Posted on February, 24 2022

Climate change will dramatically increase the frequency of floods and droughts on the rivers where hydropower projects operate around the world, increasing risks both to their safety and capacity to generate electricity, according to a new study  in the Journal Water.

Using the publicly available WWF Water Risk Filter tool, the study found that 61 percent of current and projected hydropower dams will be in river basins with high to extreme risk of water scarcity, floods, or both by 2050.

“Hydropower projects have long been regarded as low risk renewable energy investments but risks from floods and droughts are projected to increase dramatically in many river basins due to climate change – likely creating increasingly challenging operating conditions for many hydropower projects,” said Jeff Opperman, WWF Global Lead Freshwater Scientist and lead author on the study.

“Already, hydropower generation has declined due to falling water levels in some regions, such as the southwestern US, southern Africa, and Brazil, while we’ve also seen dams fail because of floods,” added Opperman.

The study found that 32 percent of existing and 20 percent of projected hydropower dams are in river basins projected to have higher water scarcity risk by 2050, especially in eastern China, the Middle East, Morocco, the southwestern USA, and India.

The number of hydropower dams located in basins with the highest levels of flood risk will increase from 4 percent to 20 percent by 2050. However, the shift will be even more dramatic for dams that are planned or under construction with the total rising from 2 percent to 40 percent, especially in Myanmar, Peru, Hubei region of China, Kenya, Uganda, Ecuador and Cameroon.

“Hydropower developers, investors and governments must focus more on the projected changes in rainfall patterns, river flows and extreme events in their planning and operations as these will lead to increased risks for hydropower in many river basins across the world,” said Rafael Camargo, WWF’s Water Risk Filter Technical Lead and an author on the study.

“Future dams are generally planned based on historic hydrology but the Water Risk Filter analysis shows that this is an increasingly risky approach thanks to climate change: decisions about whether to build a dam should include a comprehensive understanding of risk - including how risks are likely to shift in coming decades,” added Camargo.

The study also highlights the serious threat posed by planned hydropower to freshwater biodiversity. Fragmentation of rivers by dams is one of the leading causes of the 84 percent collapse in freshwater species populations on average since 1970. Yet the analysis found that up to 80 percent of all planned dams are in areas with high or very high risk to freshwater biodiversity, such as the Amazon, Irrawaddy, Mekong and river basins across the Balkans.

“The risk to rivers and biodiversity has to be a critical factor in decisions on future dams because poorly planned hydropower has already contributed to the loss of species and negatively impacted freshwater fisheries that millions of people depend on for food,” said Opperman.

“Importantly, countries now have a choice: the cost of wind and solar has dropped so quickly that hydropower is no longer the only renewable option. Instead, countries can now invest in power grids that are LowCx3 – low carbon, low cost and low conflict with rivers and communities,” added Opperman.

This new study provides several recommendations for how hydropower planners and managers can reduce risks from climate change and environmental impacts.

For example, investing in Nature-based Solutions, such as restoration of forests and wetlands - both upstream and downstream of dams - can help reduce flood risks. In addition, the licenses granted to hydropower projects can be required to be periodically renewed, as they are in the US. The license renewal process provides an opportunity to reassess how projects are operated after accounting for new information on hydrological risks, likely shifts in climate, and conditions of environmental resources.