Satellite data shows continued severe drought in Europe

Satellite data shows continued severe drought in Europe

Already in 2019 the amount of groundwater in Central Europe was very low. Credit: Andreas Kvass, Too Graz

Europe has been suffering from severe drought for years. Across the continent, groundwater levels have been consistently low since 2018, even if extreme weather events with floods temporarily give a different picture. The onset of this tense situation is documented in Study 2020 by Eva Boergens in Geophysical Research Letters. In it, she indicated that there was a significant water shortage in Central Europe during the summer months of 2018 and 2019.

Since then, there has been no significant rise in Groundwater levels. Levels remained consistently low. This is evidenced by data analyzes by Torsten Mayer-Gürr and Andreas Kvas of the Institute of Geodesy at the Graz University of Technology (TU Graz). As part of the European Union’s Global Gravity-Based Groundwater Products Project (G3P), they used satellite gravimetry to monitor the world’s groundwater resources and document changes in recent years.

Far-reaching consequences

The effects of this prolonged drought were evident in Europe in the summer of 2022. Dry riverbeds and stagnant waters that are slowly disappearing, with many implications for nature and people.

Not only did many aquatic species lose their habitats and the dry soil caused many problems for agriculture, but also the energy shortages in Europe got worse as a result. Nuclear power plants in France lack cooling water To generate enough electricity, hydroelectric plants cannot do their job without enough water.

Groundwater measurement from space

How can geodesists at TU Graz use data from space to make accurate data about aquifers? At the heart of the G3P project are twin satellites called Tom and Jerry, which orbit the Earth in a polar orbit at an altitude of just under 490 kilometers. The distance between the satellites of about 200 km is significant. The person in the back should not keep up with the person in front of him, which is why they are called Tom and Jerry in reference to the cartoon characters.

Satellite data shows continued severe drought in Europe

GRACE’s Tom and Jerry satellites measure mass changes on Earth. Credit: NASA-JPL-Caltech

The distance between satellites is measured continuously and accurately. If you fly over a mountain, the satellite in front of it is initially faster than the one behind it because of the increasing mass below it. Once it crosses the mountain, it slows down slightly again, but the back satellite accelerates once it reaches the mountain. Once both are over the mountain, their relative speed is determined again. These changes in distance over large masses are the main measurement variables for determining the Earth’s gravitational field and are verified with micrometer precision.

Earth’s monthly gravity map

All this happens at a flight speed of about 30 thousand km / h. Thus, the two satellites run 15 Earth orbits per day, which means that they achieve complete coverage of the Earth’s surface after one month. This in turn means that TU Graz can provide a gravity map of the Earth every month.

“The processing and computational efforts here are very large. We have a distance measurement every five seconds, so about half a million measurements per month. And then we map the gravitational field,” says Torsten Mayer-Gürr.

Mass minus mass equals mass

However, the gravity map has not yet determined the amount of groundwater. This is because satellites show all mass changes and do not distinguish between sea, lakes or groundwater. This requires cooperation with all other partners of the EU G3P project. Torsten Mayer-Gürr and his team provide the total mass, from which mass changes in rivers and lakes are then subtracted, soil moisture, snow and ice are also subtracted, and finally only groundwater remains.

Each of these other audiences has its experts contributing their data here. These are located in Austria (University of Technology Graz, University of Technology Vienna, Earth Observational Data Center EODC), Germany (GeoForschungsZentrum GFZ in Potsdam), Switzerland (University of Bern, University of Zurich), France (CLS Satellite Assembly, Laboratories d’Etudes en Géophysique et Océanographie Spatiales LEGOS, Magellium), Spain (FutureWater), Finland (Finnish Meteorological Institute) and the Netherlands (International Groundwater Resources Assessment Center IGRAC).

Europe has a water problem

The result of this cooperation shows that the water situation in Europe is now very precarious. Torsten Mayer-Gürr did not expect this on a large scale. “A few years ago, I would never have imagined that water would be a problem here in Europe, especially in Germany or Austria. We are actually having problems with the water supply here – we have to think about this,” he explains. From his point of view, it is necessary first and foremost to be able to document ongoing droughts using data and to be continuous Satellites missions on this in space.

more information:
For more information about satellite geodesy, see the article “A cat chasing a mouse in space. ”

Information about the G3P project:

the quote: Satellite data showing persistent severe drought in Europe (2023, January 25) Retrieved January 25, 2023 from

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