2. Engage/Explore  Spring water  What was the original source of this water?  Where does the water in springs and wells come from?

3. Underground Layers  Where does underground water come from?  Answer: Precipitation that soaks in the ground and trickles downward.  Water underground trickles down between particles of soil and through cracks and spaces in layers of rock.

4.  Pores – space between rocks and soil  Permeable - materials that allow water to easily pass through  Examples of permeable materials are sand and gravel.

5.  Impermeable - materials that water cannot pass through easily.  Examples of impermeable materials are clay and granite.  Saturated zone - the area of permeable rock or soil that is totally filled or saturated with water.

6.  Water table - the top of the saturated zone.  Unsaturated zone - the layer of rocks and soil above the water table. (No water)

7. Layers Underground  What is different about the pores in the two pictures?  Which picture represents a permeable rock layer?  In this picture how do the pores differ above and below the water table?

8. Aquifers  Aquifer - any underground layer of rock or sediment that holds water.  Size - small underground patch of to an area the size of several states.

9. Aquifers  The huge Ogallala aquifer lies beneath the plains of the west, from S. Dakota to Texas. It provides drinking water and water for crops and livestock.

10. Aquifers  The water in aquifer moves only a few centimeters a day which equals out to be about 10 meters a year.  The movement depends largely on how steeply the aquifer slopes and how permeable the rocks are.

11. Wells  People can obtain groundwater from an aquifer by drilling a well below the water table.  Compare the well and dry well.

12. Wells  History of wells  Dug by hand  Lined with brick or stone to keep the walls from collapsing.  Lower and raise a bucket to bring up water.  Today, most are dug with well- drilling equipment.

13. Wells  Pumping water out of an aquifer lowers the water level near the well. If too much water is pumped out too fast, the well may run dry.  Then it may be necessary to dig deeper to reach the lowered water table or to wait for rainfall to refill the aquifer.

14. Wells  Recharge - New water that enters the aquifer from the surface.  Artesian well - a well in which water rises because of pressure within the aquifer.

15. Bringing Groundwater to the Surface  Springs - where the water table meets the ground surface, groundwater bubbles or flows out of cracks in the rock in places.

16. Draw a picture to show underground water and label the Saturated zone, unsaturated zone, water table, aquifer, permeable layer and impermeable layer.