Future water crisis could be much worse than expected

New research shows that climate change can lead to greater water crises than previously expected. Climate change affects precipitation and evaporation around the world. This impacts the amount of river water that can be used locally. 

The climate impact on streamflow has been estimated using projections from the IPCC (Intergovernmental Panel on Climate Change). Now, a study led by Vienna University of Technology indicates that previous models have underestimated the sensitivity of water availability in a warming climate. 

“In the climatology community, the effects of climate change on the atmosphere are very well understood. However, their local consequences on rivers and the availability of water falls into the field of hydrology,” explained study co-author Professor Günter Blöschl.

Locally, it is often possible to determine how water availability is related to precipitation or temperature. But global conclusions cannot be drawn from individual observations: 

“How the water balance depends on external parameters varies from place to place; local vegetation also plays a very important role here,” said Professor Blöschl. 

It is difficult to develop a model that can calculate these interrelationships at all places in the world.

Professor Blöschl collaborated with colleagues from China, Australia, the United States, and Saudi Arabia to analyze a large database of streamflow observations from 9,500 hydrological catchments around the world. 

“We look at how much the amount of available water changed in the past when external conditions changed. In this way we can find out how sensitively changes in climate parameters are related to a change in local water availability. And this allows us to make predictions for a future, warmer climate,” said Professor Blöschl.

The connection between precipitation and the amount of water in rivers is much more sensitive than current models assume. This demonstrates the need to update or revise models that predict climate impact on water supply. 

“Up to now, runoff measurements have usually not been included at all in the models, such as those currently reported by the IPCC,” said Professor Blöschl. “With the series of measurements now available, it should now be possible to adjust the physical prediction models accordingly.”

The results suggest that climate impacts on the water supply in many parts of the world have been underestimated. This is especially the case for Africa, Australia and North America, where new data predicts a higher risk of water supply crises by 2050.

“The lower streamflow predicted here is due to smaller contributions from precipitation and stronger sensitivity of streamflow to changes in evapotranspiration, which is related to increased radiation energy and vapour transfer, and enhanced vegetation greening,” wrote the study authors. “Our estimate points towards the possibility that a future water crisis could be more severe than anticipated.”

The research is published in the journal Nature Water.

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By Katherine Bucko, Earth.com Staff Writer

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