Europe has a water problem: groundwater decreases and already suffers from a severe drought since 2018

This is confirmed by the satellite data analyzed by TU Graz for the EU G3P project

[27 Gennaio 2023]

According to the Technische Universität Graz (TU Graz), “Europe has been experiencing a severe drought for years. Across the continent, groundwater levels have remained consistently low since 2018, although extreme weather events with flooding temporarily paint a different picture.

The beginning of this situation had already been documented in study “Quantifying the Central European Drugs in 2018 and 2019 With GRACE Follow-On”, published in July 2020 on Geophysical Research Letters by a team of German researchers from the GeoForschungsZentrum (GFZ) led by Eva Boergens, who had observed that «During the summer months of 2018 and 2019 there was a significant water shortage in Central Europe. Since then, there has not been a significant rise in groundwater levels. Since then, as data analyzes by Torsten Mayer-Gürr and Andreas Kvas of TU Graz’s Institut für Geodäsie, carried out as part of the European Union’s Global Gravity-based Groundwater Product (G3P​​) project, show, « Levels have remained consistently low.

To observe the world’s groundwater resources, documenting their changes in recent years, the Austrian researchers used satellite gravimetry and say that «The effects of this prolonged drought were evident in Europe in the summer of 2022. stagnant that slowly disappeared and with numerous impacts on nature and people. Not only have many aquatic species lost their habitat and barren soils have caused many problems for agriculture, but Europe’s energy shortage has also worsened as a result. Nuclear power plants in France did not have cooling water to produce enough electricity, and hydroelectric power plants could not function without sufficient water either.

At the heart of the G3P project are the twin satellites Tom and Jerry, which orbit the Earth in a polar orbit at an altitude of just under 490 kilometers. At the TU Graz they highlight that «The distance between the satellites of about 200 kilometers is important. The one behind does not have to reach the one in front, which is why they were given the name Tom and Jerry in reference to the cartoon characters. The distance between satellites is measured constantly and accurately. If they fly over a mountain, the satellite in front is initially faster than the one behind due to the greater mass below it. Once over the mountain, it slows down a little more, but the rear satellite accelerates as it reaches the mountain. Once both have cleared the mountain, their relative speed is once again established. These distance variations over large masses are the main measured quantities for determining the earth’s gravitational field and are determined with micrometre precision. By way of comparison, a human hair is about 50 micrometres thick. All this takes place at a flight speed of around 30,000 km/h. The two satellites thus manage 15 Earth orbits per day, which means that after a month they achieve complete coverage of the earth’s surface. This in turn means that TU Graz can provide a gravity map of the Earth every month.”

Mayer-Gürr adds: “The processing and computational effort is quite large. We have a distance measurement every 5 seconds and thus about half a million measurements per month. From this we then determine the maps of the gravitational field».

But the gravity map does not yet determine the amount of groundwater. This is because the satellites show all mass changes and do not distinguish between sea, lakes or groundwater. To do this it was necessary to cooperate with all the other European partners of the G3P project. Mayer-Gürr and his team provide the total mass, from which mass changes in rivers and lakes, soil moisture, snow and ice are then subtracted and finally only groundwater remains.

The result of this cooperation shows that The water situation in Europe has become very precarious» and Mayer-Gürr did not expect this on such a large scale: «A few years ago I never imagined that water would be a problem here in Europe, especially in Germany or Austria. We are actually having problems with the water supply – we need to think about it. First you need to be able to document the continuing drought using data and have ongoing satellite missions on this in space.

The European Space Agency ESA and its US counterpart NASA will continue this research with the MAGIC (Mass-change And Geoscience International Constellation) project. TU Graz will be on board again for data evaluation.