Abstract
Groundwater resources in Euro-Mediterranean countries provide a large part of the population’s water supply and are affected to varying degrees by anthropogenic use and climatic impacts. In many places, significant groundwater-level declines have already been observed, indicating an imbalance between natural groundwater recharge and groundwater abstraction. The extent of changes in groundwater storage (GWS) in the period 2003–2020 is quantified for the Euro-Mediterranean region using the latest data from the Gravity Recovery and Climate Experiment (GRACE/GRACE-FO) satellite mission and recently reanalyzed ERA5-Land climate data from the European Centre for Medium-Range Weather Forecasts. The results are set in relation to the prevailing climate, the regional hydrogeological setting, and annual groundwater recharge and abstractions on country level. Analysis of the mean annual trends over the study period shows significant decreases in GWS in many countries of Europe, Northern Africa and the entire Arabian Peninsula. Overall, there are significantly negative trends in about 70% of the study region. The mean of the trends across the Euro-Mediterranean region is –2.1 mm/year. The strongest negative trends in GWS per country are observed in Iraq and Syria (–8.8 and –6.0 mm/year, respectively), but also countries in central and eastern Europe are affected by depleting aquifers. The results are a clear indicator of the already medium-term groundwater stress in the Euro-Mediterranean region, which is expected to increase in the future, and demonstrate the need for adapted strategies for sustainable groundwater management on a transregional scale in the context of climate change and population growth.
Highlights
The natural occurrence of groundwater is largely controlled by processes and factors of the prevailing climate, thegeological environment and the geomorphological characteristics (Mukherjee et al 2021), and varies in its spatiotemporal availability
It should be noted that Gravity Recovery and Climate Experiment (GRACE)-derived data always refer to the entire vertical groundwater column and represent the sum of groundwater storage (GWS) changes in multilayered aquifer systems, where present, and observed groundwater level records of individual aquifers may differ
The strongest negative average trends can be observed for Iraq (–8.8 mm/year) and Syria (–6.0 mm/year), and other countries of the Arabian Peninsula show clear negative trends, as for example Kuwait (–5.7 mm/year), Jordan (–4.3 mm/year) and Saudi-Arabia (–3.9 mm/year)
Summary
The natural occurrence of groundwater is largely controlled by processes and factors of the prevailing climate, the (hydro)geological environment and the geomorphological characteristics (Mukherjee et al 2021), and varies in its spatiotemporal availability. The situation is further exacerbated by population growth and the associated increase in demand for fresh water for agricultural, industrial and domestic uses (Le Page et al 2021) In such areas, the opposing trends of decreasing groundwater recharge and increasing abstraction will further lead to dropping groundwater levels. The opposing trends of decreasing groundwater recharge and increasing abstraction will further lead to dropping groundwater levels This effect is even more noticeable in deep aquifers that experience very little or no recharge and are considered as nonrenewable, fossil groundwater resources, as for example in a few aquifers in Jordan (Charalambous 2016), Saudi Arabia or Libya (Gonçalvès et al 2020; Khater et al 2003). This means that sufficient availability of groundwater for future generations is at risk
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