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 Expands when it freezes

ALL Because it’s POLAR

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Supply of Water Resources

Fig. 14-2 p. 314Fig. 14-2 p. 314

FreshwaterFreshwater Readily accessible freshwaterReadily accessible freshwater

Biota0.0001%

Biota0.0001%

Rivers0.0001%Rivers

0.0001%

Atmosphericwater vapor

0.0001%

Atmosphericwater vapor

0.0001%

Lakes0.0007%

Soilmoisture0.0005%

Groundwater0.592%

Groundwater0.592%

Ice capsand glaciers

1.984%

0.014%0.014%

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 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• If water is withdrawn from an aquifer faster than it can recharge the aquifer will become depleted.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

Evaporation and transpiration

Evaporation

Stream

Infiltration

Water tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay Confirming permeable rock layer

Fig. 14-3 p. 315Fig. 14-3 p. 315

Use of Water Resources

Humans use about 50% of reliable runoff

Agriculture

Industry

Domestic

Power plants

Fig. 14-5 p. 316Fig. 14-5 p. 316

United States

Industry 11%

Public 10%

Powercooling

38%

Agriculture38%

What causes freshwater shortages?

Dry climate

Drought

Desiccation

Water stress

Acute shortage

Adequate supply

Shortage

Metropolitan regions with population greater than 1 millionFig. 14-7 p. 317Fig. 14-7 p. 317

How can we increase Freshwater Supplies?

• 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

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 reducedDownstream flooding is reduced

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Downstream cropland andestuaries are deprived ofnutrient-rich silt

Reservoir is useful for recreation and fishing

Can produce cheap electricity (hydropower)

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

Provides waterfor year-roundirrigation ofcropland

Fig. 14-9 p. 319Fig. 14-9 p. 319

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

Floodplain

Levee Floodwall

Dam

Reservoir

Renew and replenish

Aggravated by human activities

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. 336See Fig. 14-25 p. 336