Climate change and over-tapped waterways may leave developing countries in Asia, such as India and China, without enough water to cool power plants in the near future, according to a study.
The study, published in the journal Energy and Environment Science, found that existing and planned power plants that burn coal for energy could be vulnerable.
"One of the impacts of climate change is that the weather is changing, which leads to more extreme events -- more torrential downpours and more droughts," said Jeffrey Bielicki, an associate professor at The Ohio State University in the US.
"The power plants -- coal, nuclear and natural gas power plants -- require water for cooling, so when you don't have the rain, you don't have the stream flow, you can't cool the power plant," Bielicki said.
That is already a problem for some power plants in the US, where extreme weather patterns, which are increasingly frequent especially in hotter months, have reduced water supplies, he said.
However, the study suggests that it is likely to be an even greater problem in developing parts of Asia -- Mongolia, Southeast Asia and, India and China -- where more than 400 gigawatts of new coal-fired power plant capacity are planned for operation by 2030, researchers said.
They found that the increasing power production will itself be part of the problem, creating greater demand for water at the same time that climate change significantly limits the supply.
"Capacity expansion and climate change combined is going to reduce the water available to cool power plants," said Yaoping Wang, lead author of the study and a former doctoral student at Ohio State.
Cooling is critical to a plant's ability to operate --without it, machinery can overheat, causing a shutdown that could disrupt the flow of electricity to homes and businesses, and creating the potential for additional pollution.
The researchers analysed databases of existing and planned coal-fired power plants, and combined that information with high-resolution hydrological maps to evaluate the possible strain on water supplies throughout the region.
They applied different climate scenarios -- increases in global temperature of 1.5, 2 and 3 degrees Celsius above pre-industrial levels, increases set out as milestones in the Paris Agreement, a 2016 international accord to address climate change.
The team then considered different cooling systems and potential use of post-combustion CO2 capture equipment, and the water that might be needed to run them.
The numbers showed that there simply would not be enough water to cool all the power plants, but there is also a lot of local variability, Wang said.
She said the takeaway for agencies that plan and permit plants across developing Asia is that they must evaluate the renewable water available near each power plant, taking into account water use by other plants.
Bielicki said this may require difficult decisions like reducing the number of planned power plants.