Risk from China’s upstream dam
The Siang River enters India from Tibet, where it is known as the Yarlung Tsangpo. China has begun building a very large hydropower project on this river in the Nyingchi (Medog) region, close to the Indian border. The project has an estimated installed capacity of 60,000 MW and is reportedly targeted for completion by 2035. The Government of India estimates that the Medog dam will be able to store about 5.5 billion cubic metres (BCM) of water.
This water storage gives immense leverage to China over the lives, livelihoods and properties of people of Arunachal Pradesh, especially the Siang region, and ultimately over Assam and even Bangladesh. The Siang River joins the Dibang and Lohit rivers to form the mighty Brahmaputra, which supports millions of people through farming, fishing, inland water transport and drinking water. If water is stored or diverted in winter, both rivers could carry far less water. If the dam traps silt, fertile lands could suffer. There are also concerns that the project could help divert water towards China’s dry northern regions, which has been a strategic ambition and national priority for China over at least the past 4 decades. How much diversion may take place, and how it would affect water availability downstream, needs detailed scientific study rather than assumptions. Any significant diversion of the Siang’s water could have devastating consequences for downstream areas in India.
The risks are not limited to changes in flow. A large dam in an earthquake-prone and geologically sensitive Himalayan region raises concerns about extreme natural events, structural failure or emergency releases of water. Whether deliberate or caused by an accident or earthquake, a sudden release of water could cause flash floods in the Siang valley. There is no guarantee that such risks can always be prevented through diplomatic talks, or that enough advance warning would be available. Past events show how real these dangers are. If a disaster like the floods in Nepal on 26 August 2026 or the flood of 11 June 2000 were to strike the Siang today, we would have no protective measures in place for people and their property.
At present, India and China do not have a water-sharing treaty. The Memorandum of Understanding for sharing hydrological data on the Brahmaputra expired on 5 June 2023 and has not been renewed, increasing uncertainty regarding the timely availability of information on upstream river conditions. The need for cooperation on trans-border rivers, including resumption of provision of hydrological data has been highlighted by the Union Government in several high-level interactions with China, but no response has been received.
Siang Upper Multipurpose Project
The Siang Upper Multipurpose Project (Siang UMP) has been proposed as a response to this risk. Considering its strategic importance for India’s water and national security, the Government of India has declared the SUMP a National Project in 2008. Its proposed storage capacity is about 9.2 BCM, considerably more than the estimated capacity of the Medog dam. A reservoir of this size could absorb sudden surges of water released from upstream and help keep the river flowing in lean periods. It would act as a safeguard for downstream areas while also producing clean electricity and supporting flood control. Whether such a project is feasible, and in what form, must first be established through proper scientific study.
What is PFR?
The SUMP has become a subject of strong public debate in the Siang region and concerns about the environment, displacement and community rights are valid. However, much of the current opposition is premature and likely stems from an incomplete understanding.
The PFR is the stage where facts are gathered. Without it, neither the Government nor the people can know whether the project is safe, what its effects might be, or whether alternatives would be better. A Pre-Feasibility Report is the first technical study carried out for any proposed hydropower project in India. It does not approve of the building of a dam. It is not a construction plan, and it does not transfer any land.
Its purpose is to find out whether a project at a given location is possible and, if so, in what broad form. Engineers and scientists study the rocks, soil, slopes, river flows and earthquake risk of the area. From this, they judge whether a site is safe and practical enough to be studied further. If the findings are unfavourable, the project can be changed, moved to a different site or dropped altogether. The name itself is illuminating. It is called a Pre-Feasibility Report, not even a Feasibility Report.
The field work under a PFR is limited and temporary. It includes surveys of the terrain, river valley, slopes and geological conditions, along with geophysical investigations to understand subsurface features. Exploratory boreholes are drilled at selected locations along the proposed dam axis to obtain rock samples from below surface and early information on foundation conditions.
No effects on people in the area
The PFR does not materially affect the area. No village is relocated, no land is acquired, no reservoir is created and no river is diverted because of a PFR. No large-scale clearing of forests takes place, and the Siang continues to flow as before.
The land required for the PFR is very small. Drilling will take place at the Parong, Beging, Ugeng and Komkar sites. At each site, two boreholes will be drilled, with each drilling location requiring an area of about 20 m × 20 m (400 sq m). Together, all eight drilling locations will require only about 3,200 sq m of land, which is less than half the size of a standard football field.
These sites are temporary and can be restored once the work is completed. Farming, fishing and daily life in the surrounding villages carry on normally.
No dam without the people’s consent
The most important takeaway is that the PFR is not the stage at which the project is decided. The Government has made it clear that no dam can and will be built without informed consent of people. The State Government has already signed MOUs with 48 villages of Siang and Upper Siang Districts assuring the same. This assurance is also backed by the law.
Section 3 of Environment (Protection) Act, 1986 and the Environmental Impact Assessment Notification, 2006 requires a detailed study of a project’s effects on forests, wildlife, rivers and communities. As part of this process, a public hearing must be held in the affected area in the local language. People can raise their objections and concerns at this hearing, and this must happen before any environmental clearance is considered.
Similarly, Section 4 of the Right to Fair Compensation and Transparency in Land Acquisition, Rehabilitation and Resettlement Act, 2013 requires a Social Impact Assessment before any land acquisition process can proceed. The assessment includes consultations and public hearings with affected families and local communities. The Act also guarantees fair compensation, rehabilitation and resettlement, and requires the entire process to be conducted in a transparent manner. Section 38 of the Act also requires that all rehabilitation and resettlement works are completed at 6 months prior to any submergence. In addition, any use of forest land requires forest clearance and the rights of forest-dwelling communities must be recognised under the Forest Rights Act, 2006. Consultation with village councils, Gram Sabhas and community bodies are therefore essential at every later stage.
Conclusion
In simple terms, the PFR answers the question “Is this possible?”. Some people are asking the question, “Should this happen?”. The second question cannot be answered properly without the first. Allowing the PFR to go ahead does not mean agreeing to the dam. It means that when the time comes to decide, the people of Siang and Upper Siang will decide with full knowledge of the facts.
Atek Miyu is retired Chief Engineer, Department of Hydro Power Development, Arunachal Pradesh. Views expressed are personal.
