Dry spring goes hand in hand with the record year 1976
And again the drought is harassing the Netherlands. Just like in 2018, 2019 and 2020. The KNMI saw the precipitation shortage start quickly in recent weeks. It is not yet the same as the record year 1976. Then the drought continued in June, July and August. It is still unclear whether that will also happen, says climate researcher Peter Siegmund of the KNMI. “But if the shortage is already so great in the spring, the maximum shortage will probably also arise in the summer.”
The KNMI determines the precipitation deficit daily, from 1 April to the end of September. It is the difference between the amount of water that disappears from plants through evaporation and the amount of precipitation that falls. If it rises, the soil dries out and the groundwater level drops. In the long run, it gets difficult and crops can be lost. Houses can sink. Dykes can weaken. The low water level can cause problems for inland skippers, as in 2018.
In the Netherlands, precipitation over the entire year has been confirmed since 1960, the KNMI determined last October in the report Climate signal ’21† So it is wetter become. That is because of climate change. With each degree, the air can hold 7 percent more water vapor, so there may be more falling. But that increase does not appear to be evenly distributed across the seasons. Especially in autumn and winter there is more. Precipitation decreased in the spring. “We don’t really know why that is,” says Peter Siegmund. Seen across the Netherlands, summers have become slightly wetter, but the rain falls more often in downpours.
Also read this article: The growing season is still young, but where is the rain?
Coastal area is different
Then the evaporation. It has been played all over the country, in all seasons. That comes used the earth has warmed. In addition, in Europe, the amount of solar radiation that reaches the Earth’s surface has been exported. There is as yet no conclusive explanation for the latter effect, says Siegmund. “In any case, the air has become cleaner as a result of environmental policy.” The cleaner air probably also limited cloud formation.
In recent years, the KNMI is investigating within There are differences in the Netherlands in precipitation and evaporation. The patterns in the coastal area differ from those in the interior. In the coastal area, up to 50 kilometers inland, precipitation in the summer half-year (April to September) has changed slightly since 1965. In the interior, the KNMI does not see a clear trend: no increase, no decrease.
It seems that the months of April-September are becoming drier, or a lot drier, in the Netherlands
But evaporation is stronger inland than on the coast, because it has warmed up a bit more. Added together, this causes the interior to experience more drought. In the spring there is a shortage of precipitation. “And those are the first months of the growing season.”
And the future? With further development, Siegmund says. The picture is less clear for precipitation in spring and summer. It will increase slightly in Northern Europe, according to the latest climate models. It will decline sharply in the Mediterranean. The Netherlands is in between. “Which way we roll is not clear,” says Siegmund.
It can be okay
It seems that the months of April-September are becoming drier, or a lot drier in the Netherlands. It will help, says Siegmund, how quickly emissions are reduced. If it goes fast, it can be easy. But it is also possible that further guidelines lead to a change in the air circulations. In the models, KNMI sees a decrease in westerly winds that supply moist air from the North Sea in the summer. The easterly winds, which bring dry, warm air from the Mediterranean, are increasing. It would fuel the drought in the Netherlands. In the report Climate signal ’21 the KNMI that the decrease in the spring and summer poses a risk to the Netherlands for a reason.
Hydrologists have been calling for extensive, structural interventions for several years now. The Netherlands will have to learn the water in the autumn and winter to make up for shortages in the spring and summer. This certainly applies to the interior. And, zooming in further, especially for the higher sandy soils (the eastern part of the Netherlands). Because the rain that falls, quickly sinks into the sandy soil. Plants, including crops, get into trouble more quickly.
A version of this article also in the newspaper of May 16, 2022