1. Water and Water Pollution

5. Dams
A dam is any obstruction placed in a river or stream to block the flow of water so that water can be stored in a reservoir
Large losses
of water through
evaporation
Flooded land destroys forests or cropland and
displaces people
Downstream flooding is reduced
Downstream cropland and
estuaries are deprived of
nutrient-rich silt
Migration and spawning of some fish are disrupted
Provides water
for year-round
irrigation of
cropland
Reservoir is useful for recreation and fishing
Can produce cheap electricity (hydropower)

6. Benefits of Dams Power generation Emissions reduction Crop irrigation
Drinking water
Flood control
Shipping
New recreational opportunities
Hydroelectric dams—inexpensive energy
Provide energy without burning fossil fuels
Reservoir water can be withdrawn for irrigation purposes
Can help to buffer against drought by providing storage
Most reservoirs store water for cities to use
Store seasonal surges (such as after a snow melt) and then can be gradually released
Make it easier for ships to go than on a rocky river
Fishing, boating, etc

7. Costs of dams Habitat alteration Decline in fisheries
Population displacement
Sediment capture
Disruption of flooding
Risk of failure
Lost recreational opportunities
Cause floods and modify river paths
Fish that migrate to spawn may find dams as a barrier (ex) salmon)
Flood farmland, and may force humans to move
As the rivers slow, the sediments in the water settle to the bottom of the river and get trapped in the dam
Floods actually help soil, and dams stop natural flooding—loss of topsoil
Could fail—think xmen
No whitewater rafting, etc

8. Three Gorges Dam
Largest dam in the world—China

9. Three Gorges Damn

10. Aquifers

12. Desalination
This is the removal of salt from seawater or other water of marginal quality

14. Aral Sea case study

18. Oxygen sag curve

19. Groundwater pollution
Coal strip mine runoff
Pumping well
Waste lagoon
Accidental spills
Groundwater flow
Confined aquifer
Discharge
Leakage from faulty casing
Hazardous waste injection well
Pesticides
Gasoline station
Buried gasoline and solvent tank
Sewer
Cesspool septic tank
De-icing road salt
Unconfined freshwater aquifer
Confined freshwater aquifer
Water pumping well
Landfill