Teacher background information
What is an aquifer?
An aquifer is a large underground reservoir of water that is used to provide our drinking water. There are many types of aquifers some can be just a few feet underground and others can be as deep as 1,300 feet. Aquifers were created millions of years ago as rain ran down the hills and mountains carrying water and sediment. As the layers of sediment began to be deposited the water would soak through the layers of sediment until it hit a layer of impermeable rock.
The area where water fills the aquifer is called the saturated zone. The top of this zone is called the water table. The water table may be located as little as a foot below the ground’s surface or it can sit hundreds of feet down.
Where is groundwater found?
Groundwater can be found almost everywhere. The water table may be deep or shallow and may rise or fall depending on many factors. Heavy rains or melting snow may cause the water table to rise or heavy pumping of groundwater supplies may cause the water table to fall.
How is water from aquifers obtained?
Water in aquifers is brought to the surface naturally through a spring or can be discharged into lakes and streams. Groundwater can also be extracted through a well drilled into the aquifer. A well is a pipe in the ground that fills with groundwater. This water can be brought to the surface by a pump. Shallow wells may go dry if the water table falls below the bottom of the well. Some wells, called artesian wells, do not need a pump because of natural pressures that force the water up and out of the well.
How are groundwater supplies replenished?
Groundwater supplies are replenished or recharged by rain and snow melt. In some areas of the world people face serious water shortages because groundwater is used faster than it is naturally replenished. In other areas groundwater is polluted by human activities.
In areas where material above the aquifer is permeable, pollutants can readily sink into groundwater supplies. Groundwater can be polluted by:
- septic tanks
- leaky underground gas tanks
- overuse of fertilisers and pesticides.
If groundwater becomes polluted it will no longer be safe to drink.