1. Earth Science
-presents-
Groundwater

2. What You’ll Learn How large amounts of water are stored underground.
How groundwater dissolves limestone and forms caves and other natural features.
How groundwater is removed from the ground by humans and what problems endanger our groundwater supply.

3. Vocabulary Terms Infiltration Porosity Zone of saturation Water table
Permeability
Impermeable
Aquifer
Topography
Cave
Stalactite
Stalagmite
Travertine
Spring
Geyser
Drawdown
Artesian Well

4. Movement and storage of groundwater3%
freshwater
The Hydrosphere
97%
Ocean Water
The hydrosphere is
water on or in
Earth’s crust.
“hydros” is the Greek word for water.

5. Movement and storage of groundwater
10%
50%
90%
From the 3% of
freshwater, how much do you think is trapped in the polar ice caps and glaciers?
97%
Ocean Water

6. What is the greatest source? ? ? ?
Polar caps
Glaciers
Both a and b
What is the greatest source
of freshwater on Earth?

7. Movement and storage of groundwater
Precipitation and Groundwater

8. Movement and storage of groundwater
Precipitation and Groundwater
Much of the precipitation
that falls on land enters the ground through a process called infiltration and becomes groundwater.
Only a small portion of runoff is directly returned to the oceans through streams and rivers.
Precipitation

9. Movement and storage of groundwater
Precipitation and Groundwater
Solid precipitation such as snow takes a long while before it becomes runoff or infiltrates to become groundwater.
Eventually, the groundwater returns to the surface through springs and then flows back to the ocean.
Precipitation

10. Movement and storage of groundwater
The amount of space between rock particles in underlying sediment is referred to as
porosity.
Well sorted High
sediments Porosity

11. Movement and storage of groundwater
The amount of space between rock particles in underlying sediment is referred to as
porosity.
Poorly sorted Low
sediments Porosity

12. Movement and storage of groundwaterb.
Q: Which of these two do you think will absorb groundwater faster after rainfall?

13. Movement and storage of groundwater
The porosity of sand can range from 2% to 50% ! The greater the porosity…the faster water is absorbed.

14. Movement and storage of groundwater
The Zone of
Saturation
The depth below the Earth’s surface at which groundwater completely fills the pores of material is called the zone of saturation.

15. Movement and storage of groundwater
The Zone of
Saturation
The upper boundary of the zone of saturation is called the water table.

16. Movement and storage of groundwater
The Zone of
Saturation
Only the water that exists in the
Zone of saturation is called groundwater.

17. Movement and storage of groundwater
The Zone of
Saturation
Zone of aeration – materials are moist
but contain mostly air.

18. Movement and storage of groundwater
The Water
Table
The depth of the water table varies with the slope of the land.

19. Movement and storage of groundwater
The Water
Table
The topography of the water table follows the contours of the land.

20. Movement and storage of groundwater
The Water
Table
The water table rises and falls depending on the season and the amount of precipitation.

21. Where is the water table closest to Earth’s surface?
Floodplain
A Swamp
A Hilltop
Where is the water table closest to Earth’s surface?

22. Movement and storage of groundwater
In saturated sediment all materials are coated with a thin film of motionless water.
In coarse grained materials like sand, this film occupies a relatively
small portion of the “pore space”.
1 mm

23. Movement and storage of groundwater
Because of this
moving water can flow freely past the open pore spaces.
Groundwater flows downhill due to gravity and in the direction of the landscape slope.
1 mm

24. Movement and storage of groundwater
Because water has to squeeze through the small pores in the subsurface material, it usually travels very slow.
1 mm

25. Movement and storage of groundwater
1 mm
vs.
0.1 mm
Sometimes the pores are so small not even a single water molecule can get through.

26. Movement and storage of groundwater
1 mm
vs.
0.1 mm
The ability of a material to let water pass through it is called permeability.

27. Movement and storage of groundwater
1 mm
vs.
0.1 mm
Flow rates for these materials can be as fast as 1 m/h (one meter per hour).
Q: Which of the two examples of sediment above have the highest permeability.
Highly permeable materials include sandstone, limestone, and fractured bedrock.

28. Movement and storage of groundwater
0.1 mm
0.1 mm
With such tiny pores, some fine grained material is considered impermeable.
Examples of impermeable materials are silt, clay, and shale.
Flow velocities in impermeable materials are often measured in m/yr (meters per year).

29. What two factors determine the flow velocity of groundwater?
Answer:
The flow velocity depends on the slope of the water table and the permeability of subsurface materials.
What two factors determine the flow velocity of groundwater?

30. Movement and storage of groundwater
Most groundwater flow takes place through permeable layers called aquifers.

31. Movement and storage of groundwater
Impermeable layers called aquacludes are barriers to groundwater flow.

32. ? ? ? ? What is an aquifer? Answer:
An aquifer is a permeable layer that allows groundwater to flow through it.

33. Springs Groundwater Systems
Aquifers are commonly composed of sand, gravel, sandstone and limestone.
Remember: Limestone is easily dissolved by groundwater…..that’s how cavities in aquifers appear. (A cavity is an open space…like a cave).

34. Groundwater Erosion and Deposition
Caves
Caves form near or below the water table.

35. Groundwater Erosion and Deposition
Caves
Stream valleys are lowered and streams become empty as they infiltrate cave openings.

36. Groundwater Erosion and Deposition
Caves
Collapsing caves (or dissolved bedrock) near the surface of the Earth produce sink holes on the Earth’s surface.

37. ? ? ? ?
Answer:
Since there are a lot of open spaces due to dissolved limestone, the ground water can flow FASTER in this area of an aquifer.
Since the Limestone area of an aquifer is filled with “cavities”, how would this affect the rate of groundwater flow?

38. Groundwater Erosion and Deposition
Caves
Caves are usually located just beneath the water table.
As water drips from the ceiling of a cave, it leaves behind small trace amounts of minerals found within the water itself.
After a long period of time, these minerals collect to form cone shaped structures called “stalactites”.

39. Groundwater Erosion and Deposition
Caves
As the water drips to the floor, minerals left begin to build up mound shaped, dripstone deposits.
This type of deposit is called a “stalagmite”.
Eventually, stalactites and stalagmites will join together to form dripstone columns within the cave!

40. So what happens when an aquifer meets an aquaclude?
Answer:
The aquaclude stops water flow…so when aquifers and aqucludes meet, water is forced out of the Earth….see photo on page 249.
So what happens when an aquifer meets an aquaclude?

41. Springs Groundwater Systems
When aquifers meet aquacludes at or near the surface of the Earth, water is forced out of the Earth….thus producing a SPRING.

42. Groundwater
Systems
Springs
The volume of water produced by a spring can be a mere trickle or a raging river!
In a “Karst Region”, springs yield extremely fast moving waters….. they’re called Super Springs.

43. Springs Groundwater Systems
In areas where there is horizontal sedimentary rock, Springs emerge in valleys very close to aquifers.

44. Springs can occur at the edges of perched water tables.
Groundwater
Systems
Springs
Springs can occur at the edges of perched water tables.

45. Springs Groundwater Systems
Springs can also emerge at fault lines.
Sometimes Springs emerge along fault lines!

46. Sometimes Springs emerge along fault lines!
Groundwater
Systems
Springs
In Limestone regions, springs discharge water from underground pathways.
Sometimes Springs emerge along fault lines!

47. Temperature Of Springs Groundwater vs. Air Groundwater Systems
Spring water can be hot, warm, or cold….depending upon where the spring is located.
Winter Summer
Temperature
Groundwater vs. Air
Air
Water
Air
Water

48. Temperature
Of Springs
Groundwater
Systems

49. Temperature Of Springs Groundwater Systems
Hot Springs are defined as groundwater with temperatures higher than that of the human body.

50. So where do hot springs get their “heat” from?
Answer:
Hot Springs get their “heat” from aquifers deep within the Earth.

51. Hot Springs that erupt are called
Temperature
Of Springs
Groundwater
Systems
Sometimes the groundwater from these aquifers absorb so much heat…..they erupt!
Hot Springs that erupt are called
geysers!

52. Wells Groundwater Systems
The red dashed line represents where the water table used to be before most of the water was pumped out!

53. Wells Groundwater Systems The distance between the deepest part of
the cone of depression and the “old”
Water table line is called drawdown.

54. Wells recharge. Groundwater Systems
Eventually, water from runoff and precipitation is added back to the zone of saturation.
This process is called
recharge.

55. Groundwater
Systems
Confined
Aquifers
Water-table aquifers are often polluted when chemicals spill on surface sediment.

56. Groundwater
Systems
Confined
Aquifers
If an aquifer is located between two aquacludes, it can be protected from pollution.

57. In essence, the aquacludes become “body guards” to the aquifer.
Groundwater
Systems
Confined
Aquifers
In essence, the aquacludes become “body guards” to the aquifer.

58. An aquifer “sandwiched” between two aquacludes is referred to as a
Groundwater
Systems
Confined
Aquifers
An aquifer “sandwiched” between two aquacludes is referred to as a
Confined Aquifer.

59. Groundwater Confined Systems Aquifers
Confined aquifers usually contain water under pressure since the area of “recharge” is at a higher elevation.

60. Groundwater Confined Systems Aquifers
Confined aquifers usually contain water under pressure since the area of “recharge” is at a higher elevation.

61. Groundwater Confined Systems Aquifers
This type of aquifer is called an Artesian aquifer and water that spurts from it is called an Artesian Well.

63. Pollutants from sewage travel downslope to contaminate wells.

64. Protecting Our Water Supply
There are a number of ways in which groundwater resources can be protected and restored.
All major pollution sources need to be identified and eliminated.