One of the most enduring paradoxes in water policy is that large dams are typically portrayed either as indispensable engines of development and climate resilience or as inherently destructive interventions that should be avoided at all costs. Both perspectives contain elements of truth. Both are myths when presented as universal truths.
This paradox matters because large dams are once again at the center of global water debates. Governments, development banks and investors increasingly view them as critical infrastructure for addressing water scarcity, energy demand, food production and climate adaptation. At the same time, environmental groups, civil society organizations and affected communities continue to highlight the profound social and ecological costs associated with large dam projects.
The problem is not large dams per se, but rather the myths that surround them. Better decisions require moving beyond polarized positions and engaging honestly with trade-offs, alternatives, their management and context.
Temples, pyramids and trade-offs
Following the Second World War, large dams became powerful symbols of national development. In India, Prime Minister Nehru famously described dams as the "temples of modern India" while in Egypt, President Assad called the Aswan High Dam the "pyramid of the twentieth century." Inspired in part by the success of the Tennessee Valley Authority in the 1950s, dams were promoted worldwide as engines of economic growth, flood control, irrigation and electricity generation. They became icons of progress.
The Aswan High Dam illustrates both the promise and the pitfalls of this vision. It transformed Egypt's water management, expanded irrigation and generated electricity, but it also displaced more than 100,000 people, altered ecosystems, trapped sediments and accelerated coastal erosion. Its legacy reminds us that large dams often deliver substantial benefits while simultaneously imposing profound and long-lasting social and environmental costs.
Understanding large dam myths
Large dams are often framed as a near-universal solution to water and development challenges. This myth is particularly powerful because it is linked to pressing concerns: droughts, floods, energy insecurity, food production, and both mitigating and adapting to climate change.
The attraction is obvious. Large dams appear to offer a single piece of infrastructure capable of addressing multiple challenges simultaneously. This vision has shaped projects around the world, from Kariba on the Zambezi and China's Three Gorges Dam to India's Narmada Valley projects and Brazil's Belo Monte Dam.
Today, there are approximately 60,000 large dams worldwide, a testament to the enduring influence of this idea.
This large dam myth typically rests on four recurring assumptions: benefits are overestimated, costs and risks are underestimated, alternatives are neglected, and political incentives outweigh evidence. Projected gains from irrigation, hydropower and flood control often fall short of expectations, while environmental degradation, social disruption and economic risks receive insufficient attention. Meanwhile, alternatives such as groundwater storage, wetlands, aquifer recharge and demand management are frequently overlooked. The scale and visibility of dams also make them attractive political symbols that can overshadow more balanced assessments.
The human and environmental toll
The consequences of poorly planned dams have been profound. Millions have been displaced by reservoirs, freshwater ecosystems have been degraded, and rivers fragmented. Some estimates suggest that globally, as many as 500 million people have been adversely affected by dam projects through displacement, livelihood disruption or reduced ecosystem services. These impacts typically fall on poor and marginalized communities.
Growing awareness of these impacts fueled opposition to large dams in the late twentieth century, culminating in the World Commission on Dams report (2000). Yet criticism generated a counter-myth: that all large dams are inherently harmful. This is no more convincing than the claim that dams are always beneficial. Navigating between myth and counter-myth, the critical questions are not whether water storage is needed, but what form it should take, where it should be located, who benefits, and who bears the costs.
Why this debate matters today
The debate has become even more relevant in the 21st century. Today, population growth, urbanization, energy demand and climate change are driving renewed interest in large dams. Yet climate change also makes their performance less predictable as rainfall patterns shift and extreme events become more frequent. Some reservoirs also emit significant quantities of methane, challenging assumptions that hydropower is always climate-friendly.
Large dams do not automatically guarantee water security. They are not always the most economical form of storage. Nor should they be assumed to be universally climate resilient.
Managing diversified water storage and moving beyond myths
The central message is not that large dams are good or bad. It is that simplistic arguments — whether celebratory or oppositional — lead to poor decisions.
Water storage remains essential for development and climate adaptation, but it comes in many forms, including reservoirs, groundwater aquifers, wetlands, floodplains and soil moisture. As water insecurity and climate risks intensify, the challenge is not choosing between dams and no dams. It is choosing the right mix of storage options, in the right places, with appropriate safeguards and governance. Moving beyond the large dam paradox is therefore not about rejecting storage, but about managing it more intelligently, equitably and sustainably.
