Water Underground

How Water Moves Underground• Water underground trickles down between

particles of soil and through cracks and spaces in layers of rock

Effects of Different Materials

• Permeable materials have large and connected pores; materials such as sand and gravel allow water to pass through or permeate.

• Impermeable materials have few or no pores or cracks; therefore the water cannot pass through easily

• Examples: clay and granite

Water Zones

• **The area of permeable rock or soil that is totally filled or saturated, with water is called the saturated zone**

• **The top of the saturated zone is called the water table**

• The area above the water table is called the unsaturated zone

Bringing up Groundwater• In some areas, the water table meets the

surface• Aquifers:

– Any underground layer of rock or sediment that holds water is known as an aquifer**

– Size: small underground patch to the size of several states

Aquifers continued• Functions: drinking water, water for

crops, and water for livestock• Rate of Movement: depends on the slope

of the aquifer and permeability of rocks

Wells

• **People can obtain groundwater from an aquifer by drilling a well below the water table**

• If the level of the aquifer drops, a well can run dry

• The water table can rise after heavy rain or snow melts

Using Pumps• Mechanical pumps bring up groundwater• If water is pumped out too fast, a well will

run dry• New water that enters the aquifer from the

surface is called recharge

Relying on Pressure• **In an artesian well, water rises because

of pressure in an aquifer**• If groundwater becomes trapped between

two layers of impermeable rock or sediment, the pressure sends water spurting up through the punctured hole

• No pump is necessary