Groundwater and aquifers — Earth science, 14–17 years
Water below ground is not usually an underground lake. It moves slowly through pores and cracks, and aquifers store and supply water to people and ecosystems.
What groundwater is
Rain and melting snow can seep into the ground instead of running away at the surface. Below the water table, pores and cracks in soil or rock are filled with water; this is groundwater. An aquifer is a layer that stores and transmits enough groundwater for wells or springs to use.
Why aquifers matter
People needed water during dry seasons and in places without reliable rivers. Aquifers can provide that hidden reserve, but they refill only as fast as water infiltrates. Pumping faster than recharge lowers the water table, dries springs and may cause land to sink or seawater to enter coastal wells.
Worked example: recharge balance
Suppose a small aquifer receives 1,000 cubic metres of recharge each month. Wells remove 800 cubic metres, so storage rises by 200 cubic metres. During a dry month, recharge falls to 300 while pumping stays at 800; storage then drops by 500. Repeating that deficit lowers the water table, even though water is still present.
Trap: groundwater is not endless
It is reasonable to think that underground water is safe from running out because rain seems to disappear into a huge hidden space. In reality, many aquifers refill slowly, and some contain water trapped for thousands of years. A well can keep producing for a while after overuse begins, hiding the problem until levels fall sharply.
Groundwater in decisions
Groundwater supplies drinking water, irrigation and many springs. Farmers and towns can reduce pressure by using efficient irrigation, protecting recharge areas and limiting polluted runoff. A leaking fuel tank or fertiliser can travel through soil into an aquifer, where contamination is difficult and expensive to remove.
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