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 deficit increase rapidly in recent weeks. So far, it has been the same as the record year of 1976, when the drought continued extra violently 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 in the summer will probably also be high.”

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 and soil 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, plants have a hard time 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 whole year has actually increased since 1960, the KNMI stated last October in the report Climate signal ’21† So it is wetter become. That is because of climate change. With every degree of warming, the air can hold 7 percent more water vapor, so there could potentially be more precipitation. However, this increase does not appear to be evenly distributed over 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 increased throughout the country, in all seasons. This is because the earth has warmed. In addition, the amount of solar radiation reaching the earth’s surface has increased in Europe. 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 has been investigating whether there are within There are differences in the Netherlands in precipitation and evaporation. The patterns appear to be different in the coastal area than in the interior. In the coastal area, up to 50 kilometers inland, precipitation in the summer half-year (April to September) has increased 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 either getting 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 suffer more from drought. The precipitation deficit has increased, especially in the spring, says Siegmund. “And those are the first months of the growing season.”

And the future? With further global warming, evaporation will continue to increase, 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 yet clear,” says Siegmund.

It can be okay

It seems that the months of April-September will be either drier or a lot drier in the Netherlands. It will partly depend, says Siegmund, on how quickly greenhouse gas emissions are reduced. If it goes fast, it can be easy. But it is also possible that further warming leads 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, will increase. It would fuel the drought in the Netherlands. In the report Climate signal ’21 KNMI does not call the increasing drought in spring and summer a risk for the Netherlands for nothing.

Hydrologists have been calling for extensive, structural interventions for several years now. The Netherlands will have to learn to better retain the water that falls abundantly in autumn and winter, in order to make up for shortages in 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 there quickly sinks into the sandy soil. Plants, including crops, get into trouble more quickly as a result.