The project and apprehensions: The Yarlung Tsangpo hydropower project on the upper Brahmaputra is poised to become the world’s largest hydropower project, planned at the “Great Bend” of the river in Medog county, Tibet. Since its announcement in November 2024, concerns have emerged regarding its possible implications for Assam and other downstream areas. Key issues include reduced water availability in India, agricultural consequences, biodiversity loss, and long-term ecological repercussions.
Probable development options: The Mega hydroelectric project capitalizes on the huge drop(head) of about 2300m while the Yarlung Tsangpo River negotiates through a 2700 bend just before it enters India. The bend has a total length of about 260km.
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The implications on the downstream areas due to the project depend on how China plans to develop the project. Given China’s historical reluctance to share data with lower riparian states, details remain unavailable in the public domain. It is doubtful if any downstream country is privy to the actual plans.
Based on the topography and head available, it is unlikely to be a single-step generation plan in this project. The huge head is difficult to handle in a single step. Further, other technical issues, such as the lack of a favourable surge shaft location near the Indo-China border, adits for the Head race tunnels etc. in case of a single-step generation, etc., would favour a multi-stage generation. Therefore, a combination of a high storage dam at the start, several small dams downstream and multiple powerhouses appear to be the most reasonable option for optimum utilisation of its available potential in this project. But with China, nothing can be fully ruled out.
Addressing the apprehensions:
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- Water Diversion: Once electricity is produced by taking Tsanpo water down from an elevation of about 2900m at the start of the Great Bend to an elevation of about 600m near the Indian border, the same water cannot be diverted back to China. This will involve pumping it back to an even higher elevation and will involve the requirement of more electricity than produced. Another aspect is the huge head available in the project. The power produced by a unit volume of water in this project is very high. For example, the same volume of water in this project will produce about 10 times more electricity than in the Bhakra project. From a purely economic sense, it is unlikely that China will divert the normal flow of the Tsangpo because of the high premium every unit of water has in this project. However, they may still divert excess flow beyond the capacity of their generating units which they otherwise have to spill during a flood wave. To utilize this, they need to have sufficient storage in their reservoir to absorb the peak flood flow volume, store it and divert it gradually from a point even before the Great Bend. If this is done, we have no reason to complain as floods will be moderated and only excess flood water will be diverted.
- Weaponize the project: Concerns have been raised regarding the potential use of the project as a strategic weapon through the sudden release of large volumes of water during a possible armed conflict between India and China. If the project is developed in multiple steps, such possibility diminishes to a great extent. This is because water has to be released from the large upstream reservoir and it will first cause damage to China’s downstream infrastructure in a multi-step dam system. Further, in modern warfare, there are options for more deadly and effective weapons. China, known for its technological advances, is not likely to use a 20th-century strategy to fight a war with India which may not even be effective today.
- Remaining Concerns: Except for some South American countries where a major part of their electricity comes from hydel projects, hydroelectricity is mostly used today for peak hour generation worldwide. This project is also expected to be used for peak hour generation, especially during the lean period. Therefore, the issue of large variation in flow within the day is expected from across the border during the lean period. We can expect a minimum e-flow by China as it is not in their interest. These will have an adverse impact on the aquatic habitat of the river in Arunachal Pradesh. Further, the likely construction of a large reservoir will trap silt, reducing the river’s natural sediment flow and impacting soil fertility in Assam.
Other concerns arise from the geology of the area. The region is one of the most ecologically fragile and earthquake-prone areas in the world. A large dam in this zone increases the risk of catastrophic events. China’s reluctance to cooperate with lower riparian states like India and share data and information is a serious concern. Similar concerns have been observed in the Mekong River basin, where China’s 12 large dams have negatively impacted downstream nations.
The way forward: India has to make a serious effort and get detailed information on the project proposal. It has to engage China diplomatically to minimize the harmful impacts of the project. There is an urgency, and the matter needs immediate action. This is because China may start the construction of the project, and if delayed, it may be a case of fait-accompli. India also needs to take countermeasures such as the creation of a large reservoir on the Siang River in Arunachal Pradesh to stabilize unequal releases by China expeditiously.