Please fill out and return this sheet after viewing Program #21.   If you are unsure of an answer, give your best intelligent guess.

1.  What is the largest source of fresh water on Earth?

Groundwater (if you consider that ice isn't technically available until it has melted)

2.  What is porosity?  What is permeability?

The space in rocks that is available to fluids or gas

3.  What type of material makes a good aquifer?

gravels or sands (conglomerate or sandstone)

4.  What type of material makes a good aquiclude?

clays (shales)

5.  Why does groundwater tend to dissolve limestone?

Groundwater has atmospheric CO₂ dissolved in it, which makes it slightly acidic.

6.  What are stalactites?  stalagmites?

Limestone deposits that hang from the ceiling of a limestone cave (stalactites), and limestone deposits that build up from the floor of the cave.

7.  What is one way of tracing the pathway of groundwater flow?

Using dyes in the groundwater

8.  What is the saturated zone?  unsaturated zone?

The saturated zone is the region of the ground in which the pores are filled completely with water.  The unsaturated (aerated or "vadose") zone is the part of the groundwater generally above the saturated zone in which the pores are filled with air.

9.  What is the boundary between these two zones?

The water table.

10.  What are some features that form when the water table intersects the ground surface?

Springs, rivers, and lakes

11.  What is an artesian aquifer?  How does it form?

An artesian aquifer is one in which the water can be tapped, and the water will rise to the surface under its own pressure.  It forms by an aquifer becoming sandwiched between two confining layers (aquicludes or aquitards), and the aquifer bends up and becomes exposed at the ground surface where it becomes available as a recharge zone.  This builds up pressure on the groundwater so that it is able to rise to the surface.

12.  How can groundwater be managed appropriately so that it is always available for use?

Groundwater must not be extracted at a faster rate than it is replenished.  If recharge zones may be set up, then this can allow water (from lakes or ponds) to drain into the groundwater to replenish what is lost.  Other concerns include avoiding groundwater contamination by pollutants or encroachment by seawater.

13.  What can be done to make landfills less harmful to groundwater?

Landfills are lined with a low permeable layer, such as clay, which prevents seepage into the water table.  The landfill may also be set up to collect drainage water from the base before it has a chance to seep away.

14.  What is likely to happen if groundwater is drawn down rapidly in coastal areas?

Salty groundwater (brines) from the oceans will slowly move in to replace what freshwater has been lost.