A warming climate will cause rivers in regions affected by snowfall to discharge significantly less water, or so former Master’s student Wouter Berghuijs (CEG faculty) concludes in Nature Climate Change.
In a warming climate, less precipitation will fall in the form of snow and more in the form of rain. In his graduation research, Berghuijs considered how this would affect the average amount of water flowing through a river. His findings were published last weekend in Nature Climate Change, something that is quite uncommon for a graduation research.
The general believe was that a shift towards less snowfall and more rain has little influence on the average amount of water in rivers. Berghuijs proved this false. After studying historical data on snowfall and on the mean annual stream flow from 420 catchments located across the United States he came to the conclusion that a warmer climate with more rain and less snow can lead to a significant decrease in stream flow.
“A systematic analysis of historical data suggests that, with a rise of two degrees in temperature, the amount of water in the river decreases on average by about ten per cent over a whole year”, says Berghuijs in a TU press release. “This figure does vary widely per river.” The underlying process behind this decrease is not clear yet.
Mechanistic modelling of a catchment in Sweden already suggested that a warmer climate with more rain and less snow can lead to a significant decrease in stream flow. However, until Berghuijs’ research this theory had not yet been substantiated by empirical findings.
With more than one-sixth of the Earth’s population depending on melt water for their water supply and ecosystems that can be sensitive to stream flow alterations, the socio-economic consequences of a reduction in stream flow can be substantial.
Berghuijs is now working on a follow-up research. After graduating from TU Delft in December, he started as a PhD candidate at the University of Bristol (which also contributed to the research in Nature Climate Change). Berghuijs is now studying the effects of temperature change in parts of Scandinavia and the Alps. “This could provide a clear indication of what this phenomenon means for the Netherlands, because you can be sure that a river such as the Rhine will certainly feel the effects of this.”
W.R. Berghuijs et.,al. A precipitation shift from snow towards rain leads to a decrease in streamflow’, Nature Climate Change, 18 May 2014.
http://dx.doi.org/10.1038/nclimate2246
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