Europe does have rain, but the water is not retained

2023-05-06 15:59:00

When you think of drought, you quickly think of a lack of rain. But that open door is hardly open in Europe this year. “Precipitation is somewhat less towards the south, but not enormously,” says Ryan Teuling of Wageningen University. He is involved in hydrology and quantitative water management. So the water is there, but it doesn’t stop the drought. Four factors play a major, and growing, role in this.

Northern Europe is also experiencing this. “These are mechanisms that we will encounter more often in the coming decades,” says Teuling.

1. Evaporation is much faster

The warmer the air, the easier water evaporates from the soil. But that relationship is not one-to-one, it is increasing exponentially. So if it is 1 degree warmer than usual in the already warmer Spain, this will lead to much more extra evaporation than 1 degree extra heat does in the Netherlands. Such a magnified effect is now occurring in the south of Europe. It is already above 40 degrees in parts of Spain, and the moisture present in the soil is evaporating at a rate that we previously only saw in high summer.

2. Snow becomes rain

The warmth of the air determines the precipitation: will it rain or snow? That has a tipping point, an increase from -4 to -3 degrees Celsius makes little difference, which produces snow in both cases. But at some point, a small increase in temperature can suddenly mean that there is no snow at all. And snow has an incredibly important property: it remains for a while before melting and therefore also becomes available as water later in lower areas. In addition, snow reflects sunlight, slowing down evaporation. Winter rain instead of snow in the Spanish Sierras therefore means that the water has already been largely drained by the rivers in winter and has also evaporated extra quickly, resulting in a dry spring.

3. A dry soil does not cool the air

Everything influences each other, and that creates the notorious ‘feedback effects’ that sometimes make climate change so fast. If evaporation causes a drier soil, less and less evaporation will occur, so that the air can be cooled less. We are used to the fact that the hot dry air from above the Sahara starts to cool down through evaporation as soon as it reaches Europe. But that doesn’t happen with a dry soil. “Those extreme temperatures are rising further and further north,” Teuling explains. “At a certain point they will also cross the Pyrenees.”

4. People are becoming more dependent on water

And then there is the factor of human action. We get used to a certain amount of available water and organize our lives accordingly. Teuling cites a dam as an example. “We quickly see this as a solution for a water shortage. We will use that available water and become dependent on it. Then you will have nothing left if there is a real drought.”