A global study has revealed that shallow groundwater temperatures are projected to increase by an average of 2.1 to 3.5 degrees Celsius by the end of this century.

This alarming forecast comes from the world's first global groundwater temperature model, developed by an international team of researchers including Dr. Gabriel Rau from the University of Newcastle and Dr. Dylan Irvine from Charles Darwin University.

The model predicts that the most severe warming will occur in Central Russia, Northern China, parts of North America, and the Amazon rainforest. Australian groundwater temperatures are also expected to rise significantly.

Dr. Irvine emphasises the critical importance of groundwater for life on Earth and warns that increasing temperatures could threaten temperature-sensitive ecosystems dependent on groundwater.

The researchers stress that while much attention has been given to climate change's impact on weather events and water availability, the effects on groundwater must not be overlooked.

The study's findings have far-reaching implications for water quality, ecosystem health, and human safety. Dr. Rau explains that warmer groundwater holds less dissolved oxygen, which could lead to fish deaths in rivers that rely on groundwater during dry periods.

Perhaps most concerning is the potential impact on drinking water safety. The model estimates that by 2099, between 59 and 588 million people worldwide could be living in areas where groundwater temperatures exceed the highest drinking water temperature guidelines set by any country.

This increase in temperature could promote pathogen growth, posing significant risks to human health, especially in regions where access to clean drinking water is already limited.

The warming groundwater also presents economic risks, potentially disrupting industries such as agriculture, manufacturing, and energy production that rely heavily on groundwater resources.

To help visualise these projected changes, the research team has developed an interactive online application using Google Earth Engine. This tool allows users to explore annual mean, maximum, and minimum groundwater temperatures at various depths for different years and climate scenarios.

As the world grapples with the multifaceted challenges of climate change, this study underscores the urgent need for comprehensive strategies to mitigate global warming and its impacts on vital water resources.

The findings have been published in Nature Geoscience.