Hydropower is the largest source of low-carbon electricity in the world today. And its benefits are needed more than ever. The International Energy Agency estimates that we will need to double the amount of installed hydropower capacity—which stands today at around 1360 gigawatts worldwide—in order to limit the rise in average global temperatures to 1.5 degrees Celsius above pre-industrial levels.

Hydropower has many other advantages. Dams can contribute to climate change adaptation by reducing floods and the impact of droughts on people and agriculture. They can also bolster food and water security and allow navigation where it might not otherwise be possible. For many countries, especially in the Global South, hydropower is essential for energy access and economic growth.

Yet the heavy social and environmental costs of hydropower projects have also earned it some fierce detractors. Dams can alter river flows, affecting how much water reaches users, and when. Their construction and operation sometimes erodes river banks and submerges lands where people live and work. Dams can also disrupt fish migrations, and change sedimentation patterns and navigation routes along a river system.

Downstream communities, in particular, have discovered that dams can reduce the quantity and quality of water available and degrade fisheries, negatively impacting livelihoods and food security. Indeed, researchers have discovered that hydropower generates “the highest number of conflicts with concerns over social and environmental damages” among all low-carbon energy projects.

Given increasing calls for a just and peaceful energy transition, what role should hydropower play in achieving this aim? A troubled history in which past hydropower projects have created disruptions in local and transboundary contexts complicates the issue. Can countries simultaneously ramp up capacity while making sure that hydropower is both just and peaceful?

Meeting Local Challenges

Hydropower dams can destabilize and disrupt the livelihoods of communities and ecosystems along a river system. Often, hydropower projects displace entire communities. During a flurry of large dam construction in the 1980s and 1990s, an estimated 4 million people were displaced annually, according to a World Bank estimate.

Large-scale dam construction has declined since that era, but hydropower projects continue to displace communities around the world. Indigenous people have been particularly hard hit by the negative impacts of hydropower projects. As well as losing livelihoods, they can have their sense of culture and identity associated with a particular place eroded by displacement.

In Brazil, construction of the Belo Monte Dam blocked parts of the Xingu River, a major tributary of the Amazon, and flooded large areas of rainforest. These impacts forced almost 20,000 ribeirinhos—a traditional group who live near rivers and subsist on small-scale farming and fishing—to relocate.

When displaced communities receive any compensation or assistance at all for displacement and other negative impacts, they are often given little say in the form it takes. Frequently, this compensation is inadequate and unsuited to the communities’ traditions or livelihoods. And affected communities may not even enjoy the benefits of the locally produced hydropower, which can both fuel resentment and increase marginalization.

As a result of impacts like these, hydropower projects can fuel protests, violence, and unrest. Incidents of repression against protestors are especially frequent when it comes to hydropower and can often include violence and even assassination of protest leaders.

Transboundary Trials

States tend to cooperate about transboundary water issues, but hydropower dams on shared river systems have nevertheless sometimes sparked tensions. More than 70 per cent of planned or existing hydropower dams are situated within major transboundary river systems. While wars have not yet been fought over water, fears over ‘basins at risk’ in a less predictable world continue to simmer.

Dams constructed in one country can impact local communities in another. For instance, the Yali Falls Dam, the second largest dam in Vietnam, is located on the Sesan River only 80 kilometers upstream of the Cambodian border. After unexpected releases of water from the dam damaged property on the Cambodian side of the border, the two countries established an early warning system. However, other negative impacts of the dam persist, such as decreased fish catches, which many downstream communities in Cambodia depend on for their food supplies and income, and degraded water quality in the river, causing a rise in illness. This case highlights the need to conduct a transboundary impact assessment before any significant dam construction.

Transboundary dams also intertwine with regional dynamics to escalate cross-border tensions. Projects such as the Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile pose challenges to regional security, especially in the absence of a basin-wide water agreement. In February 2022, the GERD became operational despite continued objections by Egypt and Sudan over its downstream effects. Since then, the filling of the dam’s reservoir (the third and final filling was recently completed) and the start of energy production have aggravated transboundary relations, especially in the absence of a trilateral agreement on the dam’s storage and operation. Further regional fallout from this new hydropower system is likely in the years ahead, especially if an agreement is not reached.

The potential for impacts on populations living near a transboundary dam seems certain to increase. It has been estimated that by 2050, a majority of the world’s population will live downstream of a dam reservoir more than 50 years old. Such transboundary conflict risks will only intensify if they are not properly addressed today.

Fulfilling Hydropower’s Positive Potential

These examples of local and transboundary conflicts created by hydropower appear to confirm the arguments of critics. But these conflicts can be avoided if countries include mitigation strategies to tackle associated social and environmental consequences, including risks to peace and security, in their project planning. Sustainable hydropower can even become a source of peace.

For instance, in the right settings, hydropower dams can help conflicted-affected societies meet their populations’ needs for electricity and water when infrastructure has been damaged during conflict. In post-war Nepal, international financiers helped the newly installed national government develop micro-hydropower stations that positively contributed to socio-economic development for rural communities in remote regions. The government’s effort did not strengthen state legitimacy, however, because its leaders failed to communicate the state’s contribution in the project to the nation.

SIPRI’s recent report Environment of Peace: Security in an Era of Risk also offers insights into how best to maximize the benefits of hydropower for peace and development. It not only recommends wider use of environmental and social impact assessments and system-scale planning approaches to anticipate social and environmental risks, but also the establishment of frameworks and implementation procedures to mitigate these risks from the start of any hydropower project.

System-scale hydropower planning can also be combined with planning tools such as strategic environmental assessments (SEAs), which help evaluate the potential social and environmental impacts at a whole-sector scale. The costs and benefits of a hydropower project can then be compared with alternative renewable energy options such as solar and wind.

Assessments of peace and security risks can also be incorporated into SEA exercises. Their inclusion at a strategic level is highly relevant in countries where potential hydropower sites are in conflict regions. The International Finance Corporation spearheaded an SEA of Myanmar’s hydropower sector that included risk assessments of ‘peace and conflict’ in each sub-basin. The sector-wide assessments looked at factors including the presence of armed groups, the frequency of violent clashes, and pre-existing inequalities and grievances.

Where river systems cross borders, transboundary impact assessments are also needed. Transboundary basin organizations and agreements can help establish credibility around the impact assessments and facilitate cooperation among water-sharing governments. Such assessments have been recommended and conducted in important transboundary watersheds including the Mekong, Euphrates-Tigris, and Nile basins.

Hydropower will be a critical element in climate change mitigation and adaptation in the coming decades. But it is imperative that the mistakes of the past are not repeated. Ignoring peace and security considerations will undermine the transition. But done right, hydropower can have sustainability benefits that go far beyond energy access alone.