Newswise – As the world’s largest unfrozen freshwater resource, groundwater is vital to life on Earth. Researchers at the Karlsruhe Institute of Technology (KIT) have investigated how global warming is affecting groundwater temperatures and what this means for humanity and the environment. Their study indicates that by 2100, more than 75 million people are likely to live in areas where groundwater temperatures exceed the highest limits set for drinking water by any country. their results have been published nature geology, (DOI: 10.1038/s41561-024-01453-x)
The Earth’s climate system is warming due to increasing concentrations of greenhouse gases in the atmosphere, which limit the amount of heat that can be emitted. The oceans absorb a large portion of this heat, but soil and groundwater also act as heat sinks. However, little is yet known about the effects of Earth’s surface warming on groundwater over space and time. “To bridge this gap, we have simulated projected changes in global groundwater temperature by 2100,” said Dr. Suzanne Benz of the Institute for Photogrammetry and Remote Sensing at KIT, who led the study in collaboration with Dr. Kathrin Meinberg and Professor Philip Have prepared. Blum from the Institute of Applied Geosciences at KIT. “We can provide maps showing global groundwater temperatures at different depths beneath the Earth’s surface. The maps show that the world’s highest groundwater warming rates can be expected in places with shallow groundwater levels and/or high atmospheric temperatures.
The researchers based their projections on SSP 2-4.5 and SSP 5-8.5 climate scenarios. These scenarios reflect different socio-economic development pathways and different trends in atmospheric greenhouse gas concentrations in the future. SSP 2–4.5 is in the middle range of potential future greenhouse gas concentration trends; SSP is 5-8.5 in the upper extreme.
Millions of people affected by extremely hot drinking water
The study indicates that by 2100, groundwater temperatures will rise by 2.1 °C in the SSP 2-4.5 scenario and by 3.5 °C in the SSP 5-8.5 scenario. “Already about 30 million people live in areas where groundwater is warmer than the limits set in strict drinking water guidelines. This means that without treatment the water there may not be safe to drink. For example, it may need to be boiled first. Due to the heat in the ground, drinking water also becomes hot in the water pipes,” Benz said. “Depending on the scenario, several hundred million people could be affected by 2100.” According to the study, the figure would be 77 to 188 million for SSP 2-4.5 and 59 to 588 million for SSP 5-8.5. The wide ranges are due to spatial variations in climate change and population trends. Researchers project the lowest warming rates in mountainous regions with deep water tables, such as the Andes and Rocky Mountains.
Temperature change affects the ecosystem
Groundwater temperature plays an important role in water quality by influencing many chemical, biological, and physical processes. “Under certain circumstances, rising groundwater temperatures may increase concentrations of harmful substances such as arsenic or manganese. These high concentrations can have negative effects on human health, especially when groundwater is used as drinking water,” Benz said, adding that warm groundwater is critical for groundwater-dependent ecosystems, aquatic biogeochemical processes, geothermal energy potential and Also affects the thermal regime in rivers. It may also pose a challenge to biodiversity and a threat to carbon and nutrient cycles.
Another impact of increased near-surface and groundwater temperatures is that critical limits in water distribution networks may be exceeded. This may have effects on human health, for example by promoting the growth of pathogens Legionella spp, Fish species, especially salmon, are also affected by changing conditions. If groundwater-dependent breeding sites in rivers become too warm, their reproduction may be in danger. “Our results show how important it is to take action to protect groundwater and find sustainable solutions to combat the negative impacts of climate change on groundwater,” Benz said.
original publication
Suzanne A. Benz, Dylan J. Irwin, Gabriel C. Rau, Peter Bayer, Kathryn Menenberg, Philipp Blum, Rob C. Jamieson, Christian Griebler, Barrett L. Kurilik: Global groundwater warming. Nature Geology, 2024. DOI: 10.1038/s41561-024-01453-x,
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