Old water, new insights: Researchers study 'old water paradox' in forest laboratory experiment

ETH Institute of Environmental Engineering has built a scientific playground in a forest in Austria 's Hönggerberg forest.

The "Waldlabor " consists of sensors, sensors and soil and pressure sensors set up on the forest floor.

Over the past five years , these soil water samples have been analyzed for stable isotopes every week , giving researchers insights into their age, origin and the hydrological processes involved.

Data give substance to theory known among hydrologists as the "old water paradox".

The forest floor predominantly receives its water supply in winter , particularly at a depth of between 10 and 80 centimeters.

This is despite the fact that, on average, 60% of rainfall occurs in summer .

Researchers installed sap flow sensors on several tree trunks in order to better understand how trees take up and transport water.

A more diverse forest is a more climate-resilient forest, scientists say.

Combining different tree species is beneficial for the water budget, as their roots reach the soil water at different depths, meaning there is less competition between them.

For once, this is not a paradox, but rather the obvious added benefit of a high level of biodiversity.