chapter 14 water water. chapter overview questions why is water so important, how much freshwater is...

Chapter 14Chapter 14

WaterWater

Water

Chapter Overview QuestionsChapter Overview Questions

Why is water so important, how much Why is water so important, how much freshwater is freshwater is availableavailable to us, and how much to us, and how much of it are we of it are we usingusing??

What causes What causes freshwater shortagesfreshwater shortages, and what , and what can be done about this problem?can be done about this problem?

What are the advantages and disadvantages What are the advantages and disadvantages of of withdrawing groundwaterwithdrawing groundwater??

What are the advantages and disadvantages What are the advantages and disadvantages of using of using dams and reservoirsdams and reservoirs to supply more to supply more water?water?

Chapter Overview Questions (cont’d)Chapter Overview Questions (cont’d)

What are the advantages and disadvantages What are the advantages and disadvantages of of transferring large amounts of watertransferring large amounts of water from from one place to another?one place to another?

Can Can removing saltremoving salt from seawater solve our from seawater solve our water supply problems?water supply problems?

How can we How can we waste lesswaste less water? water? How can we How can we useuse the earth’s water more the earth’s water more

sustainablysustainably?? What causes What causes floodingflooding, and what can we do , and what can we do

about it?about it?

Core Case Study: Water Conflicts in Core Case Study: Water Conflicts in the Middle East - A Preview the Middle East - A Preview

of the Futureof the Future

Many countries in Many countries in the the Middle EastMiddle East, , which has one of which has one of the the world’s highest world’s highest population growthpopulation growth rates, face water rates, face water shortages.shortages.

Figure 14-1Figure 14-1

Figure 14-1Figure 14-1

Water Conflicts in the Middle East: A Water Conflicts in the Middle East: A Preview of the FuturePreview of the Future

Most water in this dry region comes from the Most water in this dry region comes from the Nile, Jordan or TigrisNile, Jordan or Tigris rivers. rivers.

Countries are in Countries are in disagreementdisagreement as to who has as to who has water rights, but there are some agreements.water rights, but there are some agreements.

Currently, there are Currently, there are no cooperative no cooperative agreementsagreements for use of for use of 158 of the world’s 263158 of the world’s 263 water basins that are shared by two or more water basins that are shared by two or more countries.countries.

Nile River- Nile River- 97% of Egypt’s 97% of Egypt’s

freshwater freshwater Shared by Shared by

Ethiopia, Ethiopia, Sudan, & EgyptSudan, & Egypt

Jordan River- Jordan River- Shared by Shared by Syria, Jordan, Palestine Syria, Jordan, Palestine (Gaza & West Bank), & (Gaza & West Bank), & IsraelIsrael

Syria pop. will double by Syria pop. will double by 20502050

Syria plans to build dams Syria plans to build dams and withdraw more waterand withdraw more water

Israel does cooperate Israel does cooperate with Jordan & Palestinewith Jordan & Palestine

Water Conflicts in the Middle East?Water Conflicts in the Middle East? TigrisTigris & Euphrates Rivers-& Euphrates Rivers- Shared by Turkey, Shared by Turkey,

Syria, & Iraq.Syria, & Iraq.

Figure 14-1Figure 14-1

WATER’S IMPORTANCE, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAVAILABILITY, AND RENEWAL

Water keeps us alive, moderates climate, Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes sculpts the land, removes and dilutes wastes and pollutants, and moves continually and pollutants, and moves continually through the hydrologic cycle.through the hydrologic cycle.

71%71% of Earth’s surface is covered with water of Earth’s surface is covered with water Only about Only about 0.024%0.024% of the earth’s water of the earth’s water

supply is available to us as liquid freshwatersupply is available to us as liquid freshwater Why is this number so low?Why is this number so low?

WATER’S IMPORTANCE, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAVAILABILITY, AND RENEWAL

Comparison of Comparison of population sizes and population sizes and shares of the world’s shares of the world’s freshwater among freshwater among the continents.the continents.

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Fig. 14-2, p. 307

ContinentPercent of world's water resources and population

Asia60.5%

36%

Africa10%

8%Europe

North and Central America 7.3%

South America and Caribbean 6.4%

26%

15%

5%Oceania

11.3%

0.5%

14%

WATER’S IMPORTANCE, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAVAILABILITY, AND RENEWAL

Some precipitation Some precipitation infiltratesinfiltrates the ground and the ground and is stored in soil and rockis stored in soil and rock (groundwater (groundwater).).

Water that does not sink into the ground or Water that does not sink into the ground or evaporate into the air evaporate into the air runs offruns off ( (surface runoffsurface runoff) ) into into bodies of waterbodies of water.. The land from which the surface water drains into The land from which the surface water drains into

a body of water is called its a body of water is called its watershedwatershed or or drainage basindrainage basin..

Ground WaterGround WaterA simplified

surficial aquifer

Coastal Georgia:

-a few feet down

-“sulfur water”

Zone of saturation

Water Table

Fig. 14-3, p. 308

Unconfined Aquifer Recharge Area

Precipitation Evaporation and transpiration Evaporation

Confined Recharge Area

Runoff

Flowing artesian well

Recharge Recharge Unconfined Unconfined AquiferAquifer

Stream Well requiring a pumpInfiltration Water

table LakeInfiltration

Unconfined aquifer

Confined aquiferConfining impermeable rock layer Confining impermeable rock layer

Less permeable Less permeable material such as claymaterial such as clay

Ground Water: Floridan AquiferGround Water: Floridan Aquifer

Ground Water: SpringsGround Water: Springs

Ground Water: Artesian WellsGround Water: Artesian Wells

Bogue Chitto River, LA

Jasper, SC

Ground Water: Artesian WellsGround Water: Artesian Wells

ga.water.usgs.gov/edu/gwartesian.html

The diagram below shows the aquifer system near Brunswick, Georgia, as it was before development of the Floridan aquifer system in the 1880’s. The aquifer system was under artesian conditions and the pressure in the aquifer system was great enough that wells flowed at land surface throughout most of the coastal area. In some areas, pressure was high enough to elevate water to multi-story buildings without pumping. The artesian water level (potentiometric surface) was about 65 feet above sea level at Brunswick. Ground water discharged naturally to springs, rivers, ponds, wetlands, and other surface-water bodies and to the Atlantic Ocean. Nowadays, ground-water pumping has caused the water level in the aquifer to decline throughout the entire coastal area, with the result that some artesian aquifers no longer have enough pressure to cause a well to naturally flow to the land surface.

Ground Water: Artesian WellsGround Water: Artesian Wells

ga.water.usgs.gov/edu/gwartesian.html

Ground Water: Ground Water: Overpumping (overdrafting)Overpumping (overdrafting)

Note: The Floridan Aquifer (500-600 feet below Brunswick) has two saltwater intrusion plumes, one from the ocean and one from an ancient saltwater aquifer that underlies it (not shown in the diagram)

Ground Water: Artesian WellsGround Water: Artesian Wells

During October 2002, the Durango Paper Company (formerly Gillman Paper Company) in St. Marys, Georgia, shutdown paper-mill operations; the shutdown resulted in decreased ground-water withdrawal in Camden County by 35.6 million gallons per day. The decrease in withdrawal resulted in water-level rise in wells completed in the Floridan aquifer system and the overlying surficial and Brunswick aquifer systems; many wells in the St. Marys area flowed for the first time since the mill began operations during 1941. pubs.usgs.gov/sir/2004/5295/

WATER’S IMPORTANCE, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAVAILABILITY, AND RENEWAL

We currently use We currently use more than halfmore than half of the of the world’s reliable runoff of surface water and world’s reliable runoff of surface water and could be using 70-90% by 2025could be using 70-90% by 2025..

IrrigationIrrigation is the biggest user of water is the biggest user of water (70%),(70%), followed by followed by industries (20%) industries (20%) and cities and and cities and residences (10%).residences (10%).

Water in the Water in the United StatesUnited States

Average Average precipitation (top) precipitation (top) in relation to in relation to water-deficit water-deficit regions and their regions and their proximity to proximity to metropolitan areas metropolitan areas (bottom).(bottom).

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Fig. 14-4a, p. 309

Average annual precipitation (centimeters)

More than 122

Less than 41 81–122

41–81

Fig. 14-4b, p. 309

Acute shortage

Metropolitan regions with population greater than 1 million

Shortage

Adequate supply

Case Study: Freshwater Resources in Case Study: Freshwater Resources in the United Statesthe United States

17 western states 17 western states by 2025 could face by 2025 could face intense conflict over intense conflict over scarce water scarce water needed for… needed for… Urban growthUrban growth IrrigationIrrigation RecreationRecreation Wildlife.Wildlife.

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Fig. 14-5, p. 310

Wash.

MontanaOregon

N.D.

IdahoWyoming S.D.

Nevada Neb.

UtahColo.

Kansas

California Oak.

N.M.Texas

Highly likely conflict potential

Moderate conflict potentialUnmet rural water needs

Substantial conflict potential

TOO LITTLE FRESHWATERTOO LITTLE FRESHWATER

About 41% of the world’s population lives in About 41% of the world’s population lives in river basins that do not have enough river basins that do not have enough freshwater.freshwater.

Many parts of the world are experiencing:Many parts of the world are experiencing: Rivers Rivers running dry.running dry. Lakes and seasLakes and seas shrinking. shrinking. Falling water tablesFalling water tables from overpumped aquifers. from overpumped aquifers.

Stress on the World’s River BasinsStress on the World’s River Basins

Comparison of the amount of water available Comparison of the amount of water available with the amount used by humans.with the amount used by humans.

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Fig. 14-6, p. 311

Europe

North America Asia

Africa

South America

Australia

Stress

High None

Water available vs water used

Case Study: Who Should Own and Case Study: Who Should Own and Manage Freshwater ResourcesManage Freshwater Resources

Most water is currently controlled by Most water is currently controlled by governments.governments.

There is controversy over whether water supplies There is controversy over whether water supplies should be owned and managed by should be owned and managed by governmentsgovernments or by or by private corporationsprivate corporations..

Two large French companiesTwo large French companies (Veolia & Suez) (Veolia & Suez) aim to control aim to control 70% of the U.S. water supply70% of the U.S. water supply by by buying up water companies and entering into buying up water companies and entering into agreements with cities to manage water supplies.agreements with cities to manage water supplies.

How Would You Vote?How Would You Vote?Should private companies own or manage most of the Should private companies own or manage most of the world's water resources?world's water resources? a. No.a. No. Democratically elected governments, which are Democratically elected governments, which are

accountable to the voters, should own and manage water accountable to the voters, should own and manage water resources. The profit motive is too high to trust these resources. The profit motive is too high to trust these companies.companies.

b. Qualified yes.b. Qualified yes. Governments should own the water, but Governments should own the water, but expert private companies should manage it.expert private companies should manage it.

c. Depends.c. Depends. Each case must be decided independently. The Each case must be decided independently. The record on private versus public ownership is mixed.record on private versus public ownership is mixed.

d. Yes.d. Yes. Private companies have more expertise and Private companies have more expertise and experience in managing water resources than most experience in managing water resources than most government bureaucrats. government bureaucrats.

TOO LITTLE FRESHWATERTOO LITTLE FRESHWATER

Cities are Cities are outbidding farmersoutbidding farmers for water for water supplies from rivers and aquifers.supplies from rivers and aquifers.

Countries are Countries are importing grainimporting grain as a way to as a way to reduce their water use.reduce their water use.

More crops are being used to produce More crops are being used to produce biofuels.biofuels.

We have three options regarding water in the We have three options regarding water in the future:future:

TOO LITTLE FRESHWATERTOO LITTLE FRESHWATER

Our water options are:Our water options are:

Get moreGet more water from aquifers, rivers, & lakes water from aquifers, rivers, & lakes

DesalinateDesalinate ocean water ocean water

Waste lessWaste less water. water.

WITHDRAWING GROUNDWATER WITHDRAWING GROUNDWATER TO INCREASE SUPPLIESTO INCREASE SUPPLIES

Most aquifers are Most aquifers are renewable resourcesrenewable resources unless water is unless water is removed fasterremoved faster than it is than it is replenished or if they are replenished or if they are contaminated.contaminated.

Groundwater depletionGroundwater depletion is a growing problem is a growing problem mostly from mostly from irrigationirrigation..

Globally, we are currently withdrawing Globally, we are currently withdrawing groundwater groundwater 4x 4x faster than it is recharged.faster than it is recharged. At least one-fourth of the farms in India are being At least one-fourth of the farms in India are being

irrigated from overpumped aquifers.irrigated from overpumped aquifers.

Fig. 14-7, p. 313

Trade-Offs

Withdrawing Groundwater

Advantages Disadvantages

Useful for drinking and irrigation

Aquifer depletion from overpumping

Available year-round

Sinking of land (subsidence) from overpumping

Exists almost everywhere

Polluted aquifers for decades or centuries

Renewable if not overpumped or contaminated

Saltwater intrusion into drinking water supplies near coastal areas

Reduced water flows into surface waters

No evaporation losses

Cheaper to extract than most surface waters

Increased cost and contamination from deeper wells

Groundwater Depletion: Groundwater Depletion: A Growing ProblemA Growing Problem

The Ogallala, the world’s largest aquifer, is most of The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).the red area in the center (Midwest).

The Ogallala is essentially a The Ogallala is essentially a non-renewablenon-renewable aquifer. aquifer.

Areas of Areas of greatest aquifer greatest aquifer depletion from depletion from groundwater groundwater overdraftoverdraft in the in the continental U.S.continental U.S.

Figure 14-8Figure 14-8

Fig. 14-8, p. 314

Groundwater Overdrafts:

High

Moderate

Minor or none

Fig. 14-11, p. 315

Major irrigation well

Well contaminated with saltwater

Water tableFresh

groundwater aquifer

Sea level

Saltwater

InterfaceSeaflo

or

Saltwater intrusion

Interface

Normal interface

EFFECTS OF OVERPUMPING AQUIFERS

Other Effects of Groundwater Other Effects of Groundwater OverpumpingOverpumping

Groundwater Groundwater overpumping can overpumping can cause: cause: land to sink land to sink

(subsidence(subsidence), ), “crushing” the aquifer “crushing” the aquifer

contaminated contaminated freshwater aquifers freshwater aquifers near coastal areas near coastal areas with saltwater.with saltwater.

Figure 14-11Figure 14-11

Other Effects of Groundwater Other Effects of Groundwater OverpumpingOverpumping

SinkholesSinkholes form when form when the roof of an the roof of an underground cavern underground cavern collapses after being collapses after being drained of drained of groundwater.groundwater.

Figure 14-10Figure 14-10

Groundwater Pumping in Saudi Groundwater Pumping in Saudi Arabia (1986 – 2004)Arabia (1986 – 2004)

Irrigation systems from the Irrigation systems from the nonrenewable nonrenewable aquiferaquifer appear as green dots. Brown dots are appear as green dots. Brown dots are wells that have gone dry.wells that have gone dry.

Figure 14-9Figure 14-9

20042004

19861986

Fig. 14-12, p. 316

Solutions

Groundwater Depletion

Prevention Control

Waste less water Raise price of water to discourage waste

Subsidize water conservation

Ban new wells in aquifers near surface waters

Tax water pumped from wells near surface waters

Buy and retire groundwater withdrawal rights in critical areas

Do not grow water-intensive crops in dry areas

Set and enforce minimum stream flow levels

USING DAMS AND RESERVOIRS USING DAMS AND RESERVOIRS TO SUPPLY MORE WATERTO SUPPLY MORE WATER

Large Large dams and reservoirsdams and reservoirs can can produce cheap electricityproduce cheap electricity reduce downstream floodingreduce downstream flooding provide year-round water for irrigating provide year-round water for irrigating

cropland…..cropland…..

But they also But they also displace peopledisplace people flood terrestrial ecosystemsflood terrestrial ecosystems disrupt aquatic systems.disrupt aquatic systems.

Fig. 14-13a, p. 317

Provides water for year-round irrigation of cropland

Flooded land destroys forests or cropland and displaces people

Large losses of water through evaporation

Provides water for drinking Downstream

cropland and estuaries are deprived of nutrient-rich silt

Reservoir is useful for recreation and fishing

Risk of failure and devastating downstream flooding

Can produce cheap electricity (hydropower)

Downstream flooding is reduced

Migration and spawning of some fish are disrupted

Fig. 14-13b, p. 317

Powerlines

Reservoir

Dam

PowerhouseIntake

Turbine

Case Study: The Colorado Basin – an Case Study: The Colorado Basin – an Overtapped ResourceOvertapped Resource

The The Colorado RiverColorado River has so many dams and has so many dams and withdrawals that it often does not reach the withdrawals that it often does not reach the ocean.ocean. 14 major dams and reservoirs, and canals.14 major dams and reservoirs, and canals.

Water is mostly used in Water is mostly used in desert areadesert area of the U.S. of the U.S.

Provides electricity from hydroelectric plants for Provides electricity from hydroelectric plants for 30 million people (1/1030 million people (1/10thth of the U.S. population). of the U.S. population).

Case Study: The Colorado Basin – an Case Study: The Colorado Basin – an Overtapped ResourceOvertapped Resource

Lake PowellLake Powell is is the second the second largest reservoir largest reservoir in the U.S.in the U.S.

It hosts one of It hosts one of the hydroelectric the hydroelectric plants located on plants located on the Colorado the Colorado River.River.

Figure 14-15Figure 14-15

Glen Canyon Dam

The Colorado River BasinThe Colorado River Basin

The area The area drained by this drained by this basin is equal to basin is equal to more than one-more than one-twelfth of the twelfth of the land area of the land area of the lower 48 states.lower 48 states.

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Fig. 14-14, p. 318

Dam

Aqueduct or canal

Upper Basin

LOWER BASIN

0 100 mi.

0 150 km

Lower BasinUPPER BASIN

IDAHO

WYOMING

Salt Lake City

Grand JunctionDenver

UTAH

NEVADACOLORADOLake

Powell

Las VegasGrand Canyon Glen Canyon

DamBoulder City

NEW MEXICO

ARIZONALos Angeles

Albuquerque

PhoenixSan Diego

MexicaliYuma

Tucson

All-American Canal Gulf of

CaliforniaMEXICO

CALIFORNIA

Palm Springs

Col

orad

o R

iver

Lake Mead

Hoover Dam

How Would You Vote?How Would You Vote?

Do the advantages of large dams outweigh Do the advantages of large dams outweigh their disadvantages?their disadvantages? a. No. Large dams inflict extensive environmental a. No. Large dams inflict extensive environmental

damage and humans must learn to meet their damage and humans must learn to meet their needs without them.needs without them.

b. Yes. Dams are critical in providing water and b. Yes. Dams are critical in providing water and electricity for people, especially in developing electricity for people, especially in developing countries. countries.

Case Study: Case Study: China’s Three Gorges DamChina’s Three Gorges Dam

on the Yangtze Riveron the Yangtze River

China’s Three Gorges DamChina’s Three Gorges Dam

Case Study: Case Study: China’s Three Gorges DamChina’s Three Gorges Dam

There is a debate over whether the There is a debate over whether the advantages of the world’s largest dam and advantages of the world’s largest dam and reservoir will outweigh its disadvantages.reservoir will outweigh its disadvantages. The dam is The dam is 2 kilometers long.2 kilometers long. The electric output is that of The electric output is that of 22 large coal-22 large coal-

burning or nuclear power plantsburning or nuclear power plants.. It It facilitates ship travelfacilitates ship travel reducing transportation reducing transportation

costs.costs. Dam has Dam has displaced 1.2 million people, and when displaced 1.2 million people, and when

filled will displace 5.4 million peoplefilled will displace 5.4 million people Dam is Dam is built over seismatic faultbuilt over seismatic fault and already has and already has

small cracks. small cracks.

Dam RemovalDam Removal Some dams are being Some dams are being removedremoved for for ecological ecological

reasonsreasons and because they have and because they have outlived their outlived their usefulnessusefulness (they tend to fill with silt in an average of (they tend to fill with silt in an average of about 50 years) about 50 years) In 1998 the In 1998 the U.S. Army Corps of EngineersU.S. Army Corps of Engineers announced announced

that it would no longer build large dams and diversion that it would no longer build large dams and diversion projects in the U.S.projects in the U.S.

The Federal Energy Regulatory Commission has The Federal Energy Regulatory Commission has approved the approved the removal of nearly 500 damsremoval of nearly 500 dams..

Removing dams can reestablish ecosystems, but can Removing dams can reestablish ecosystems, but can also also re-release toxinsre-release toxins from sediments into the from sediments into the environment.environment.

TRANSFERRING WATER FROM TRANSFERRING WATER FROM ONE PLACE TO ANOTHERONE PLACE TO ANOTHER

Transferring water can make unproductive Transferring water can make unproductive areas more productive but can cause areas more productive but can cause environmental harm.environmental harm. Pros:Pros: Promotes investment, jobs and strong Promotes investment, jobs and strong

economy.economy. Cons:Cons: It encourages unsustainable use of water It encourages unsustainable use of water

in areas water is not naturally supplied.in areas water is not naturally supplied.

Case Study: The California ExperienceCase Study: The California Experience

A massive A massive transfer of water transfer of water from water-rich from water-rich northern northern California to California to water-poor water-poor southern southern California is California is controversial.controversial.

Figure 14-16Figure 14-16

California AqueductCalifornia Aqueduct

Fig. 14-16, p. 321

CALIFORNIA

Sacramento River

North Bay Aqueduct

Lake Tahoe

San Francisco Sacramento

South Bay Aqueduct

Hoover Dam and Reservoir (Lake Mead)

NEVADA UTAH

Fresno

San Luis Dam and Reservoir Los Angeles

Aqueduct

Colorado River

California Aqueduct

Santa Barbara

Colorado River Aqueduct Central Arizona

Project

ARIZONA

Los Angeles

Salton Sea PhoenixSan Diego

Tucson

MEXICO

San Joaquin V

alley

Feather River

Shasta LakeOroville Dam and

Reservoir

Case Study: The Aral Sea DisasterCase Study: The Aral Sea Disaster

The The Aral SeaAral Sea was once the world’s fourth was once the world’s fourth largest freshwater lake.largest freshwater lake.

Figure 14-17Figure 14-17

Case Study: The Aral Sea DisasterCase Study: The Aral Sea Disaster

Case Study: The Aral Sea DisasterCase Study: The Aral Sea Disaster

Diverting water from the Aral Sea and its two Diverting water from the Aral Sea and its two feeder rivers feeder rivers mostly for irrigationmostly for irrigation has created has created a major ecological, economic, and health a major ecological, economic, and health disaster.disaster. About 85% of the wetlands have been About 85% of the wetlands have been

eliminated and roughly 50% of the local bird and eliminated and roughly 50% of the local bird and mammal species have disappeared.mammal species have disappeared.

Since 1961, the Since 1961, the sea’s salinity has tripledsea’s salinity has tripled and the and the water has dropped by 22 meterswater has dropped by 22 meters most likely most likely causing 20 of the 24 native fish species to go causing 20 of the 24 native fish species to go extinct.extinct.

Case Study: The Aral Sea DisasterCase Study: The Aral Sea Disaster

Case Study: The Aral Sea DisasterCase Study: The Aral Sea Disaster

DESALINIZATION OF SEAWATERDESALINIZATION OF SEAWATER Removing saltRemoving salt from seawater by current from seawater by current

methods is methods is expensive expensive and produces and produces large large amounts of salty wastewateramounts of salty wastewater that must be that must be disposed of safely.disposed of safely. DistillationDistillation: heating saltwater until it : heating saltwater until it

evaporates, leaves behind salt in solid evaporates, leaves behind salt in solid form. form.

Reverse osmosisReverse osmosis: uses high pressure to : uses high pressure to force saltwater through a membrane filter.force saltwater through a membrane filter.• Saudi Arabia- 70% of drinking waterSaudi Arabia- 70% of drinking water

SEEDING CLOUDS, AND TOWING SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIESICEBERGS AND GIANT BAGGIES

Seeding cloudsSeeding clouds with tiny particles of with tiny particles of chemicals to increase rainfall, chemicals to increase rainfall, towing towing icebergsicebergs or or huge bagshuge bags filled with freshwater filled with freshwater to dry coastal areas have all been proposed to dry coastal areas have all been proposed but are unlikely to provide significant but are unlikely to provide significant amounts of freshwater.amounts of freshwater. All three ideas are too expensiveAll three ideas are too expensive Seeding Clouds leaves chemical residuesSeeding Clouds leaves chemical residues

INCREASING WATER SUPPLIES BY INCREASING WATER SUPPLIES BY WASTING LESS WATERWASTING LESS WATER

We wasteWe waste about about two-thirdstwo-thirds of the water we of the water we use worldwide (50% in the US), but we could use worldwide (50% in the US), but we could cut this waste to 15%.cut this waste to 15%. 65-70% of the water people use throughout the 65-70% of the water people use throughout the

world is lost through evaporation, leaks, and world is lost through evaporation, leaks, and other losses.other losses.

Water is underpriced through Water is underpriced through government government subsidiessubsidies..

The lack of government subsidies for The lack of government subsidies for improving improving the efficiencythe efficiency of water use contributes to water of water use contributes to water waste.waste.

Fig. 14-18, p. 325

Center pivotCenter pivot

Drip irrigationDrip irrigation

Gravity flowGravity flow(efficiency 60% and

80% with surge valves)

Above- or below-ground pipes or tubes deliver water to individual plant roots.

Water usually comes from an aqueduct system or a nearby river.

(efficiency 90–95%)

(efficiency 80%–95%)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

INCREASING WATER SUPPLIES BY INCREASING WATER SUPPLIES BY WASTING LESS WATERWASTING LESS WATER

Sixty percentSixty percent of the world’s irrigation water is of the world’s irrigation water is currently wasted, but improved irrigation currently wasted, but improved irrigation techniques could techniques could cut this waste to 5-20%.cut this waste to 5-20%.

Center-pivot, low pressure sprinklersCenter-pivot, low pressure sprinklers sprays sprays water directly onto crop.water directly onto crop. It allows 80% of water to reach crop.It allows 80% of water to reach crop. Has reduced depletion of Ogallala aquifer in Has reduced depletion of Ogallala aquifer in

Texas High Plains by 30%.Texas High Plains by 30%.

Fig. 14-19, p. 326

Solutions

Reducing Irrigation Water Waste

• Line canals bringing water to irrigation ditches

• Level fields with lasers

• Irrigate at night to reduce evaporation

• Monitor soil moisture to add water only when necessary

• Polyculture

• Organic farming

• Don't grow water-thirsty crops in dry areas

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

• Irrigate with treated urban waste water

• Import water-intensive crops and meat

Solutions: Getting More Water for Solutions: Getting More Water for Irrigation in Developing Countries – Irrigation in Developing Countries –

The Low-Tech ApproachThe Low-Tech Approach

Many poor farmers in Many poor farmers in developing countries developing countries use low-tech methods use low-tech methods to pump groundwater to pump groundwater and make more and make more efficient use of rainfall.efficient use of rainfall.

Figure 14-20Figure 14-20

Fig. 14-21, p. 327

Solutions

Reducing Water Waste

• Redesign manufacturing processes

• Repair leaking underground pipes

• Landscape yards with plants that require little water: “Xeriscaping”

• Use drip irrigation

• Fix water leaks

• Use water meters

• Raise water prices

• 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 (“gray water”) to irrigate lawns and nonedible plants

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

• Don't waste energy

Raising the Price of Water:Raising the Price of Water: A Key to Water Conservation A Key to Water Conservation

We can reduce water use and waste by We can reduce water use and waste by raising the price of water while providing raising the price of water while providing low low lifelinelifeline rates for the poor. rates for the poor. When Boulder, Colorado introduced water When Boulder, Colorado introduced water

meters, water use per person dropped by 40%.meters, water use per person dropped by 40%. A 10% increase in water prices cuts domestic A 10% increase in water prices cuts domestic

water use by 3-7%.water use by 3-7%.

Solutions: Using Less Water to Remove Solutions: Using Less Water to Remove Industrial and Household WastesIndustrial and Household Wastes

We can mimic the way nature deals with We can mimic the way nature deals with wastes wastes instead ofinstead of using large amounts of using large amounts of high-quality water to high-quality water to wash away and dilute wash away and dilute industrial and animal wastes.industrial and animal wastes. Use Use nutrients in wastewaternutrients in wastewater before treatment as before treatment as

soil fertilizer.soil fertilizer. Use waterless and odorless Use waterless and odorless composting toiletscomposting toilets

that convert human fecal matter into a small that convert human fecal matter into a small amount of soil material.amount of soil material.

FLOODS: TOO MUCH WATERFLOODS: TOO MUCH WATER

Comparison of St. Louis, Missouri under Comparison of St. Louis, Missouri under normal conditions (1988) and after severe normal conditions (1988) and after severe flooding (1993).flooding (1993).

Figure 14-22Figure 14-22

TOO MUCH WATERTOO MUCH WATER Heavy rainfallHeavy rainfall, , rapid snowmeltrapid snowmelt, , removal of removal of

vegetationvegetation, and , and destruction of wetlands destruction of wetlands cause flooding.cause flooding.

Floodplains,Floodplains, which usually include highly which usually include highly productive wetlands, help provide natural productive wetlands, help provide natural flood and erosion control, maintain high water flood and erosion control, maintain high water quality, and recharge groundwater.quality, and recharge groundwater.

To minimize floods, rivers have been To minimize floods, rivers have been narrowed with levees and wallsnarrowed with levees and walls, and , and dammeddammed to store water. to store water.

Fig. 14-23a, p. 330

Oxygen released by vegetation

Diverse Diverse ecological ecological habitathabitat

Evapotranspiration

Trees reduce soil erosion from heavy rain and wind

Agricultural landSteady

river flow

Leaf litter improves soil fertility

Tree roots stabilize soil and aid water flow

Vegetation releases water slowly and reduces flooding

Forested Hillside

Fig. 14-23b, p. 330

Tree plantation

Roads Roads destabilize destabilize hillsideshillsides

Evapotranspiration decreases

Ranching accelerates soil erosion by water and wind

Winds remove fragile topsoil

Agricultural land is flooded and silted up

Gullies and Gullies and landslideslandslides

Heavy rain leaches nutrients from soil and erodes topsoil

Silt from erosion blocks rivers and reservoirs and causes flooding downstream

Rapid runoff causes flooding

After Deforestation

Human activitiesHuman activities have contributed to flood have contributed to flood deaths and damages.deaths and damages.

Figure 14-23Figure 14-23

These are not “Natural Disasters” !

Fig. 14-24, p. 331

Solutions

Reducing Flood Damage

Prevention Control

Preserve forests on watersheds

Strengthen and deepen streams (channelization)

Preserve and restore wetlands in floodplains

Tax all development on floodplains

Build levees or floodwalls along streams

Use floodplains primarily for -recharging aquifers -sustainable agriculture and forestry -recreation

Build dams

SOLUTIONS: USING SOLUTIONS: USING WATER MORE WATER MORE SUSTAINABLYSUSTAINABLY

We can use water more We can use water more sustainably by sustainably by cutting wastecutting waste raising water prices raising water prices preserving forests and preserving forests and

wetlands in water basinswetlands in water basins slowing population slowing population

growth.growth.

Figure 14-25Figure 14-25

Fig. 14-25, p. 333

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.

• Stop water leaks.

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

• Flush toilets only when necessary.

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

• Use recycled (gray) water for lawn, gardens, house plants, car washing.

• Eat less beef: 15,000 gallons of water per pound of beef produced.

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

• Xeriscape: Replace your lawn with native plants that need little if any watering and decorative gravel or rocks.

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

• Sweep or blow off driveways instead of hosing off with water.

• Use drip irrigation and mulch for gardens and flowerbeds.