Water crisis due to climate change: More serious than previously thought

Until now, projections of climate impact on river flows were typically calculated using physical models, such as those reported by the IPCC (Intergovernmental Panel on Climate Change).

A study published in the journal Nature Water analyzed data from more than 9,500 river basins around the world, finding that climate change could lead to much more serious local water crises than previously thought.

Researchers in Austria, the United States, China, Australia and Saudi Arabia compared data from that number of basins and found that the connection between rainfall and the amount of water in rivers is more sensitive than previously anticipated by science.

Research published in Nature Water found that future water supply crises would be more severe than predicted by climate change models so far. The regions most affected by 2050 would be Africa, Australia and North America.

The study focused on how climate change will affect water supplies. "We show that global current flow in the near future (2021-2050) may be lower than predicted by Earth system models," the research notes.

The decrease in streamflow is due to smaller contributions from rainfall and greater sensitivity of streamflow to changes in evapotranspiration. The regions where the supply would be most affected in 2050 would be Africa, Australia and North America.

Model approach and measured data approach

Günter Blöschl, the lead author of the research, told Phys.org that “we looked 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."

According to Blöschl, “Until now, runoff measurements have generally not been included in models at all, such as those currently reported by the IPCC. With the series of measurements now available, it should be possible to fit the physical prediction models."

But no global conclusions can be drawn from such individual observations: "The way in which the water balance depends on external parameters varies from place to place; the local vegetation also plays a very important role here," says Günter Blöschl. It is difficult to develop a simple physical model that can be used to calculate these interrelationships in all parts of the world with precision.

Therefore, Günter Blöschl has collaborated with colleagues from China, Australia, the USA and Saudi Arabia to build and analyze a large database of flow observations from around the world. More than 9,500 basins were included, with time series extending several decades into the past.

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

Günter Blöschl, Professor, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology.

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