When you think of drought, you soon think of lack of rain. But that open door is barely open in Europe this year. “Precipitation is somewhat less towards the south, but not massive,” 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 witnessing this. “These are mechanisms that we will encounter a lot in the coming decades,” says Tulling.
1. Evaporation is much faster
The warmer the air, the more easily water evaporates from the soil. But this relationship is not a one-to-one relationship, rather it is steadily increasing. So if the temperature is one degree higher than normal in already warmer Spain, it will lead to much more additional evaporation than the one degree excess heat in the Netherlands. Such an amplified effect is now happening in southern Europe. It is already above 40 degrees in parts of Spain, and the moisture in the soil is evaporating at a rate previously seen only in the height of summer.
2. The snow turns into rain
The amount of precipitation is determined by the warmth of the air: will it rain or snow? This has a tipping point, the increase from -4 to -3C doesn’t make much difference, which results in snow either way. But at some point, a slight increase in temperature can suddenly mean no snow at all. And snow has a very important property: it stays for a while before it melts, and thus also becomes available as water later in the lowlands. In addition, snow reflects sunlight, which slows evaporation. Thus, winter rains instead of snow in the Spanish Sierras meant that water was already largely drained by rivers in the winter and also evaporated more quickly, drying out the spring.
3. Dry soil does not cool the air
Everything affects each other, and this creates the notorious “feedback effects” that make climate change sometimes very fast. If evaporation causes drier soil, less and less evaporation will occur, so that less air can be cooled. We are used to the fact that hot dry air from above the Sahara begins to cool through evaporation as soon as it reaches Europe. But this does not happen with dry soil. “Extreme temperatures are rising more and more north,” Tulling explains. “At a certain point they will cross the Pyrenees as well.”
4. People are becoming more dependent on water
Then there is the human factor. We get used to a certain amount of available water and regulate our lives accordingly. Teuling cites the dam as an example. We soon see this as a solution to the 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.
Spanish spring is already summer
Now that the spring is already hot, the authorities fear it might be there Serious water problems.
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