Even if it doesn't seem so at the moment, the groundwater level in Europe is still lower than it should be. This is proven by current measurements using satellites. According to this, soil and groundwater hardly recovered from the extreme drought years of 2018 and 2019 in 2022 either. According to the researchers, the dry phase in Europe is continuing - even intermittent extreme heavy rainfall does little to change this.
Climate change is also leading to more frequent and severe weather extremes in Europe. This is evidenced by heavy rainfall such as in July 2021 in western Germany, but also persistent heat and dry phases. This is especially true for the period from 2018 to 2020: the summers were too dry and hot for three years in a row. The lack of rain caused rivers to dry up, crops to wither and entire forest areas to turn brown. In addition, there were new heat records in Germany and elsewhere in Europe. Comparative analyzes have shown that this drought was historically unique for Central Europe.
Groundwater measurement using twin satellites
But was this just a temporary anomaly? And how has it been since then? In fact, the year 2021 was significantly rainier than its predecessors and the summer was also less hot. Forests, soil and groundwater were able to replenish part of their water deficits. But in 2022 the drought returned: the summer of 2022 was one of the warmest ever recorded in Europe, and large parts of the continent again failed to rain sufficiently. Rivers and lakes dried up, farmers' crops dried up. Because the river levels were so low, nuclear power plants in France and many hydroelectric power plants lacked the water they needed - exacerbating the energy crisis.
Torsten Mayer-Gürr and Andreas Kvas from the Institute of Geodesy at Graz University of Technology have investigated what this means for groundwater in Europe. You are part of a European team that uses satellite gravimetry to continuously monitor the world's groundwater resources. As part of the EU project "Global Gravity-based Groundwater Product" (G3P), they are evaluating data from the GRACE-FO mission, which consists of two satellites orbiting the globe together. Both satellites follow each other at a distance of about 200 kilometers and monitor their relative position down to the micrometer.
Hardly any recovery of groundwater since 2018
These measurements are related to drought and groundwater because the mass of groundwater in the subsoil or other larger water masses influences the earth's gravitational field. This changes the force with which Earth's gravity pulls on the satellite just a tiny bit - and changes their relative position. “We have a distance measurement every five seconds, which is about half a million measurements per month. We then use this to determine gravity field maps,” explains Mayer-Gürr. A complete gravity field map of the earth is created every month. By comparing all the factors that influence the earth's gravitational field, the researchers of the G3P project can determine the groundwater levels.
The current data for Europe shows that our continent still has a significant groundwater deficit. There has therefore been no significant rise in groundwater levels since 2018, and the levels are constantly low. According to the researchers, the water situation in Europe has now become precarious. "A few years ago I would not have thought that water could be a problem here in Europe, especially in Germany or Austria," says Mayer-Gürr. "We're actually getting problems with the water supply here, so we have to worry." It is all the more important to continue to closely monitor the groundwater situation.
Source: Graz University of Technology