Water management

What is a precipitationshed?

Patrick Keys explains

Over 500 million people globally live in dry regions and rely solely on rainfall to grow their food. Any changes to this rainfall can have dramatic consequences for their livelihoods.

An increasing amount of research shows that human-caused changes to landscapes can significantly impact the amount of water that is evaporated into the atmosphere.

Centre researcher Patrick Keys has together with researchers from The Netherlands and Germany developed a method to locate the region from which evaporated water starts its travel through the atmosphere, and where it later falls as rain or snow.

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The method is based on a computer model that backwards track the path of the water, from where it falls as rain, back through the atmosphere to its origin as evaporation.

Keys and his colleagues call the evaporation area a precipitationshed. This can be understood as the area upwind of a specific location that contributes to most of the rainfall. In other words, the precipitationshed can be understood as a 'watershed of the sky', where evaporated water flows through the atmosphere to a specific location, falling out as rain.

Stockholm Resilience Centre is a collaboration between Stockholm University and the Beijer Institute of Ecological Economics at the Royal Swedish Academy of Sciences

Stockholm Resilience Centre
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Organisation number: 202100-3062
VAT No: SE202100306201