Rains from the plains

The classic concept that water evaporates from the seas and returns to the land as rain or snow is only part of the picture.
On average 40% of the rain originates in evaporation from land elsewhere.

This is what hydrologist Dr. Ruud van der Ent found out in his PhD research at the faculty of Civil Engineering and Geosciences. He is the first to have quantified what part of the precipitation comes from water evaporated from land elsewhere on a global scale. After graduating on moisture recycling in 2009, he started his PhD research on a NWO grant in 2011. He then also won the 2011 award from the World Meteorological Organisation.

His study shows for example how rivers in Uruguay depend for up to 70% on the water from the Amazon, 2,000 kilometres north. Or how much of the evaporation in East-Africa returns a week later as rain in West-Africa.

These interdependencies imply that conversion from forest to agricultural land can lead to less rain downwind. But it also means that water conservation techniques could have a positive effect on the rainfall and thus on the water resources of the continent. Either way, the work, says Van der Ent, provides an important context to future studies into the impact of land-use changes.

Ruud van der Ent, A new view on the hydrological cycle over continents, 2 September 2014, PhD thesis supervisor Prof. Huub Savenije (CEGS).

Editor Redactie

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