The simple scientific experiment that explains why it rains a lot after a drought can be dangerous

A twitter thread virus has demonstrated the dangers of torrential rains during times of drought. With the DANA that threatens Spain, a special concern arises for the adverse effects on soil. This simple home experiment was demonstrated by the Dr Rob Thompson from the University of Reading, England. With only a few glasses and different soils, it warns of the danger of rain after drought: flash floods.

DANA refers to the isolated depression at high levels, but is colloquially known as cold drop. It happens when a mass of cold air —in height— collides with a mass of warm air —on the surface. This can cause intense showers and thunderstorms.

the problem itself it’s not that it rains. There are two factors that they must come together; it only takes one dry soil after heat waves —and droughts— and a lot of water in a short time. To demonstrate this, the doctor only used a glass full of water and placed it upside down on the ground to replicate the effects of sudden rain. To compare the effects he used moist grass, normal soil during the summer and one already beaten down by the heat.

The results were immediate. The moist soil absorbed the water without difficulties and in seconds. Normal soil absorbed it with greater difficultyand it cost twice the time achieve absorption. However, it was another story with dry soil. You would think that something dry absorbs quickly, like an absorbent towel, but the opposite is true.

Water was barely absorbed a few milliliters and to get to this point it took much more time than with the other two glasses. Therefore, the soil would not be able to absorb large amounts of water during a storm after being dry. The water would stay above the ground and flooding would start.

Nahum Mendezauthor of ‘A geologist in trouble: a journey through time and into the depths of the earth’, told laSexta This may be due to two factors. The first factor it may be “the deposit of hydrophobic substances, which act as a film on the ground and hinder the absorption of water”. The second factor It may be due to “soil compaction, which closes the pores and makes it much more difficult for water to be absorbed.”

Both factors cause the dry soil due to drought reject the water One way or another. This is especially worrying for Spain due to the current drought and that these will only increase with climate change.

The Mediterranean has a warming of 1.1 ºC above the global average according to data from the latest report by the Intergovernmental Panel on Climate Change (IPCC), published in February 2022. Scientists’ predictions warn that there will be some rainfall reductions in the area of ​​between 5 and 20 percent.

Therefore, with the current drought that Spain is facing, a DANA that brings with it large amounts of rain or a sudden storm could very easily cause flooding because the ground does not have enough time to absorb the water before it accumulates and overflows.