Research suggests climate change is increasing groundwater temperatures.

A recent global groundwater temperature model indicates that shallow groundwater is set to warm by 2.1 to 3.5°C on average by the end of the century, raising significant concerns about the future of ecosystems, water quality, and human health. 

The model, a collaborative effort involving researchers from Charles Darwin University (CDU), the University of Newcastle, Canada, Germany, and Austria, underscores the widespread impact of climate change on groundwater resources.

“Groundwater is the water that is present beneath the Earth’s surface in pore spaces in rocks and soils. It is critical for life on earth,” CDU researcher Dr Dylan Irvine says.

Increased groundwater temperatures could threaten temperature-sensitive ecosystems dependent on groundwater.

The model projects the highest warming rates in Central Russia, Northern China, parts of North America, and the Amazon rainforest, with Australian groundwater temperatures also expected to rise. 

By 2099, an estimated 59 to 588 million people worldwide could be living in areas where groundwater temperatures exceed the highest drinking water temperature guidelines currently set by any country.

Dr Gabriel Rau, a hydrogeology lecturer from the University of Newcastle, warned that warming groundwater temperatures could adversely affect many ecosystems reliant on groundwater. 

“Rivers rely on groundwater to keep flowing during dry times. Warm waters hold less dissolved oxygen. We’ve seen in the Murray Darling how low oxygen in water can contribute to fish deaths,” Dr Rau noted.

The implications for water quality are also severe. 

According to the World Health Organisation, only 18 out of 125 countries currently have temperature guidelines for drinking water. 

“As groundwater warms, there is increased risk of pathogen growth which impacts drinking water quality - potentially affecting the lives of many people,” Dr Rau says. 

This is particularly concerning for areas with already limited access to clean drinking water and where groundwater is consumed without treatment.

Economic impacts are another significant concern. 

Industries such as agriculture, manufacturing, and energy production heavily rely on groundwater. 

If groundwater becomes too warm or contaminated, it could disrupt operations and lead to economic losses.

To illustrate the potential change in groundwater temperatures due to climate change, the research team, led by Dr Susanne Benz from the Karlsruhe Institute of Technology, has developed an interactive online application to show the projected temperature changes.

The Google Earth Engine app provides zoomable maps of annual mean, maximum and minimum groundwater temperatures at different depths and seasonal variability for selected years and climate scenarios, that the team hopes will facilitate further research.

The research paper titled ‘Global groundwater warming due to climate change’ has been published in the journal Nature Geoscience.