The Power of Rivers at Risk: Mapping rising threats to hydropower dams using WWF’s Water Risk Filter
By Ariane Laporte-Bisquit, WWF Water Risk Filter Lead & Rafael Camargo, WWF Water Risk Filter Technical Officer
This year’s COP25 kicked off with a stark warning from the UN Secretary General that the “point of no return is no longer over the horizon, it is in sight and hurtling towards us.” The global climate crisis is not a distant threat; climate change is already impacting us and it is primarily being felt through water.
Hydropower has long been regarded as a key part of the solution to climate change, but many existing and planned hydropower projects now face rising risks from the impacts of climate change. Zambia, for example, might soon have to switch off the Kariba hydropower plant for the first time ever as water levels continue to drop. And we found that almost a third of future dams will face increased drought risk (Figure 1). Meanwhile, the renewable revolution means that the world can now prioritize investment in sustainable alternatives, such as wind and solar, and still meet global climate and energy goals — avoiding the need for new hydropower dams on free-flowing rivers.
As highlighted in a recent study in Nature, nearly two thirds of the world’s longest rivers can no longer be considered free flowing, with hydropower dams being a primary cause. By impacting rivers’ flow, connectivity and habitat, dams are one of the major factors behind the 83% collapse in freshwater species populations since 1970 as reported in WWF’s Living Planet Report 2018. They have also contributed to undermining the diverse benefits that healthy, free-flowing rivers provide our societies and economies, including their critical role in climate adaptation. Yet an additional 3,700 hydropower dams are currently under construction or are at some stage of the planning process, according to Global Dam Watch’s Future Hydropower Reservoirs and Dams (FHReD) database.
We used WWF’s Water Risk Filter and Global Dam Watch’s database (FHReD) to quantify how many of these under-construction or potential hydropower dams are in river basins with a range of current or future risks, including risks to hydropower operations from projected increases in frequency or severity of droughts and/or floods due to climate change, and the risk that dams will negatively impact free-flowing rivers and freshwater biodiversity.
So, what did our analysis uncover?
Future hydropower dams face increasing drought & flood risks under climate change
Hydropower dams are generally planned to be built in water abundant regions, but due to climate change, many of these dams are likely to confront increasing drought risk which may negatively impact their ability to generate electricity or provide other services.
Based on the WWF Water Risk Filter’s climate change projection data (under a 2 degrees climate scenario for 2050 developed by the Potsdam Institute for Climate Impact Research), 31% of future hydropower dams will face increased drought risk as illustrated in Figure 1. More frequent and extreme droughts will have substantial financial impacts in countries where hydropower contributes a significant proportion of the energy mix.
Countries with a high reliance on hydropower can suffer from electricity shortages during droughts, as has been happening in Cambodia and Zambia, with widespread impacts on businesses and people. Even in countries that don’t suffer from blackouts, droughts can lead to higher electricity prices for companies and people.
Another important water risk to hydropower operations that should not be neglected is flooding. The WWF Water Risk Filter’s climate change projection data highlights that projected hydropower expansion in certain parts of the world will face increased flood risk, especially for those located in South East Asia, Peru, Ecuador, and along the Nile River (see Figure 2). With climate change, more extreme flood events will increase erosion rates across river basins and thus can increase the siltation of reservoirs behind dams. Further, if dams do not account for potential increases in flood magnitude then they risk being under-designed for resisting floods and at higher risk for dam failure, potentially causing catastrophic social and environmental impacts.
The partial collapse of a hydropower dam that was under construction in Laos in 2018 shows how devastating dam failures can be: it left at least 40 people dead (though estimates range upwards of 1,000 deaths) and nearly 7,000 people were displaced by widespread downstream flooding.
The recent IPCC report on Oceans and Cryosphere also made it clear that retreating glaciers and loss of snow cover in the world’s high mountains would affect run off and river flows, which would impact hydropower generation. According to a study by Vergara et al. (2007), loss of glaciers could cost Peru up to US$212 million in relation to hydropower generation.
Freshwater biodiversity and rivers are under threat from future hydropower dams
A key — and seriously worrying — finding of our analysis is that approximately 75% of projected hydropower expansion will occur within river basins with high freshwater biodiversity richness (based on Freshwater Ecoregions of the World, 2015). More alarmingly, dams are planned on many of the world’s remaining free flowing rivers. If built, they would have a major negative impact on freshwater biodiversity.
More specifically, over 220 dams, with a combined capacity of 98 GW, are under construction or in the planning process within the Amazon Basin — the largest and most biodiverse river basin in the world. Meanwhile from the Ganges to the Mekong and Yangtze, Asia’s most iconic rivers are already heavily dammed, and their remaining free-flowing tributaries are under threat of future dam construction.
The world is currently facing both a climate emergency and a biodiversity crisis. Choosing hydropower dams that speed up the loss of nature will only undermine efforts to reverse the trend, which is critical to a sustainable future for our societies and economies.
From risks and threats to opportunities
Clearly, the planning of any hydropower dam should anticipate these diverse risks, including current risks to biodiversity and free-flowing rivers and future rising risks of drought and/or floods due to climate change.
Furthermore, the renewable revolution offers great potential for future power systems to have far lower negative impacts on environmental and social resources and to be more resilient to climate change. Published in May 2019, the WWF/TNC report, Connected and Flowing, highlights that the price of wind, solar and battery storage have massively decreased whilst the technologies have made great progress. This report used grid expansion models to demonstrate that future power systems can be simultaneously low carbon, low cost and low conflict with communities, rivers and other environmental resources (LowCx3) by deploying a strategically designed mix of solar, wind, storage, and low-impact hydropower.
This diversified energy mix can meet global climate and energy goals, will have greater resilience to floods and droughts and can support sustainable development without sacrificing the last remaining free flowing rivers — and all the diverse benefits they provide people and nature.
