Water and Water PollutionWater and Water Pollution

DamsDams• A A damdam is any obstruction placed in a is any obstruction placed in a

river or stream to block the flow of river or stream to block the flow of water so that water can be stored in water so that water can be stored in a reservoira reservoir

Reservoir is useful for recreation and fishing

Can produce cheap electricity (hydropower)

Large lossesof water throughevaporation

Large lossesof water throughevaporation

Flooded land destroys forests or cropland anddisplaces people

Flooded land destroys forests or cropland anddisplaces people

Downstream flooding is reduced

Downstream flooding is reduced

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Migration and spawning of some fish are disruptedMigration and spawning of some fish are disrupted

Provides waterfor year-roundirrigation ofcropland

Benefits of DamsBenefits of Dams1.1. Power generationPower generation

2.2. Emissions reductionEmissions reduction

3.3. Crop irrigationCrop irrigation

4.4. Drinking waterDrinking water

5.5. Flood controlFlood control

6.6. ShippingShipping

7.7. New recreational opportunitiesNew recreational opportunities

Costs of damsCosts of dams

1.1. Habitat alterationHabitat alteration

2.2. Decline in fisheriesDecline in fisheries

3.3. Population displacementPopulation displacement

4.4. Sediment captureSediment capture

5.5. Disruption of floodingDisruption of flooding

6.6. Risk of failureRisk of failure

7.7. Lost recreational opportunitiesLost recreational opportunities

Three Gorges DamThree Gorges Dam• Largest dam in the world—ChinaLargest dam in the world—China

Three Gorges DamnThree Gorges Damn

AquifersAquifers

DesalinationDesalination• This is the removal of salt from This is the removal of salt from

seawater or other water of marginal seawater or other water of marginal qualityquality

Aral Sea case studyAral Sea case study

Oxygen sag curve

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