Transcript APES Chapter 14

APES Chapter 14
• Water Resources
Water’s Unique Properties
 Hydrogen bonding
 Liquid over wide temperature range
 Changes temperature slowly
 High heat of evaporation
 Great dissolving power
 Helps regulate pH
 Adhesion and cohesion
 Expands when it freezes
ALL Because it’s POLAR
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Supply of Water Resources
Freshwater
Readily accessible freshwater
Groundwater
0.592%
Biota
0.0001%
Lakes
0.0007%
Ice caps
and glaciers
1.984%
0.014%
Fig. 14-2 p. 314
Soil
moisture
0.0005%
Rivers
0.0001%
Atmospheric
water vapor
0.0001%
What is Surface Water?
• Precipitation that does not infiltrate the
ground or return to the atmosphere by
evaporation.
– Example: A watershed (drainage basin) is a
region from which water drains into a stream,
lake, reservoir, wetland, or other body of
water.
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What is Groundwater?
• Precipitation that infiltrates into the ground
and percolates downward through spaces
between soil and rock.
– Near the surface, these voids contain little
moisture.
– Deeper, in the zone of saturation, the voids
are completely filled with water.
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• The water table is located at the top of the zone
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of saturation.
Porous, water-saturated layers of sand, gravel ,
or rock are called aquifers.
An area of land through which water passed
downward into an aquifer is the recharge area.
If water is withdrawn from an aquifer faster than
it can recharge the aquifer will become depleted.
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Ground Water
Fig. 14-3 p. 315
Flowing
artesian well
Precipitation
Well requiring a pump
Evaporation and transpiration
Evaporation
Confined
Recharge Area
Runoff
Aquifer
Infiltration
Stream
Water table
Lake
Infiltration
Unconfined aquifer
Less permeable material
such as clay
Confined aquifer
Confirming permeable rock layer
Use of Water Resources
 Humans use about 50% of reliable runoff
 Agriculture
 Industry
 Domestic
United States
Power
cooling
38%
Agriculture
38%
 Power plants
Fig. 14-5 p. 316
Industry 11%
Public 10%
What causes freshwater
shortages?

Dry climate

Drought

Desiccation
Acute shortage

Adequate supply
Water stress
Shortage
Fig. 14-7 p. 317
Metropolitan regions with population
greater than 1 million
How can we increase
Freshwater Supplies?
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Build dams and reservoirs
Bring in water from another area
Withdraw groundwater
Waste less water
Import food to reduce water use
Building Dams
Advantages
• Control flooding
• Produce hydroelectric
power
• Supply water for towns
and cities
• Provide recreational
activities such as fishing
and boating
Disadvantages
• Large water loss through
evaporation
• Land lost
• Migration and spawning
of some fish disrupted
• No nutrient-rich silt
downstream of dam
Using Dams and Reservoirs to Supply
More Water
Downstream cropland and
estuaries are deprived of
nutrient-rich silt
Flooded land destroys
forests or cropland and
displaces people
Large losses
of water through
evaporation
Downstream flooding is
reduced
Reservoir is useful for
recreation and fishing
Can produce cheap electricity (hydropower)
Fig. 14-9 p. 319
Migration and spawning of some fish are disrupted
Provides water
for year-round
irrigation of
cropland
Transferring water form another
area
Advantages
• Supplies water for
agricultural, domestic,
and industrial needs
Disadvantages
• Degrade rivers
• Deplete groundwater
• Threaten fisheries
Tapping Groundwater
Advantages
• Year round supply
• Not lost by evaporation
• Less expensive to
develop than surface
water sources
Disadvantages
• Water table lowering
• Aquifer depletion
• Intrusion of salt water into
aquifers
• Reduce stream flow
• May be contaminated by
septic tanks or industrial
activities
Desalination
Advantages
• Can provide fresh water
from very abundant salt
water
Disadvantages
• Very expensive
• Produces large quantities
of wastewater
How Can We Use Water More
Efficiently?
 Reduce losses due to leakage
 Reform water laws
 Improve irrigation efficiency (Fig. 14-18 p. 330)
 Improving manufacturing processes
 Water efficient landscaping
 Water efficient appliances
Too Much Water: Floods
 Natural phenomena
 Aggravated by
human
activities
 Renew and replenish
Reservoir
Dam
Levee
Flood
wall
Floodplain
Fig. 14-22 p. 332
Solutions: Achieving a More
Sustainable Water Future
Efficient irrigation
Water-saving technologies
Improving water management
See Fig. 14-25 p. 336