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When we talk about freshwater, most people picture rivers or lakes. Maybe glaciers. But a surprising amount of the world’s freshwater is actually stored out of sight, underground. Aquifers — natural formations made of sand, gravel, or cracked rock — act like vast, slow-moving sponges, holding water that seeps down from rain and snow. It’s this groundwater that often keeps farms running, taps flowing, and ecosystems alive, especially in drier regions.
In Europe, efforts to map and monitor these resources have become more detailed over the years. The European Commission’s Joint Research Centre has produced maps showing where aquifers lie, their depth, and how they interact with local geology and climate. It’s the kind of data that can inform everything from agriculture to climate adaptation.
Think of an aquifer as an underground reservoir — not a pool of water exactly, but more like a network of rock and soil that can absorb and carry it. Water trickles in from above when it rains or snows (that’s the recharge), and it leaves either through wells, natural springs, or plant roots (that’s the discharge). If you draw more water out than what’s going back in, the balance tips — and eventually the supply shrinks.
The world map below shows how deep the Earth’s modern groundwater would be if it were pooled above ground.
Some Countries Have More Water Than Others
According to the World Bank, countries like Brazil and Canada are rich in renewable freshwater. Brazil, for instance, holds over 5,600 cubic kilometers of it, much of it underground. Other countries near the top of the list include Russia, the U.S., and China. But this isn’t the full story. High population, pollution, and poor management can turn even water-rich regions into places with serious shortages.
Here are the top ten countries in terms of total renewable freshwater, based on data from the World Bank:
Rank
Country
Cubic kilometers
% of Total
1
Brazil
5,661
13.2
2
Russia
4,312
10.1
3
Canada
2,850
6.7
4
United states
2,818
6.6
5
China
2,813
6.6
6
Colombia
2,145
5
7
Indonesia
2,019
4.7
8
Peru
1,641
3.8
9
India
1,446
3.4
10
Myanmar
1,003
2.3
11
DR Congo
900
2.1
12
Chile
885
2.1
13
Venezuela
805
1.9
14
Papua New Guinea
801
1.9
15
Malaysia
580
1.4
16
Australia
492
1.1
17
Philippines
479
1.1
18
Ecuador
442
1
19
Japan
430
1
20
Mexico
409
1
–
Other
9,875
23.1
The numbers are large, but they mask important regional and seasonal variations — and not all that water is easy to reach.
Recharge Rates Vary Widely
In some parts of the world, rainwater moves quickly into the ground. Hawaii, for example, has porous volcanic rock and plenty of rainfall. Florida, with its limestone base, also sees high recharge rates, especially during the wet season.
Elsewhere, things are slower. The Disi Aquifer, which straddles Jordan and Saudi Arabia, is considered a fossil aquifer — meaning it contains water that’s thousands of years old and barely recharges today. Only around 50 million cubic meters of water enter it annually, while extraction far exceeds that. Once it’s gone, it’s gone.
China’s North China Plain faces a different challenge. There, groundwater is heavily used for farming, but rainfall and recharge aren’t enough to keep up. Water levels are dropping, and in some places, the land is starting to sink.
Some areas are experimenting with managed recharge systems — channeling stormwater or river overflow into aquifers. These systems can help, but they’re not always enough to counterbalance heavy pumping.
Groundwater Faces New Pressures
Climate change is shifting precipitation patterns. Droughts are becoming more common, and in coastal areas, sea-level rise is pushing saltwater into freshwater aquifers — a process called saltwater intrusion.
At the same time, population growth and agriculture are increasing demand. Some aquifers are being drained faster than nature can refill them. Others are threatened by pollution — nitrates from fertilizers, industrial waste, even microplastics.
Once groundwater is contaminated, cleaning it up is incredibly difficult. And because water moves so slowly underground, the damage can persist for decades.
