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Water. Chapter 15. Water Wars. Water shortage Growing population Poor irrigation efficiency Economic competition- importing more grain to reduce need for irrigation water or work out water-sharing agreements with other countries. Unique Properties of Water. Strong hydrogen bonds

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Chapter 15

Water Wars

  • Water shortage

  • Growing population

  • Poor irrigation efficiency

  • Economic competition- importing more grain to reduce need for irrigation water or work out water-sharing agreements with other countries

Unique Properties of Water

  • Strong hydrogen bonds

  • Liquid over wide temperature range

  • High heat capacity – changes temperature slowly (moderates climate, used as coolant for car engine & power plants)

  • Large amount of energy needed to evaporate – heat is then released during condensation (helps distribute heat & determine climate zones; evaporation/sweating = cooling process)

  • Dissolves many substances- dissolves nutrients in living tissue, flush waste out of tissues, all-purpose cleanser, helps remove/dilute water-soluble waste

  • Filters out UV radiation that would harm aquatic organisms

  • Bonds – allow capillary action – water can move upward through plants

  • Expands when frozen= ice floats; prevents lakes & streams from freezing solid

Available Freshwater

  • Only 0.014% is available for useh

Water Cycle

  • Surface runoff- water flowing off the land into bodies of surface water

  • Reliable runoff- amount of run-off that we can generally count on as a stable source of water

  • Watershed (drainage basin)- region from which surface water drains into a river, lake, wetland, or other body of water

  • Groundwater- water stored in spaces in soil & rock

  • Zone of aeration- close to surface; pore space contains mixture of air & water

  • Zone of saturation- lower layers of soil where pore space is filled with water

  • Water table- top of zone of saturation

  • Aquifer- (deep) porous, water-saturated layers of sand, gravel, or bedrock through which groundwater flows

  • Natural recharge- natural replenishment of an aquifer by precipitation, which percolates downward through soil & rock

  • Shortages result from:

  • Removing groundwater faster than it is replenished

  • Some aquifers receive little, if any recharge

Water Use

  • Withdrawal- total amount of water removed from lake, river, or aquifer for any purpose

  • Consumptive water use- withdrawn water is not available for reuse in basin due to losses like evaporation, seepage into ground, transportation to another area, or contamination

Water Use

  • Population- up 3x

  • Global water withdrawal- up 7x

  • Per capita withdrawal- up 4x

  • Reliable surface runoff used- 34%

  • Used by 2025- 70% (90% if per capita rises too)

  • Irrigation- 70%

  • Industry- 20%

  • Residences & cities- 10%

Eastern U.S.

  • Major water use- energy production, cooling, & manufacturing

  • Problems- flooding, occasional urban shortages, pollution

Western U.S.

  • Major water use- irrigation

  • Problems- shortage of runoff, low precipitation / high evaporation, recurring prolonged drought

Causes of Water Scarcity

  • Dry climate

  • Drought- prolonged period with 70% less precipitation & higher than normal evaporation

  • Dessication- drying of exposed soil due to deforestation or overgrazing

  • Water stress- low per capita availability due to high population relying on limited runoff

Increase Freshwater Supply

  • Build dams & reservoirs to store runoff

  • Bring in surface water from another area

  • Desalinization

  • Reduce water waste

  • Import food to reduce water use in crops & cattle

  • Withdraw groundwater

Government Ownership

- Poor management & efficiency

+ Strict government oversight

+ Equal access & fair rates

Private Ownership

+ Funds & management expertise

+ Improved efficiency, good job

- No rate control

- Profitable

- Sold as a luxary, not basic need

Figure 15-9Page 313


cropland and

estuaries are

deprived of

nutrient-rich silt

Flooded land

destroys forests

or cropland and

displaces people

Large losses

of water through



flooding is


Provides water

for year-round

irrigation of


Reservoir is

useful for


and fishing

Can produce

cheap electricity


Migration and

spawning of

some fish are


Colorado River Dams

+ Provides electricity from numerous hydroelectric plants

+ Provides water for 7 states

+ Multibillion dollar recreational industry (whitewater rafting, boating, fishing, camping, hiking)

- Arid area

- Legal pacts allocating water supply for US & Mexico

- River water rarely makes it to Guld of California

- Threatens aquatic spawning

- Destroys estuaries

- Increases saltwater contaminated coastal aquifers


China’s Three Gorges Dam



Will generate about 10%

of China’s electricity

Reduces dependence

on coal

Reduces air pollution

Reduces CO2 emissions

Reduces chances of

downstream flooding

for 15 million people

Reduces river sitting

below dam by eroded


Increases irrigation water

for cropland below


Floods large areas of

cropland and forests

Displaces 1.9 million people

Increases water pollution

because of reduced water


Reduces deposits of nutrient-

rich sediments below dam

Increases saltwater

Introduced into drinking water

near mouth of river because

of decreased water flow

Disrupts spawning and

migration of some fish

below dam

High cost

Figure 15-11Page 315

Aral Sea Water Transfer Project

  • Shrinking of Aral Sea

  • Regional ecological, economic, health disaster

  • Salinity 3x higher

  • Surface area down 58%

  • 83% water loss

  • Feeder rivers reduced to trickles

  • Eliminates wetlands

  • Birds & mammal species disappeared

  • Extinction of 20 (of 24) native fish species

  • Salt dust settles on wildlife, crops, & other vegetation


Degrade Sacramento River

Threatens fisheries

Reduces flushing of San Francisco Bay pollutants

Water sent South is wasted


Need more water to grow crops

Lakes shrink = reduced populations of ducks, gulls, & wading birds

California Water Transfer Project

James Bay in Canada

- 600 dams & dikes that will reverse or alter flow of 19 giant rivers

- Will flood boreal forests & tundra

- Displace of indigenous Cree & Inuits

+ Hydroelectric power


Withdrawing Groundwater



Aquifier depletion from over-


Sinking of land (subsidence)

when water removed

Polluted aquifiers unusable

for decades or centuries

Saltwater intrusion into

drinking water supplies near

coastal areas

Reduced water flows into

streams, lakes, estuaries,

and wetlands

Increased cost, energy use,

and contamination from

deeper wells

Good source of water for

drinking and irrigation

Available year-round

Exists almost everywhere

Renewable if not over-

pumped or contaminated

No evaporation losses

Cheaper to extract than

most surface waters

Figure 15-15Page 319

Excessive Withdrawal

  • Unsustainable water mining

  • Limits future food production

  • Increases gap between rich & poor areas

  • Must drill deeper wells, buy larger pumps, & use more electricity

  • Causes sinkholes

Saltwater Intrusion

  • Movement of salt water into freshwater aquifers in coastal & inland areas as groundwater is withdrawn faster than it is recharged by precipitation

  • Groundwater becomes unusable

Ogallala Aquifer

+ Transformed vast areas of arid prairie into productive agricultural land

- Slows recharge rate

- Aquifer is thinner for southern region

- Government subsidies increased crop production & increases depletion of aquifer


Groundwater Depletion



Raise price of water to

discourage waste

Tax water pumped

from Wells near

surface water

Set and enforce

minimum stream flow


Waste less water

Subsidize water


Ban new wells in

aquifiers near surface


Buy and retire ground-

water withdrawal rights in

critical areas

Do not grow water-

intensive crops in dry


Reduce birth rates

Figure 15-18Page 320

Deep Aquifer Concerns:

  • Little known about geological & ecological impacts of using these aquifers

  • No international water treaties govern the rights to & ownership of water that underlies several countries


- High cost

- Large energy requirements

- Large amounts of briny waste water

- Dumping of waste increases salinity of ocean water (food resources & aquatic life threatened)

+ Make ocean water or brackish water usable

Seeding Clouds

  • Does not work well in very dry areas

  • No scientific evidence of success

  • Introduces large amounts of chemicals into soil & water systems (harms people, wildlife, & agricultural productivity)

  • Ownership of cloud water

Iceberg Towing

  • Unsure methods

  • Cost

  • Probably neither (iceberg towing or cloud seeding) would provide significant amounts of freshwater

Wasted Water

  • 65-70% of world water is wasted

  • Could be reduced to 15%

  • Causes:

  • Underpricing- government subsidies for irrigation water, electricity, & diesel fuel for farmers to pump water at below-market price

  • Lack of government subsidies for improving efficiency of water use

Irrigation Systems

  • Center pivot- uses pump to spray water on crops

    • 80% efficient

    • Uses 25% less water

  • Drip irrigation- microirrigation- above or below ground pipes or tubes deliver water to individual plant roots

    • 90-95% efficient

  • Gravity flow- water flow into ditches from aqueduct or nearby river

    • 60-80% efficient

Figure 15-20Page 324

Center Pivot

(efficiency 80% with low-pressure

sprinkler and 90–95% with

LEPA sprinkler)

Water usually pumped from

underground and sprayed from

mobile boom with sprinklers.

Drip Irrigation

(efficiency 90-95%)

Above- or below-ground pipes

or tubes deliver water to

individual plant roots.

Gravity Flow

(efficiency 60% and 80% with surge valves)

Water usually comes from an

aqueduct system or a nearby river.


Reducing Irrigation Water Waste

  • Lining canals bring water to irrigation ditches

  • Leveling fields with lasers

  • Irrigating at night to reduce evaporation

  • Using soil and satellite sensorsand computer systems to monitor soil moisture and add water only when necessary

  • Polyculture

  • Organic Farming

  • Growing water-efficient crops using drought-resistant and salt tolerant crops varieties

  • Irrigating with treated urban waste water

  • Importing water-intensive crops and meat

Figure 15-21Page 324


Reducing Water Waste

  • Redesign manufacturing processes

  • Landscape yards with plants that require little water

  • Use drip irrigation

  • Fix water leaks

  • Use water meters and charge for all municipal water use

  • Use waterless composting toilets

  • Require water conservation in water-short cities

  • Use water-saving toilets, showerheads, and front-loading clothes washers

  • Collect and reuse household water to irrigate lawns and nonedible plants

  • Purify and reuse water for houses, apartments, and office buildings

Figure 15-22Page 325

Reducing Water Used to Remove Waste

  • Use pollution prevention & waste reduction to decrease waste production

  • Ban toxic wastes in municipal sewer system

  • Waterless composting toilet

  • Nutrient-rich sludge returned to soil as fertilizer

  • New sewage treatment methods that recycle nutrients in organic waste material


+ Fertile soils

+ Ample water for irrigation

+ Rivers for transportation & recreation

+ Flat land suitable for crops, buildings, highways, & railroads

- Removal of water-absorbing vegetation

Increasing Flood Damage

  • Removal of water-absorbing vegetation

  • Draining wetlands

  • Living on floodplains

  • Pavement & buildings


  • Straighten & deep streams

  • Build levees or floodwalls

  • Build dams

  • Preserve existing wetlands & restore degraded wetlands

  • Identify & manage flood-prone areas

  • Think carefully about where we live

Figure 15-26Page 329


Sustainable Water Use

  • Not depleting aquifers

  • Preserving ecological health of aquatic systems

  • Preserving water quality

  • Integrated watershed management

  • Agreements among regions and countries sharing surface water resources

  • Outside party mediation of water disputes between nations

  • Marketing of water rights

  • Raising water prices

  • Wasting less water

  • Decreasing government subsides for supplying water

  • Increasing government subsides for reducing water waste

  • Slowing population growth

Figure 15-27Page 330

What Can You Do?

Water Use and Waste

  • Use water-saving toilets, showerheads, and faucet aerators

  • Shower instead of taking baths, and take short showers.

  • Repair water leaks.

  • Turn off sink faucets while brushing teeth, shaving, or washing.

  • Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads.

  • Wash a car from a bucket of soapy water, and use the hose for rinsing only.

  • If you use a commercial car wash, try to find one that recycles its water.

  • Replace your lawn with native plants that need little if any watering.

  • Water lawns and garden in the early morning or evening.

  • Use drip irrigation and mulch for gardens and flowerbeds.

  • Use recycled (gray) water for watering lawns and houseplants and for washing cars.

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