China’s decision to build the world’s largest hydropower dam on a river that flows into India and Bangladesh has sparked concerns in both countries over the project’s potential impact on millions living downstream.

Beijing last month approved the super dam’s construction — a new potential flashpoint between India and Beijing — on the lower reaches of the Yarlung Zangbo River in Tibet, which is known as the Brahmaputra River in India. The river plunges some 2,000 meters (6,560 feet) along a section called the “Great Bend” before entering India, offering huge potential to generate power.

China’s Xinhua news agency describes the development as “a safe project that prioritizes ecological protection” and says it would play a major role in meeting the country’s carbon neutrality goals.

But environmentalists in India have flagged concerns about the mega-project in an ecologically sensitive, mountainous region. They say harnessing the river could affect water flow in the country’s northeastern states and Bangladesh.

According to estimates, the planned project would dwarf China’s Three Gorges Dam — the world’s largest — and generate 300 billion kilowatt-hours of electricity annually.

India is urging China to ensure interests of downstream states aren’t harmed by activities upstream. “We will continue to monitor and take necessary measures to protect our interests," Indian foreign ministry spokesman Randhir Jaiswal said last week.

Defending its plans, China says the decision to build the dam was made after rigorous scientific evaluation. “The project will not have a negative impact on the ecological environment, geological conditions and the rights and interests related to water resources of downstream countries,” Chinese foreign ministry spokesperson Guo Jiakun said earlier this week in response to India’s concerns.

Experts in India and Bangladesh, however, are raising questions about the project. “The region proposed for dam construction is highly susceptible to landslides and is located on a geological fault line that intersects the Yarlung Zangbo,” said Y. Nithiyanandam, head of the Geospatial Research Programme at the Bengaluru-based Takshashila Institution.

“Planning a dam of this magnitude in such complex terrain poses significant risks to downstream regions of India and Bangladesh, especially in the event of a mishap or if there is alteration in the water flow.”

The recent earthquake in Tibet that killed at least 126 people has highlighted the region’s vulnerability to such natural disasters, he said. “This is a critical reminder to reassess the proposal for building a mega-dam in such an environment.”

The proposed project’s proximity to a heavily militarized border along India’s northeastern Arunachal Pradesh state, which Beijing has renamed “South Tibet” and claims as its own, is another point of concern.

Relations between India and China witnessed a thaw last October after both sides withdrew troops from two contested border areas. But analysts say a lingering mistrust underlies the project.

“The Indian government is on alert,” Indian Defense Minister Rajnath Singh said Tuesday when asked about the Chinese project, according to the Press Trust of India.

Indian foreign ministry spokesman Jaiswal said New Delhi had reiterated the need “for transparency and consultation with downstream countries.”

Some analysts say China’s failure to share details, such as environmental impact assessments about the project, exacerbate concerns.

“China acts unilaterally on issues related to trans-boundary rivers that originate in their territory. India, for example, has a treaty with Pakistan for common rivers that flow in both countries,” said Srikanth Kondapalli, professor of Chinese Studies at Jawaharlal Nehru University. “There are also questions as to why a dam is being built in a fragile area so close to an area that is contested between the two countries.”

Other analysts point to dams along the Mekong River, which flows from China into Southeast Asia. The dams have led to water scarcity in downstream countries, a fact that Beijing denies.

“When the river crosses two or three countries, it becomes important for them to have a joint look at the project and come to a joint conclusion about how it is to be managed,” said Brigadier Arun Sahgal, senior fellow at the Delhi Policy Group. “It is especially important because, in this case, having a dam so close to the border creates a mutual vulnerability for both India and for China.”

India has also planned a dam on the Brahmaputra River that it hopes will help offset the impact of China’s hydropower project. “The Siang dam will be our counter to the Chinese mega-dam. This is a matter of national security,” Arunachal Pradesh Deputy Chief Minister Chowna Mein told reporters on Monday.

China’s planned super dam has also raised worries in Bangladesh — where the river flows beyond India — that tens of thousands living along riverbanks could be affected if downstream flow is reduced.

“There would be a huge negative impact in Bangladesh,” said Malik Fida Khan, executive director of the Center for Environmental and Geographic Information Services in Dhaka.

“If there is an obstruction in the flow of the river, it could create water scarcity as well as the flow of nutrient-rich sediment, creating an ecological imbalance,” he said. “Riverbank erosion could increase, and this will impact the lives of marginal communities as well as other economic activities in the area.”