west-east direction for around 1,625 kilometers.
The key details about the course of the Siang/Tsangpo River are:
- Origin: Chema Yungdung Glacier, Tibet
- Known as Tsangpo in Tibet
- Major cities along the Tsangpo in Tibet: Lhasa, Shigatse
- Enters India in Upper Siang district of Arunachal Pradesh near Tuting
- Known as Siang River in India
- Flows through East Siang district in Arunachal Pradesh
- Major city along Siang River: Pasighat
- Travels nearly 52 kilometers in India before reaching Assam
- Joins Lohit and Dibang rivers in Assam
- Combined rivers form the Brahmaputra River
- Brahmaputra flows through Assam and Bangladesh before emptying into Bay of Bengal
So in short, the River Siang starts as the Tsangpo in Tibet, enters India in Arunachal Pradesh near Tuting, flows briefly through the Siang valley, before joining other tributaries and forming the Brahmaputra River.
Climate and Rainfall Patterns
The climate in the Siang River basin varies from temperate to tropical depending on the altitude and extent of exposure to the sun.
In the upper reaches in the Himalayas, the climate is cold with heavy snowfall during winter when temperatures can fall below 0°C. During summer, the maximum temperature in the higher altitudes occasionally exceeds 37°C.
In the lower altitudes of the foothills and plains, the climate is generally warm and experiences a tropical monsoon type of weather.
The River Siang basin receives heavy rainfall during the monsoon season from May to October. The rainfall pattern is dominated by the tropical storms originating in the Bay of Bengal.
July records the highest rainfall, receiving almost 85% of the annual precipitation. The northern parts of the basin receive around 2,500 mm rainfall annually, while the southern parts receive over 3,000 mm due to more intense monsoons.
During the monsoon months, flooding is common across the Siang River basin. The heavy discharge of water causes the river to overflow its banks and inundate the surrounding plains and tributaries. Communities living along the river are prone to facing flood damage almost every year during the monsoon.
People and Culture
The River Siang basin is inhabited by several indigenous tribal communities including the Adi, Memba and Khamba tribes. These communities are heavily dependent on the Siang River for their livelihoods and culture.
Fishing is one of the most common professions as the Siang River harbors abundant fish diversity. Apart from fishing, agriculture also forms an important source of livelihood with communities practicing wet rice cultivation, horticulture, vegetable farming, etc. along the river plains.
Many tribal villages, religious sites and monasteries are situated along the banks of the Siang River highlighting its cultural significance in the daily lives of the people.
Siang River Festival
The Siang River holds great cultural significance for the indigenous tribes inhabiting Arunachal Pradesh. This is highlighted by the annual Siang River Festival organized in the state. The festival aims to promote tourism, cultural heritage and eco-tourism in the Siang River basin region.
It is organized by the District Administration of West Siang in collaboration with the state’s Department of Tourism. The week-long festival showcases the rich cultural diversity of Arunachal Pradesh through activities like traditional boat racing, elephant racing, folk dances, food festivals and adventure sports like river rafting and paragliding. The festival provides a platform to celebrate the ethnic harmony of the state and promotes the area’s natural beauty and biodiversity.
It also serves as an initiative to support local communities affected by wildlife crop damage. By bringing together the tribes like Adi, Memba and Khamba, the Siang River Festival contributes to the preservation of indigenous cultures and habitats dependent on the river. Through cultural showcasing and eco-tourism promotion, the festival highlights the vital significance of conserving the ecological and cultural heritage sustained by the Siang River basin.
Ecology and Biodiversity
Flora
Flora: Nearly 82% of the state of Arunachal Pradesh where the Siang River basin is located is under dense forest cover. The river supports luxuriant growth of forests consisting of oaks, pines, rhododendrons, birches and orchids. The floral biodiversity is among the richest in the entire Himalayan range.
Fauna
Fauna: The Siang River basin harbors incredible faunal diversity. The river and its tributaries are home to 185 fish species including the golden mahseer, snow trout and catfish.
The river basin also supports diverse mammalian species like tigers, elephants, clouded leopards, civets, bears, deer etc. Over 500 species of birds are found in the region including hornbills, pheasants and parakeets. The rich ecology underlines the conservation significance of the Siang River system.
Threats and Conservation
Threats and Conservation
In recent decades, the Siang River has faced multiple threats from human activities:
- Growing population and urbanization has led to increased dumping of sewage and solid waste into the river, causing water pollution.
- Deforestation in the catchment area has increased soil erosion and changed natural flow patterns.
- Unregulated fishing practices are depleting fish stocks.
- Hydropower projects are impacting water volumes and flow.
- Climate change is affecting rainfall and glacier melt.
These threats are drastically impacting the ecological health and biodiversity of the Siang River basin. The rich diversity of flora and fauna along with tribal livelihoods dependent on the river are under grave risk.
Thus, it is crucial to implement conservation strategies focused on:
- Protecting remaining forests and tributaries.
- Regulating developmental projects.
- Promoting sustainable fishing and agriculture.
- Checking pollution by treating sewage and waste.
- Maintaining natural water flow patterns.
Final Thoughts
In the UCN team’s opinion, the Siang River basin is a globally significant biodiversity hotspot providing livelihoods to indigenous communities. However, growing anthropogenic pressures risk the ecology and local cultures sustaining in harmony with the river. Urgent conservation efforts are needed to maintain the free flowing Siang River along with its surrounding biodiversity and tribal heritage for current and future generations. The river sustains life in the eastern Himalayas and its conservation value cannot be overlooked.