Europe has rain, but the water is not retained

When we think of drought, we quickly think of the lack of rain. But this open door is barely open in Europe this year. “Precipitation is a bit less to the south, but not hugely,” 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.

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 more easily water evaporates from the ground. But this relationship is not unequivocal, it increases exponentially. So if it’s 1 degree hotter than usual in the already warmer Spain, that will cause much more extra evaporation than an extra degree of heat in the Netherlands. Such an amplified effect is now occurring in southern Europe. It’s already over 40 degrees in parts of Spain, and the moisture in the ground is evaporating at a rate we’ve only seen before in the height of summer.

2. Snow becomes rain

The heat of the air determines the precipitation: will it rain or snow? This has a tipping point, an increase of -4 to -3 degrees Celsius makes little difference, which produces snow either way. 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 stays for a while before it melts and therefore also becomes available later as water in lower areas. In addition, snow reflects sunlight, which slows 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 very quickly, resulting in a dry spring.

3. Dry ground does not cool the air

Everything influences each other, which creates the famous “feedback effects” that sometimes accelerate climate change. If evaporation causes drier soil, less and less evaporation will occur, so the air can be cooled less. We are used to the fact that the hot, dry air over the Sahara begins to cool by evaporation as soon as it reaches Europe. But this does not happen with dry soil. “These extreme temperatures are increasing further and further north,” says Teuling. “At some point they will also cross the Pyrenees.”

4. People are becoming increasingly 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 it as a solution to a water shortage. We will use this available water and become dependent on it. So you won’t have anything if there’s a real drought.

null Image Bart Friso

Image Bart Friso

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