Upper Siang Dam: 114 scientists oppose project, express solidarity with indigenous communities

Hyderabad: As many as 114 scientists, researchers and conservation practitioners have issued a solidarity statement with the indigenous Adi communities of Beging and the wider Siang Valley in Arunachal Pradesh who are opposing the proposed Upper Siang Dam.

Hyderabad: In an open letter, the scientists explained the issues with the proposed dam in light of the recent floods that have caused widespread devastation and loss of life in the northeast.

“As we draft this statement of solidarity, northeastern India is facing a major ecological crisis, with Arunachal Pradesh among the worst affected,” the letter said.

Northeast floods

An early and intense monsoon onset has triggered flash floods, landslides and extensive destruction of infrastructure across multiple districts. Vehicles have been stranded, bridges and roads swept away, and homes inundated in river valleys.

The letter mentioned that field-level reports have confirmed that the most severe impacts have occurred in areas where road expansion or construction has destabilised slopes and in settlements located in floodplains, for example, Daporijo.

“The recent floods are a clear warning against further infrastructure expansion in geologically fragile, hydrologically active and ecologically irreplaceable landscapes like the Siang Valley. In this context, we extend our unequivocal solidarity to the communities of Beging and the broader Siang Valley, who are resisting the proposed Upper Siang Dam—officially termed the Siang Upper Multipurpose Project (SUMP),” the letter said.

What are the protests about?

The group said that the resistance of the locals reflects a grounded understanding of the ecological, cultural and socio-political risks the project entails, now underscored by the ongoing disaster.

Cultural and socio-economic considerations: The Siang River, originating in Tibet as the Yarlung Tsangpo, is the upper reach of the Brahmaputra and flows through Arunachal Pradesh and Assam before entering Bangladesh.

The river basin supports approximately 130 million people and spans about 0.58 million km² across Tibet, India and Bhutan. For the indigenous Adi communities, Ane Siang (Mother Siang) is both sacred and central to their cultural identity, livelihoods and their inherent ingenuity.

They hold deep-rooted socio-cultural and historical ties with the Ane Siang, whose flow and direction greatly shaped and enabled the migrations of many Adi communities over time. Hydropower construction involving tunnelling, road blasting and reservoir formation would disrupt the relationship the Adi people have with Ane Siang, the scientists said.

Compensation doesn’t replace everything

“Disrupting Siang would mean erasing the cultural identity of the Adi people. Past experiences with large dams in Northeast India (e.g., the Lower Subansiri and Dibang projects) show that displacement often leads to long-term socio-economic disruption,” the letter said.

Compensation mechanisms rarely account for non-monetary values such as land-based identity, ecological knowledge and customary rights. Relocation in mountainous terrain also involves high transaction costs that are frequently underestimated or ignored. Wild bioresources, traditional ecological knowledge (TEK), and indigenous agronomy communities in the Siang Valley depend on over 250 species of wild plants and animals for subsistence, medicine and cultural practices.

These include wild vegetables, bamboo shoots, fish, edible insects and medicinal herbs. This use is embedded in an intricate system of TEK that governs seasonal cycles, harvesting protocols, forest succession and weather prediction.

The region is also home to a unique, highly sophisticated system of terraced wet rice cultivation practised by indigenous Adi communities. Built along the hill slopes, this system uses gravity-fed irrigation channels fed by mountain streams and employs rotational nutrient cycling.

Terraced fields often support aquatic biodiversity, including seasonal fish harvests. These systems are integrated with shifting cultivation (jhum), tokko palm (Livistona jenkinsiana) groves, citrus orchards, and wild edible collection, forming a resilient, diversified agro-ecological matrix.

The Upper Siang Dam would submerge many of these terraces and disrupt irrigation systems, causing permanent loss of both farmland and traditional knowledge.

Geophysical and climatic risks: The Upper Siang Dam site falls in Seismic Zone V, the highest risk category as per the Bureau of Indian Standards.

The region has a history of major seismic events, including the 1950 Assam earthquake (M 8.6), one of the most powerful continental earthquakes ever recorded. Building large dams in such zones increases the risks of earthquake-triggered landslides, dam failure, and reservoir-triggered seismicity (RTS).

Climate change has also intensified the frequency of glacial lake outburst floods (GLOFs), cloudbursts, and slope failures in the region. The addition of tunnels, road networks, and heavy construction equipment would increase cumulative hazard potential, particularly downstream.

Geopolitical significance: The Siang originates in the Tibet Autonomous Region of China, making it strategically significant. Upstream hydropower and water diversion projects by China on the Yarlung Tsangpo have raised concerns over sediment flow, seasonal discharge, and water availability, the letter said.

In response, large infrastructure projects like the Upper Siang Dam are often framed as strategic counter-measures. However, these projects disproportionately burden the local communities in Arunachal Pradesh.

The imposition of such projects without broad-based consent undermines trust in governance and democratic institutions. Given the wider region’s complex history, exclusions from decision-making processes may cause alienation.

Communities have expressed their resistance through legal and democratic means. The state must include communities’ decision-making processes with accountability, transparency and respect for local agency.

Ecological and biodiversity value: The Siang Valley lies at the intersection of the Indo-Burma and Eastern Himalayan biodiversity hotspots. The valley harbours multiple species of conservation concern, including the Mishmi Takin (Budorcas taxicolortaxicolor), Red Panda (Ailurus fulgens), Bengal Florican (Houbaropsis bengalensis), and several hornbill, pheasant, and orchid species.

Siang Valley is also an important region which has played an important role in shaping current species distributions and enabling dispersals and seasonal migration. The Siang River basin is highly rich in aquatic diversity with many species that are found nowhere else. These include species that are adapted to life in torrential waters, such as catfishes of the family Sisoridae, loaches of the families Balitoridae and Nemacheilidae, some of which are only known from specific stretches of the river, and poorly studied species such as the recently rediscovered Ophichthys hodgarti.

All of them would be disproportionately affected by any alterations to the natural flow of the river. It is a hotspot of fish biodiversity, with over 100 species, including several newly discovered and highly endemic ones, dependent on its free-flowing, torrential waters.

The Upper Siang Dam stands to threaten this rich and deep ecological, cultural and economic value associated with this river and its bioresources, the letter said. Despite its ecological richness, the region remains under-surveyed. In the last 15 years alone, a staggering 37 species new to science have been described, along with 140 new distribution records and two rediscoveries.

What can be done?

Large-scale infrastructure projects like the proposed Upper Siang Dam threaten to irreversibly alter or destroy these ecosystems before they are fully studied and understood, the letter said.

The scientists demanded the following changes:

- The current and projected risks of climate-induced disasters, seismic activity, and infrastructure failure render the Upper Siang Multipurpose Project unsafe and unsustainable.

- We urge the Union and State Governments to suspend all construction, surveys and pre-clearance activities related to the Upper Siang project, ensure full recognition of community forest and resource rights under the FRA, and uphold the principle of Free, Prior and Informed Consent (FPIC).