1. Chapter 11 – WATER UNDER THE GROUND

2. Freshwater Underground
Ground water
Subsurface water contained in pore spaces in regolith & bedrock

3. Freshwater Underground
Zone of aeration
Mix of air & water
Zone of saturation
Saturated with water
Water table
Top of saturated zone

4. Freshwater Underground
How groundwater moves
Porosity
% of total volume of rock body or regolith made of open spaces (pores)
Permeability
Measure of how easily a solid allows fluids to pass through it

5. Freshwater Underground
How groundwater moves
Hydraulic gradient
Change in elevation divided by distance
Used to determine rate of groundwater flow

6. Freshwater Underground
How groundwater moves (continued)
Percolation
Groundwater seeps downward
Recharge
Replenishment of groundwater
Discharge
Subsurface water leaves saturated zone
Becomes surface water
Spring
Occurs where water table intersects land surface

7. Freshwater Underground
How groundwater moves (continued)
Other methods of discharge
Hot springs
Geysers

8. Freshwater Underground
Where groundwater is stored
Aquifer
Rock body or regolith that is water saturated, porous, & permeable
Aquiclude
Layer of impermeable rock

9. Freshwater Underground
Where groundwater is stored
Aquifer
Unconfined
Confined
Potentiometric surface
Artesian well

10. Freshwater Underground
Groundwater depletion
Cone of depression
Cone-shaped dip in water table due to pumping
Groundwater mining
Rates of groundwater withdrawal continuously exceed rate of recharge

11. Freshwater Underground
Groundwater depletion (continued)
Land subsidence
Compaction
Salt water intrusion

12. Freshwater Underground
Groundwater contamination
Contamination

13. Freshwater Underground
Dealing with groundwater issues
Enhanced recharge
Conservation
Other sources
Desalination (i.e. distillation; reverse osmosis; electrolysis)
Icebergs

14. Freshwater Underground
Natural methods
Filtration
Decomposition
Bacterial action
Human methods
Exterior treatments
Dilution
Chemical treatments

15. Groundwater in the U.S.

16. Groundwater in the U.S. Groundwater Mining
Recharge rate vs. consumption rate
Ogallala Aquifer: largest aquifer in U.S.
225,000 sq miles
Found in 8 states
30,000 years of water accumulation

17. Ogallala Aquifer

18. Groundwater in Nebraska

19. Groundwater in Nebraska

20. Groundwater in Nebraska
What areas seem best suited for groundwater withdrawal?
Why do you think these areas are not utilized?
Answer: The Nebraska Sandhills
However, Crops do not grow well in sand, so the area is primarily used for ranching.

21. Freshwater Underground
When groundwater dissolves rock
Carbon dioxide + water = carbonic acid
Adds acid to water in atmosphere & underground
Calcite + carbonic acid = dissolution
Calcite dissolves

22. Freshwater Underground
Factors of dissolution
Rock composition
Extent of rock fracturing, jointing, & bedding
Acidity of water
Climate

23. Freshwater Underground
When groundwater dissolves rock
Karst topography
Sinkholes
Disappearing streams

24. Freshwater Underground
When groundwater dissolves rock
Cave
Underground open space
Cavern = system of connected caves
Stalactites
Stalagmites
Columns (pillars)