„A widespread belief is that groundwater levels are continuously declining everywhere in southwestern Europe. However, a closer examination of the data reveals that the situation is more complex“, says UFZ hydrologist Dr. Seifeddine Jomaa.

Climate change and anthropogenic pressures can threaten groundwater availability, especially in southwestern Europe. To evaluate this thread, an international research team coordinated by the Helmholtz Centre for Environmental Research (UFZ) used data from several decades from more than 12,000 groundwater wells in Portugal, Spain, France, and Italy. The result: During the time period from 1960 to 2020, 12 % of the groundwater reserves showed a decline, 68 % remained stable and 20 % of the wells revealed even rising levels.

Regions with stable or increasing recharge rates

Stable groundwater levels are primarily located in temperate regions with year-round high precipitation, such as northern France.

In other areas, like the lower Po River basin near Ravenna, groundwater levels are even rising due to natural and anthropogenic factors  and land subsidence, requiring surface water drainage and groundwater pumping to prevent flooding.

Regions that are mostly threatened by declining levels

Groundwater levels are primarily declining in semi-arid regions with intensive agriculture and frequent droughts. There are many places, such as Tarbes in France and Medina del Campo in Spain, where groundwater levels have been declining for decades.

„These four Mediterranean countries are responsible for a large part of the EU’s fruit, vegetable, and grain production, with groundwater supplying 30-50% of irrigation,“ says Seifeddine Jomaa.

Furthermore, the team found wells with declining groundwater levels even in temperate regions, that is to say near larger cities and industry. Since the 1960s, for example, groundwater levels in the metropolitan areas of cities such as Lyon, Nice, Modena, and Bordeaux have been declining. In Bordeaux, the ninth-largest city in France, the high groundwater consumption is attributed to increasing domestic use. The popular French tourist destination, Béziers, has seen a significant decline in groundwater levels due to increased extraction to supply drinking water for summer tourists.

Effective management can make groundwater levels rise again

While groundwater decline in urban and industrial areas is not easily halted, the researchers found effective management approaches in semi-arid, agricultural regions, which lead to the recovery of groundwater levels, as seen in La Mancha Oriental in Spain. Until the 1990s, groundwater levels were declining due to excessive irrigation.

„As a result, sections of the Júcar River dried up in 1994 for the first time ever. This dramatic event prompted farmers to create a water user association that aimed to stop the decline in groundwater levels through a combination of monitoring, remote sensing, and individual water use plans. These measures effectively reversed groundwater level trends in the region,“ says coauthor J. Jaime Gómez-Hernández, hydrogeologist at the Technical University of Valencia.

Lessons to learn for Germany

The researchers are convinced that southwestern Europe can provide lessons for groundwater management in Germany. In detail, the northern country could benefit from the experiences, how groundwater can be optimally used and which irrigation measures are more effective. In addition, southwestern Europe provides insights how to enhance stakeholder engagement and what mistakes should be avoided.

This study was supported by InTheMED and OurMED projects, which are part of the PRIMA (Partnership for Research and Innovation in the Mediterranean Area) Program funded by the European Union’s Horizon 2020 research and innovation program.