In the forested valleys of Arunachal Pradesh, the Siang River flows south from the Tibetan Plateau before entering India, where it becomes a critical part of the Brahmaputra river system. The proposed Siang Upper Multipurpose Project (SUMP) has placed this river at the center of an ongoing policy, environmental, and geopolitical debate. The Indian government views the project as a strategic infrastructure initiative aimed at improving hydropower generation, reducing flood risks, and long-term water security in a region where river flow is influenced by conditions upstream in China. At the same time, the project has faced sustained concern from indigenous Adi communities and residents in the Siang valley. For many, the river, locally known as Ane Siang or Mother Siang, is closely tied to agricultural practices, cultural identity, and religious beliefs. Any major alteration to its flow is not just an environmental change for them but considered a disruption to their identity and way of life.
The SUMP sits at the center of this tension. To supporters, it represents one of India’s most important efforts to secure water and generate hydropower in a geopolitically sensitive region. To critics and many residents, it raises deep concerns about displacement, ecological damage, and the erosion of indigenous rights.
This river originates in Tibet as the Yarlung Tsangpo before entering Arunachal Pradesh as the Siang and eventually becoming the Brahmaputra in Assam and the Jamuna in Bangladesh. Because of this location, decisions made on the Siang have implications far beyond Arunachal Pradesh. This single river system sustains the livelihoods of an estimated 130 million people in India and Bangladesh, with significant contributions to India’s overall surface water resources and a major share of its Himalayan hydropower potential.
What the SUMP Actually Is
The Siang Upper Multipurpose Project is a proposed mega-dam on the Siang River in Arunachal Pradesh’s Upper Siang and Siang districts, with the National Hydroelectric Power Corporation (NHPC), India’s state-owned hydropower utility, likely the implementing agency if the project moves forward. The proposal remains in the planning and pre-construction stage and has not yet reached final execution approval. The project was initially conceptualized as two separate hydropower developments- Siang Upper Stage I with an estimated capacity of around 6,000 MW and Stage II at roughly 3,750 MW. After consultations between the Government of Arunachal Pradesh and central planning institutions such as NITI Aayog, the concept was consolidated into a single large storage-based project. The revised plan now puts the project at about 11,000 MW, making it far larger than the original proposal. Under the revised plan, the dam is expected to be around 250–300 meters high, making it one of the largest hydropower projects proposed in India.
Multiple potential sites have been examined for the project, including locations near Parong and Dite Dime in the Siang district, as well as Ugeng in Upper Siang district. Among these, Parong has often been considered less feasible due to its proximity to the Advanced Landing Ground at Tuting, which introduces both technical and strategic constraints related to aviation safety and border infrastructure.
A September 2024 NHPC cost estimate for the Siang Upper Multipurpose Project is approximately $10 billion to $13.2 billion, depending on design configuration and cost assumptions. Its reservoir would hold approximately 9 billion cubic meters of water, designed to regulate seasonal flows of the Siang River.
China’s Medog Hydropower Project Upstream
In December 2024, China formally approved a large hydropower development on the lower reaches of the river near the Great Bend in Medog County, in the Tibet Autonomous Region. Construction was publicly started in July 2025, when Chinese Premier Li Qiang presided over the groundbreaking ceremony, signaling its importance as a national priority infrastructure project. The project, commonly referred to as the Medog Hydropower Station, is designed as a five-stage cascade of hydropower stations built along a short but extremely steep section of the river. At this location, the Yarlung Tsangpo makes a sharp U-shaped turn around Namcha Barwa Peak and drops nearly 2,000 meters in elevation over a stretch of about 50 kilometers, creating one of the highest energy-density hydropower zones in the world. This extreme gradient is the primary reason for the project’s large generating capacity.
Once completed, the complex is expected to have an installed capacity of approximately 60 gigawatts, with annual electricity generation estimated at around 300 billion kilowatt-hours, making it significantly larger than the Three Gorges Dam in terms of power capacity. The project is also among the most expensive infrastructure undertakings ever approved, with total investment estimated at around 1.2 trillion yuan (approximately $165 billion).
Beijing describes the Medog Hydropower Project as a “project of the century” that will support economic development in Tibet by creating thousands of construction jobs, expand grid connections into Sichuan and Yunnan, and supply electricity to high-demand industrial regions in eastern China through long-distance transmission under the west-to-east power transfer framework. While Chinese officials maintain that the project will operate primarily on a run-of-river basis and will not significantly reduce downstream flows, its location near the disputed Sino-Indian border and the limited transparency regarding operational data have raised concerns in downstream countries, particularly India and Bangladesh, over its potential long-term hydrological and strategic implications.
Why the Brahmaputra Remains a Strategic Weak Point for India
India and China do not have a binding agreement on how the Brahmaputra River should be shared or managed. Unlike the Indus Waters Treaty between India and Pakistan, there is no detailed legal system that controls water use, data sharing, or dispute settlement for this river. Instead, cooperation depends mainly on a few data-sharing memorandums of understanding, operating on goodwill only. This creates an uneven situation where China, as the upper riparian country, has more control over the river’s flow before it enters India.
This imbalance becomes most visible during periods of disruption in data sharing. In 2017, following the intense 73-day Doklam border standoff between Indian and Chinese troops, China temporarily stopped providing flood-season river data to India. Beijing claimed that data could not be sent due to technical upgrades and renovations at its Tibetan monitoring stations. However, this explanation was heavily scrutinized when it was revealed that China had simultaneously continued sharing seamless, real-time data with Bangladesh from the exact same river basin. The lack of advance warning left India unprepared for flooding in Assam, leaving riverside communities to face severe consequences.
Moreover, in June 2000, a massive surge of water rushed from Tibet into the Siang River, causing terrible flash floods in Arunachal Pradesh. This happened because a large natural dam made of landslide debris abruptly broke on the Chinese side. Even though satellite imagery later showed that the barrier was failing, Beijing gave no official warning or water data to New Delhi. This lack of advance notice left downstream communities completely unprepared. As a result, the sudden flood killed more than 30 people, destroyed bridges, wiped out many local villages, and left thousands of people homeless.
The SUMP is designed as a “hydraulic cushion” to address this structural asymmetry of China holding the upper-riparian advantage, mitigating risks of water diversion or flooding from upstream projects like the one in Medog. India’s foreign ministry spokesperson Randhir Jaiswal, responding to China’s Medog groundbreaking, said, “We will continue to monitor and take necessary measures to protect our interests.”
Union Minister Kiren Rijiju, speaking at a function in Itanagar on June 10, 2025, described the SUMP as a “strategic necessity” for India’s national security, pointing towards China’s expanding hydropower developments upstream on the Yarlung Tsangpo, including two major dam sites near the Great Bend and Medog, as issues that demand India’s attention. Arunachal Pradesh Chief Minister Pema Khandu has been similarly direct regarding the project’s geopolitical role. Speaking on December 19, 2024, in Boleng, Khandu said that the SUMP is essential for flood control and mitigating potential water surges from upstream Chinese operations. He emphasized that the project’s primary goal is to manage the Siang River, with hydropower being secondary.
This project serves as a “hydrological deterrence” for India, providing a massive water-storage buffer to mitigate flood risks, manage drought, and neutralize sudden upstream water releases from China. Furthermore, the project reinforces India’s physical and administrative governance over Arunachal Pradesh, a border state that China continues to claim as part of what it calls South Tibet. Covering nearly 90,000 square kilometers and home to over one million people, Arunachal Pradesh remains one of the most sensitive areas in the Sino-Indian territorial dispute. Beijing has repeatedly objected to Indian infrastructure projects in the state and has periodically issued Chinese names for towns, villages, and geographical features there. For example, in 2024 China released another list of renamed locations in Arunachal Pradesh, a move that India dismissed as an attempt to reinforce territorial claims through symbolism rather than legal authority.
The Adi People’s Objective
The Adi are the dominant indigenous community of the Upper Siang and Siang districts, who have inhabited these valleys for centuries and whose agricultural, spiritual practices, and cultural identity are inseparable from the river. Community groups such as the Siang Indigenous Farmers’ Forum (SIFF), a civil society body representing thousands of affected families across three districts, argue that no meaningful consent has been given for either surveys or construction, and that the project threatens ancestral land and livelihoods.
Their opposition is not recent. As SIFF founder Oyar Gao explained, “Our resistance began in the 1980s when the Brahmaputra Board first proposed a dam on the Siang… Today, the narrative has shifted to concerns about China. But for us, it has always been about safeguarding our river and our land.” The opposition has also drawn on traditional institutions. In 2025, the Bogum Bokang Kebang, a high council of Adi customary governance, was reconvened after decades to formally discuss the project, highlighting the scale of concern within community structures.
Resistance has also taken culturally specific forms. Communities have conducted rituals invoking river and forest spirits, symbolic acts intended to assert moral authority over the landscape. Villagers have blocked survey access routes, dismantled bridges, and performed cleansing ceremonies at drilling sites. Within Adi cosmology, these are not symbolic gestures alone, but direct forms of intervention grounded in spiritual obligation. Women in several villages have maintained nightly vigil along riverbanks, monitoring survey activity. According to SIFF members, earlier attempts at “clandestine” surveys were intercepted by villagers.
SIFF, along with the Adi Student Union and the apex tribal body Adi Banne Kebang, has consistently rejected the project and refused any participation in pre-feasibility surveys. According to SIFF, the proposed dam could displace over 1.5 lakh people, mostly from the Adi and other indigenous tribes, and submerge 27 villages, leading to the loss of ancestral homes and land rights. Some of the oldest Adi settlements, including culturally significant villages such as Riga, are among those at risk. Community members have drawn explicit parallels to the Chakma and Hajong people displaced by Bangladesh’s Kaptai Dam in the 1960s, as a warning of how many people can be displaced if anything happens to India’s largest hydroelectric dam, the Siang dam.
For the Adi people, the concern extends beyond displacement. It is also about the possibility of losing a cultural landscape built over generations. “If we are to leave this land, where will they settle us? Who will give us their land?” asked one community leader in an interview conducted in Upper Siang. The Siang valley is a cultivated landscape of terraced rice fields, jhum plots, and orchards that sustain household economies. Farmers describe earning steady incomes from orange and pineapple cultivation, but also express fear that displacement would erase both livelihood and identity. One farmer from Parong stated they do not want their children to grow up “separated from their land.”
Tensions escalated sharply in December 2024 when Arunachal Pradesh’s Home Ministry sent letters to Deputy Commissioners of Upper Siang, Siang, and East Siang districts requesting logistical arrangements for the deployment of central armed forces to facilitate the pre-feasibility survey. As many as 100 armed personnel of the Central Armed Police Forces (CAPF) were subsequently deployed in Siang and Upper Siang districts. The SIFF responded with an immediate call for an indefinite sit-in at Beging, the proposed survey site, opposing what they described as the forced militarization of their homeland. Protesters, particularly women, attempted to march toward the site but were stopped by barricades.
This has led to growing tensions between state agencies and local villagers over land use, school infrastructure, and the presence of paramilitary forces. The project has also deepened internal divisions. Social media videos show villagers confronting one another over consent signatures and water access, with accusations of betrayal circulating within and between clans. Reportedly, some residents have been incentivized through local committees and exposure visits to other dam sites, further intensifying mistrust.
On May 23, 2025, even as protests intensified, the state government announced that it had secured an MOU with two residents of Pangkang village, Taba Tamut and Bakin Tali, who claimed to represent their community’s consent to the pre-feasibility survey. The MOU outlined a development package of Rs 5 crore over three years. In reality, as anti-dam activist and environmental lawyer Ebo Mili said, only two or three people signed the MOU, and the rest were completely unaware of any such agreement. Mili compared the approach to the government’s handling of the Idu Mishmi community during the Dibang Multipurpose Project when “same tactics of misinformation and a divide-and-rule policy were used” and asked whether the Rs 5 crore offer constituted an “open bribe with public money.”
The confrontation entered a more alarming phase when Ebo Mili was detained in May 2025, allegedly for leading a protest at the Beging survey site. The Siang Deputy Commissioner lodged a complaint at Boleng police station, alleging that Mili had led a “mob” of 80 to 90 individuals under the SIFF banner to disrupt survey activities. Mili, a vocal critic of the state government’s policies on mega projects, had already been detained twice previously. He temporarily fell out of contact following the complaint, prompting international alarm from advocacy organizations across the Asia-Pacific. The Asia Indigenous Peoples Network on Extractive Industries and Energy and the Right Energy Partnership with Indigenous Peoples issued a joint statement of concern, calling on the Government of India to conduct an impartial investigation and ensure Mili’s safety. An update on May 29, 2025, confirmed that Mili had been located, though advocacy groups noted they remained concerned about his safety as well as the safety and security of the Adi communities more broadly.
Alongside rising tensions over surveys and militarization, recently there have been direct attacks on political figures linked to the project. In Upper Siang, the residence of a local MLA was vandalized during a wave of protests against the SUMP in June 2026. Crowds reportedly gathered around the legislator’s home and damaged parts of the property amid escalating anger over the project and its perceived imposition on local communities.
However, as of early 2026, several villages have signed MOUs permitting the pre-feasibility survey to proceed, while others have refused entirely. In March 2026, 56 of 77 households in Bomdo village in Upper Siang district signed an MOU formally extending their consent. Earlier, only a few villages had joined the process. The government has pointed to these developments as evidence of growing community support, while opponents maintain that the consent process remains compromised by financial incentives, inadequate information, and the presence of armed personnel in communities make them feel they have little choice but to comply.
Downstream Concerns
The geopolitical implications of the SUMP extend far beyond Arunachal Pradesh. Bangladesh, as the terminal riparian state of the Brahmaputra-Jamuna basin, would be profoundly affected by any significant alteration of the river’s seasonal flow patterns, whether caused by China’s Medog complex or India’s SUMP. Although only about 8 percent of the Brahmaputra basin lies within Bangladesh, the river system contributes over 65 percent of the country’s water supply, making it widely described as the “lifeline of Bangladesh.”
In this situation, any upstream action, whether from China’s upper basin developments or India’s SUMP, inevitably raises concerns in Dhaka about changes in river flow, seasons, and sediment movement. The main risk is not that the water will disappear, but that the river will become more unpredictable in a system that is already affected by extreme monsoon changes. As Sheikh Rokon, the secretary-general of Riverine People, a Dhaka-based water rights organization, said, the emerging pattern of “the ‘dam for a dam’ race between China and India will impact us most adversely,” highlighting Bangladesh as a country with limited capacity to adapt to sudden hydrological shifts.
For India, the Siang dam is viewed by planners as a potential risk-management tool against upstream variability, offering limited capacity to regulate seasonal flows, improve flood forecasting, and stabilize dry-season water availability. However, hydrologists and policy experts caution that in a monsoon-dominated system as vast as the Brahmaputra River, no single dam can meaningfully control basin-wide hydrology. The more realistic outcome is not control but improved coordination, data exchange, and regional leverage.
In India, the Brahmaputra River basin supports approximately 83 million people, with 34% residing in Assam, where the river acts as a primary economic driver across major floodplain districts like Dhubri, Goalpara, Barpeta, Nalbari, Darrang, and the 352-square-kilometer river island of Majuli. While seasonal monsoons cause massive short-term infrastructure damage, they deposit vital, nutrient-rich alluvial silt across millions of hectares of farmland, replenishing groundwater and sustaining rice crops that account for 96% of the state’s total food grain production and occupy nearly 70% of its gross cropped area.
Bangladesh relies heavily on water that comes from outside its borders, with about 91% of its rivers flowing in from upstream. The Brahmaputra (Jamuna) alone provides around 70% of the country’s yearly freshwater flow. This river supports the lives and food security of more than 34 million people, especially in northern districts like Kurigram, Gaibandha, Rangpur, Jamalpur, Sirajganj, and Bogura. It also plays a key role in agriculture, which employs nearly half of the rural population (48%) and contributes about 16% to national GDP. The region produces the crucial dry-season Boro rice crop, covering about 4.8 million hectares and producing over 21 million metric tonnes (55% of national rice production). Along with this, it also supports monsoon Aman rice, river fisheries, and large-scale jute farming. Even a small 10% drop in dry-season water can threaten national food security, while heavy monsoon changes can flood up to 30% of the delta.
Downstream regions remain highly dependent on upstream water management, and this risk could increase with the expected expiration of the 1996 Ganges Water Sharing Treaty in December 2026. Signed for a strict 30-year term to govern dry-season flows at the Farakka Barrage, the renewal of this treaty must not fail, as its collapse could trigger a catastrophic water security crisis, accelerate severe salinity intrusion, and disrupt the livelihoods of over 60 million people across southwestern Bangladesh.
The 1996 accord primarily only addressed water sharing in terms of the Ganges dispute, and it was legally limited to that single river basin. Because India and Bangladesh share 54 transboundary rivers, a separate, independent legal mechanism was required to be drafted and signed in 2011 specifically for the Teesta River. This 2011 draft treaty proposed allocating 37.5% of the Teesta’s dry-season flow to Bangladesh, but it was abruptly frozen due to intense domestic political opposition from West Bengal over local irrigation demands.
Without a clear and binding agreement, Bangladesh’s northern farming regions face serious water shortages during the dry season. In response to this ongoing “water aggression,” the Bangladesh Nationalist Party (BNP) mobilized massive 48-hour sit-ins and marches across Rangpur Division in February 2025. Protesters demanded a fair share of the water and the immediate implementation of a comprehensive Teesta Master Plan to protect rural livelihoods.
This momentum grew throughout the year into a structured campaign to pressurize the then interim government before upcoming elections. Organized by the “Teesta River Protection Movement” and led by senior BNP figures like Asadul Habib Dulu and Barrister Hasan Rajib Pradhan, another mass demonstration took place on 5 October 2025, where formal protest letters were submitted to local Deputy Commissioners. This was followed by evening torchlight rallies on 16 October 2025, covering a 130-km stretch of riverbanks across Lalmonirhat, Kurigram, Rangpur, Nilphamari aand Gaibandha. The movement issued a strict ultimatum demanding that the government officially begin working on the 12000-crore BDT Teesta Master Plan by November 2025.
The human cost of poor coordination in river management became clear during the August 2024 floods. Sudden upstream water releases, combined with heavy monsoon rains, flooded districts like Feni, Cumilla, and Noakhali, killing 71 people and destroying farmland and fisheries. The disaster exposed a major gap in cross-border cooperation- there was no real-time data-sharing system to warn downstream communities in advance. To conclude, the SUMP will affect not only Arunachal Pradesh but also millions of people downstream, especially in Bangladesh. As the last country along the Brahmaputra-Jamuna river system, Bangladesh is highly dependent on the river for farming, fishing, transportation, and water supply. Any major change in river flow could have consequences for livelihoods and food security. Combined with existing concerns over the unresolved Teesta water-sharing agreement and recent flood-related disputes, the project highlights the need for transparency, data sharing, and cooperation among all countries that share the Brahmaputra basin.
Verification Note: The information in this report has been compiled from multiple credible sources and cross-checked for consistency. Data and reports have been used to corroborate events where possible. While every effort has been made to ensure accuracy, access limitations may prevent independent verification of all details. Map created using Google My Maps.
Afiya Ibnath Ayshi is a Security and Strategic Reporting Fellow at Bangladesh Defence Journal. She covers defence, foreign affairs, and humanitarian issues, focusing on how regional and global developments influence Bangladesh’s security and diplomacy. A graduate in English from the University of Dhaka, she brings a research-based and balanced approach to her work.