Global groundwater temperatures predicted to rise up by 3.5°C by 2100

Groundwater Warming Threatens Global Water Safety

Groundwater temperatures are projected to rise by 2 to 3.5 degrees Celsius before the end of this century, presenting significant risks to water quality and safety, and threatening ecosystems that depend on this vital resource, according to new research. The study, which is the first to create a global model for groundwater temperature, has predicted the most significant warming in Central Russia, Northern China, parts of North America, and the Amazon rainforest in South America.

Researchers from the Karlsruhe Institute of Technology in Germany led the study. They highlighted that while much of the focus on climate change has been on weather events and water availability, it is equally important to consider its impact on groundwater, which is crucial for life on Earth. Warming groundwater can adversely affect ecosystems that rely on it.

“Rivers rely on groundwater to keep flowing during dry times. Warm waters hold less dissolved oxygen,” explained Gabriel Rau, a study co-author from the University of Newcastle in the UK.

The model estimates that by 2100, between 60 and 600 million people worldwide could be living in areas where groundwater temperatures exceed the highest drinking water temperature guidelines set by any country. According to the World Health Organization, currently only 18 out of 125 countries have temperature guidelines for drinking water.

Warmer groundwater raises the risk of disease-causing microbial growth, thereby affecting drinking water quality and then the lives of people, said Rau. “This is especially concerning in areas where access to clean drinking water is already limited, and in areas where groundwater is consumed without treatment,” he added.

Based on how heat spreads in water, the researchers modelled current groundwater temperatures and projected changes from 2000 to 2100 globally. Groundwater is found beneath the Earth’s surface in the pore spaces of rocks and soils.

“We show that groundwater at the depth of the water table (excluding permafrost regions) is conservatively projected to warm on average by 2.1 degrees Celsius between 2000 and 2100 under a medium emissions scenario,” the authors wrote in the study published in the journal Nature Geoscience.

However, the model showcased that under a high-emissions scenario, driven by fossil fuel development, groundwater temperatures could rise by up to 3.5 degrees Celsius.

The warming of groundwater is cause for concern, depending on whether the issue of climate change can be minimised by reducing greenhouse gas emissions, the researchers said. Warmer groundwater can impact water quality by affecting its chemistry and microbiology, they noted.

“If temperatures increase, we may see significant impacts on our local aquatic animals, including their spawning processes, which will impact industries and communities that rely on these ecosystems,” said Dylan Irvine, a co-author from Charles Darwin University in Australia.

The warming of groundwater not only impacts aquatic life but also threatens human health and water security. Groundwater serves as a crucial source of drinking water for millions of people around the world. The study’s findings suggest that rising groundwater temperatures could make the existing water quality issues worse, making it even more challenging to provide safe drinking water in many regions.

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