Groundwater: aquifers, springs and wells
Not all the water is on the surface. About 30% of the fresh water on our planet is underground. This water is called groundwater.
How does an aquifer form?
- 1🌧️ Precipitation falls
Rain and melted snow fall on the ground.
- 2⬇️ It filters down
The water goes down through porous rock: rock with tiny holes that liquids can pass through.
- 3🪨 It stops
Under the porous rock there is impermeable rock. Water cannot pass through it, so it stops there.
- 4💧 An aquifer
The groundwater collects in the layers of porous rock. This is an aquifer.
How does groundwater come to the surface?
The groundwater flows naturally out of the ground. Many rivers begin at a spring.
People dig a deep hole down to the aquifer to bring the water up to the surface.
A sponge is porous: it is full of tiny holes and water goes into it. A plastic plate is impermeable: water cannot pass through it. Rocks can be like the sponge or like the plate!