The content of this presentation is about how ground water works.

1. Lec 12: Groundwater
Geol 100: Principles of Geology

2. Hydrological
cycle
Lec 12: Groundwater

3. Earth’s water
distribution
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4. Groundwater represents the largest
reservoir of freshwater that is
readily available to humans.
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5. Geological roles
Erosional agent
Streamflow equalizer
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6. Distribution
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Zone of soil moisture/ soil zone: Near
surface zone that wets the surface of
grains and organic material making
up the soil

7. Distribution
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Unsaturated zone: Zone where water
clings toot tightly to the soil, sediment,
and rock

8. Distribution
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Saturation zone: Zone where all of the
open spaces in sediment and rock are
completely filled with water

9. Distribution
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Water table: Upper limit of the zone of
saturation

10. Distribution
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Water table: Shape replicates the
surface and changes depending on
rainwater supply

11. Factors influencing storage
and distribution
Porosity
Permeability
Aquitards and aquifers
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12. Porosity
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Percentage of the total volume of rock
or sediment that consists of pore
spaces that can store groundwater
Voids may be spaces between particles, joints,
faults, cavities in dissolved materials, vesicles

13. Permeability
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Ability of a material to transmit fluid
along connected and large pores

14. Aquitard vs aquifer
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Aquitard Aquifer
Impermeable layers that
hinder or prevent water
movement
Permeable rock strata or
sediments that transmit
groundwater freely
Example: clay Example: sand and gravel

15. Groundwater flow
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• Unsaturated zone: downward movement
due to pull of gravity
• Saturated zone: moves downward,
sideway, upward due to pressure and pull
of gravity

16. Groundwater flow
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Hydraulic head: energyfrom
elevationand pressure which
causes water to flow
groundwater flows from higher
hydraulic head to lower hydraulic head

17. Groundwater flow
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Recharge area: water enters
the ground via downward flow
direction
Dischargearea: water flows
back up to the surface

18. Groundwater
flow factors
1. Complex, crooked network pathway
2. Friction with surrounding rocks
3. Water table slope
4. Material permeability
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19. Obtaining groundwater
Spring: natural outlets from which groundwater flows
Well: holes that people dig or drill
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20. Spring
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Groundwaterflow when water table
intersects the ground surface

21. Spring
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Groundwaterflow when water table
intersects the ground surface

22. Spring: Hot spring
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Formed by:
1. Circulating groundwater at
higher depths
2. Heated water rise to surface
+6 to 9C mean annual air temperature of
the specific area

23. Spring: Geyser
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• Occurs where extensive undergroundchambers
exist within hot igneous rocks
• Formationalprocess:
1. Cool groundwater is heated
2. Heating causes water to expand
3. Water is ejected  lowering pressure
4. Leftover water turns into steam
5. Geyser erupts
6. Extruded water infiltrates the ground
7. Cycle repeats
Ejects water with great force at various intervals
that may release steam

24. Spring: Geyser
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Ejects water with great force at various intervals
that may release steam

25. Well
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Drawdown: depression in the water
table due to continuous well pumping
Hole bored into the zone of saturation where groundwater
moves to the surface

26. Artesian well
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Penetrates confined aquifers in which water is under
enough pressure to rise on its own above the surface of
the aquifer

27. Problems
• Depletion of groundwater supply
• Lowering water table
• Reversingthe flow direction of groundwater
• Saline intrusion
• Pore collapse and land subsidence
• Natural groundwater quality
• Human-cause groundwater contamination
• Unwanted effects of rising water tables
• Groundwater treated as a non-renewable
resource
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28. Lec 12: Groundwater
Lowering of water table and reversing the
flow direction of groundwater
Saline intrusion

29. Lec 12: Groundwater
Pore collapse and land subsidence

30. Problems
• Depletion of groundwater supply
• Lowering water table
• Reversingthe flow direction of groundwater
• Saline intrusion
• Pore collapse and land subsidence
• Natural groundwater quality
• Human-cause groundwater contamination
• Unwanted effects of rising water tables
• Groundwater treated as a non-renewable
resource
Lec 12: Groundwater

31. Groundwater
landforms
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Caverns: formed due to groundwater
erosion
Karst topography:formed due to
groundwater dissolution

32. Cavern
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1. Acidic water follows rock weaknesses
2. Dissolvessurroundingrocks
3. Cavities grow forming caverns
4. Dissolvedmaterials flow to streams and
oceans
Created at or below the water table in the zone of saturation

33. Travertine
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• Stalactites: hanging from the ceiling
of the cavern formed where water
seeps through cracks above
• Stalagmites: develops on the floor of
a cavern reaching to the ceiling
Calcium carbonate left by endless dripping of water of
caverns above the water table in the unsaturated zone

34. Travertine
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• Stalactites: hanging from the ceiling
of the cavern formed where water
seeps through cracks above
• Stalagmites: develops on the floor of
a cavern reaching to the ceiling
Calcium carbonate left by endless dripping of water of
caverns above the water table in the unsaturated zone

35. Karst topography: sinkhole
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Irregular depressions
common in karst areas

36. Karst topography: sinkhole
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37. Karst topography: sinkhole formation
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38. Karst topography: sinkhole formation
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39. Karst topography: tower karst
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• Isolated steep sided hills that
rise abruptly from the ground
• Rapid karst developmentin
tropical climates due to abundant
rainfall and greater availability of
carbon dioxide

40. Karst topography: tower karst
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• Isolated steep sided hills that
rise abruptly from the ground
• Rapid karst developmentin
tropical climates due to abundant
rainfall and greater availability of
carbon dioxide

41. Questions?
Lec 12: Groundwater