Pitting hydropower against weather extremes?

Holly Young

Reliable, cheap and low carbon since coming into use over a hundred years ago, hydropower has become a vital clean energy source, today providing more electricity than all other renewables combined. But recent power shortages in Ecuador and Colombia have highlighted its vulnerability in the face of climate change.

A drought fueled by the El Nino weather phenomenon has reduced reservoir water levels in hydropower plants, which both countries rely on for most of their electricity. This has led Ecuador to declare a state of emergency and institute power cuts. In neighboring Colombia, water has been rationed in the capital and the country has halted electricity exports to Ecuador.

Hydropower functions by harnessing the movement of water flowing through a turbine, which generates electricity as it spins.

"Hydropower is dependent on water so clearly if there is no water at all then hydropower cannot be used, disrupting energy production and stressing energy systems," said Matthew McCartney, expert on sustainable water infrastructure with the International Water Management Institute, based in Sri Lanka.

Droughts and sudden floods which can also damage dams made more frequent and severe by climate change, are therefore an "increasing concern" for hydropower, he added.

Hydropower plants are built to respond to changes in the weather storing water in the rainy season to use when it becomes dry, explains Luz Adriana Cuartas, a hydrologist at the Brazilian Center for Monitoring and Early Warning of Natural Disaster.

But Colombia and Ecuador have seen surging temperatures and low rainfall last year, says Cuartas. "And this is why regulation [of hydropower] is becoming more challenging." The problem in the region has been exacerbated by a simultaneous increased demand for energy and water as people turn on air conditioners and taps, she adds.

Ecuador and Colombia are not isolated cases. While hydropower remains the world's largest renewable source of electricity and had been increasing by 70% over the last two decades, in the first half of 2023 its global output saw a historic drop, according to Ember, a UK based energy think tank. Their findings say drought  likely exacerbated by climate change drove an 8.5% drop in hydroelectricity around the world during this period.

China, the world's largest hydroelectricity generator, accounted for three quarters of the global decline. In 2022 and 2023 droughts led to Chinese rivers and reservoirs running dry, causing power shortages and forcing the country to ration electricity.

Just over a quarter of all hydropower dams are in regions that are projected to have medium to extreme risk for water scarcity in 2050, according to one 2022 study.

Countries with a high dependence on hydropower are particularly vulnerable to climate impacts, says Giacomo Falchetta, researcher at the International Institute for Applied Systems Analysis. In Africa, where his research has focused, hydropower accounts for over 80% of electricity generation in the Democratic Republic of Congo, Ethiopia, Malawi, Mozambique, Uganda and Zambia many of which are also struggling with severe droughts.

"On top of that [high dependence], they have limited installed capacity for alternative power generation and limited transmission infrastructure to import power," said Falchetta.

The solution for these countries is to diversify their power sources by incorporating other renewable technologies such as wind and solar into their energy mix, said Falchetta. He highlighted Ghana and Kenya as two countries that are successfully moving from high reliance on hydropower towards a more "robust portfolio of technologies".

Innovations around placing floating solar panels on the water's surface in hydropower plants as countries such China and Brazil are exploring have significant potential, says McCartney. "In some cases, you only need to cover like 15-20% of the reservoir and you can generate as much electricity alone as you do from the hydropower."

Countries like Colombia, Ecuador and others with high hydropower reliance need to work towards an optimum mix of renewables, says Lei Xie, energy policy manager at the International Hydropower Association (IHA). "We say that water, wind and sun get the job done." Despite the climate-risks associated with the technology, it is still considered by many to have a continued role in decarbonizing the global economy.

"I would say that hydropower is a technology that will definitely still be expanded because it allows to provide cheap power at large scale," said Falchetta. Building more medium scale plants, rather than the mega dams of the past, would help mitigate the climate-risks associated with overdependence on one big piece of infrastructure, he explains.

While the International Energy Agency predicts hydropower will eventually be overtaken by wind and solar, they state it will remain the world's largest source of renewable electricity generation into the 2030s. Yet the agency anticipates a significant slowdown in industry growth this decade could jeopardize net-zero ambitions.

Hydropower capacity needs to double by 2050 if the world is to stay on track for limiting global temperature increases to 1.5C, according to the International Renewable Energy Agency.

The IHA estimates this would require a significant increase in investment approximately $130bn annually from now to 2050.

While climate change is going to increase the risks for hydropower, better management of water within a basin and how plants are integrated with other renewables can improve resilience to drought, says McCartney.

Hydropower is also needed to stabilize electricity generation, providing power when wind and solar can't, he adds. "Hydropower can act as a very large battery, because you can switch it on and off very quickly," said McCartney. Hydropower plants are usually also able to ramp electricity generation up and down more quickly than coal, nuclear or natural gas.

"Pumped-storage hydropower, which pumps water uphill when electricity is cheap and releases it downhill when electricity is expensive can also help," said McCartney. "These schemes consume relatively little water because it is recycled. They are not totally immune to drought but are more so than traditional hydropower schemes."