FIGURE2 The world’s major groundwater basins
ARCTIC OCEAN
Russian platform basins
Arctic Circle
Ogalalla aquifer
ATLANTIC
PACIFIC
Tropic of Cancer
Lake Chad basin
OCEAN
Arabian aquifer system
OCEAN
Equator
Amazon basin
INDIAN
Tropic of Capricorn
OCEAN
Great Artesian basin
Key
Groundwater basin
4000 km
0
2000
Source: BGR & UNESCO 2008: Groundwater Resources of the World 1 : 25000000. Hannover, Paris.
SkillBuilder discussion Concluding and decision-making, Communicating 1. Which regions of the world are most reliant on groundwater from these major basins?
2. How does the distribution of major groundwater basins correlate with global population centres and agricultural regions? 3. What are some environmental concerns associated with the depletion or contamination of groundwater in these major basins?
9.3.2 Artesian water An artesian aquifer is trapped between rocks that water can’t pass through. When a well is drilled, water may gush out. It stops if the pressure drops, or the well is sealed. Groundwater and surface water are linked. Groundwater refills when surface water soaks into aquifers. This is called groundwater recharge (shown in FIGURE3 ). Groundwater is essential for drinking, farming and industry. Some companies bottle spring and mineral water or use it to make drinks like soft drinks and beer. Bore water is used for watering parks, golf courses andcrops. Groundwater moves very slowly and can take years to reach deep aquifers. This makes it a non-renewable resource, called ‘fossil water’ because it can’t be replaced quickly.
Did you know? People once thought groundwater would never run out, but in some places, it’s running low. Pumping too much can make land sink. Cities like Jakarta and Mexico City are sinking because of this. If we use more groundwater than is replaced, aquifers can dry up.
TOPIC9 Water in the world 253
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