WaterWater

Water: A Vital ResourceWater: A Vital Resource

Oceans Oceans and and

saline saline lakeslakes

97.4%97.4%

Fresh Fresh WateWater r 2.6%2.6%

Supply of Water ResourcesSupply of Water Resources

FreshwaterFreshwater Readily accessible freshwaterReadily accessible freshwater

Biota0.0001%

Biota0.0001%

Rivers0.0001%Rivers

0.0001%

Atmosphericwater vapor

0.001%

Atmosphericwater vapor

0.001%

Lakes0.007%

Soilmoisture0.005%

Groundwater0.592%

Groundwater0.592%

Ice capsand glaciers

0.1.984%

0.014%0.014%

Surface WaterSurface Water

• Surface runoffSurface runoff– Water flowing off the land into Water flowing off the land into

bodies of waterbodies of water– Represents a stable source of Represents a stable source of

waterwater• Watershed (Drainage Basin)Watershed (Drainage Basin)

– Area of land drained by a single Area of land drained by a single river or streamriver or stream

GroundwaterGroundwater

Evaporation and transpirationEvaporation and transpiration

EvaporationEvaporation

StreamStream

InfiltrationInfiltration

Water tableWater tableInfiltrationInfiltration

Unconfined aquiferUnconfined aquifer

Confined aquiferConfined aquifer

LakeLake

Well requiring a pumpWell requiring a pump

FlowingFlowingartesian wellartesian well

RunoffRunoff

PrecipitationPrecipitation

ConfinedConfinedRecharge AreaRecharge Area

AquiferAquifer

Less permeable materialLess permeable materialsuch as claysuch as clay

Confirming permeable rock layerConfirming permeable rock layer

Ground WaterGround Water

Unconfined Aquifer Recharge AreaUnconfined Aquifer Recharge Area

Use of Water ResourcesUse of Water Resources

• AgricultureAgriculture• IndustryIndustry• DomesticDomestic• Power Power

PlantsPlants

Humans use about 50% of reliable runoff Humans use about 50% of reliable runoff

United StatesUnited States

Industry 11%Industry 11%

Public 10%Public 10%

PowerPowercoolingcooling

38%38%

AgricultureAgriculture41%41%

5,500

5,000

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

500

1900 1920 1940 1960 1980 2000

Wat

er u

se (

cub

ic k

ilom

eter

s p

er y

ear) Total use

Agricultural use

Industrial use

Domestic use

Year

Water in the United States

Water in the United States• Average Average

precipitation precipitation (top)(top) in relation in relation to water-deficit to water-deficit regions andregions and

• their proximity their proximity to metropolitan to metropolitan areas areas (bottom).(bottom).

Too Little WaterToo Little Water

1)1) Dry climateDry climate• Air circulation Air circulation

patternspatterns

2)2) DroughtDrought• 21 days+21 days+• Precipitation <70%Precipitation <70%• Increased Increased

evaporationevaporation

3)3) DesiccationDesiccation• Drying of the soilDrying of the soil

4)4) Water stressWater stress• Low per capita Low per capita

availabilityavailability• Caused by Caused by

increased increased populationpopulation

• Limited runoff levelsLimited runoff levels

Acute shortage

Adequate supply

ShortageMetropolitan regions with population greater than 1 million

Water stressedWater stressed – – reliable runoff per reliable runoff per person below 1700 person below 1700 cu meters per yearcu meters per year

Water scarcityWater scarcity – per – per capita availability capita availability below 1000 cu below 1000 cu meter per yearmeter per year

500 million people live in 500 million people live in countries that are either countries that are either water stressed or water water stressed or water

scarcescarce• limited access (live far away)limited access (live far away)• arrives during short periodsarrives during short periods• hydrological povertyhydrological poverty

–Collect water from unsafe Collect water from unsafe sourcessources–Purchase from private vendorPurchase from private vendor

Increasing Fresh Water SuppliesIncreasing Fresh Water Supplies

1.1. Build dams and reservoirs to Build dams and reservoirs to store runoffstore runoff

2.2. Bring surface water from another Bring surface water from another areaarea

3.3. Withdraw groundwater.Withdraw groundwater.4.4. Convert salt water to fresh waterConvert salt water to fresh water5.5. Waste less waterWaste less water6.6. Import food to reduce water useImport food to reduce water use

Using Dams and Reservoirs to Supply More

Water

(To Dam or Not To Dam)

Using Dams and Reservoirs to Supply More

Water

(To Dam or Not To Dam)

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

• • Deliver nutrients to the sea which Deliver nutrients to the sea which helps to sustain coastal fisherieshelps to sustain coastal fisheries

• • Deposit silt that maintains deltasDeposit silt that maintains deltas

• • Purify waterPurify water

• • Renew and nourish wetlandsRenew and nourish wetlands

• • Provide habitats for aquatic lifeProvide habitats for aquatic life

• • Conserve species diversityConserve species diversity

Ecological Services of RiversEcological Services of Rivers

Transferring Water from One Place to AnotherTransferring Water from One Place to Another

North BayAqueductNorth BayAqueduct

South BayAqueductSouth BayAqueduct

California AqueductCalifornia Aqueduct

CALIFORNIANEVADA UTAH

MEXICO

Central ArizonaCentral ArizonaProjectProject

Colorado RiverAqueduct

Los AngelesAqueduct

Shasta Lake

Sacramento

Fresno

Phoenix

Tucson

ARIZONA

ColoradoRiver

SacramentoRiverSacramentoRiver

San FranciscoSan Francisco

Los AngelesLos Angeles

San DiegoSan Diego

Watershed transferWatershed transfer

California California Water ProjectWater Project

Increasing Fresh Water SuppliesIncreasing Fresh Water Supplies

1.1. Build dams and reservoirs to Build dams and reservoirs to store runoffstore runoff

2.2. Bring surface water from another Bring surface water from another areaarea

3.3. Withdraw groundwater.Withdraw groundwater.

Tapping GroundwaterTapping Groundwater

•AdvantagesAdvantages– Year-round useYear-round use– No evaporation lossesNo evaporation losses– Often less expensiveOften less expensive

•Potential Problems!Potential Problems!– ManyMany

Problems with Using GroundwaterProblems with Using Groundwater

1)1)Water Table LoweringWater Table Lowering

Initial water table

Cone ofdepression

Originalwater table

Loweredwater table

Problems with Using Groundwater

Problems with Using Groundwater

2)2) Aquifer depletionAquifer depletion• Ogalala AquiferOgalala Aquifer

WYOMING SOUTH DAKOTA

NEBRASKA

COLORADO

KANSAS

OKLAHOMA

NEW MEXICO

TEXAS

0 100Miles

Kilometers

Less than 61 meters (200 ft)

61-183 meters (200-600 ft)

More than 183 meters (600 ft)(as much as 370 meters or 1,200 ft.in places)

0 160

Other Effects of Groundwater OverpumpingOther Effects of Groundwater Overpumping

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

Problems with Using GroundwaterProblems with Using Groundwater4)4) Saltwater intrusion: when groundwater is Saltwater intrusion: when groundwater is

depleted faster than it rechargesdepleted faster than it rechargesMajor irrigation

wellWell contaminated

with saltwater

SaltwaterIntrusion

NormalInterface

Freshgroundwater

aquifer

Interface Interface

Saltwater

Sea LevelWater table

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

Problems with Using GroundwaterProblems with Using Groundwater

5)5)Chemical contaminationChemical contamination

6)6)Reduced stream flowReduced stream flow

• Tragedy of the commonsTragedy of the commons

Converting Salt Water to Fresh WaterConverting Salt Water to Fresh Water

• DesalinationDesalination – removing dissolved – removing dissolved salts from ocean water or brackish salts from ocean water or brackish water.water.

– Distillation desalinationDistillation desalination•Heating salt water until it Heating salt water until it evaporates.evaporates.

– Reverse osmosis desalinationReverse osmosis desalination•Salt water is pumped at high Salt water is pumped at high pressure through a thin membranepressure through a thin membrane

Converting Salt Water to Fresh WaterConverting Salt Water to Fresh Water

– Desalination is Desalination is very expensivevery expensive• Larger amounts of Larger amounts of energy neededenergy needed

– Desalination produces Desalination produces large large quantities of wastewaterquantities of wastewater • waste disposal problemwaste disposal problem

Making it RainMaking it Rain

• Cloud SeedingCloud Seeding– Water condensation nucleiWater condensation nuclei– Silver iodide particlesSilver iodide particles

• Limited SuccessLimited Success– Not useful in dry areasNot useful in dry areas– Potential pollution from cloud Potential pollution from cloud

seeding chemicalsseeding chemicals– Legal disputes: ownership of Legal disputes: ownership of

cloudsclouds

Using Water More EfficientlyUsing Water More Efficiently

• Reduce losses due to leakageReduce losses due to leakage– 60 to75% of water people use is 60 to75% of water people use is

lost!lost!

• Causes of wasteCauses of waste– Water subsidy policyWater subsidy policy

• Artificially low cost of waterArtificially low cost of water• False sense of abundanceFalse sense of abundance

Using Water More EfficientlyUsing Water More Efficiently

• Causes of waste cont.Causes of waste cont.– Water lawsWater laws

• Doctrine of riparian rightsDoctrine of riparian rights (East) (East)– Anyone owning land adjoining stream Anyone owning land adjoining stream

has right to water has right to water

• Principle of prior appropriationPrinciple of prior appropriation (West)(West)

– First-come, first-servedFirst-come, first-served

• Common lawCommon law governs governs groundwatergroundwater– Subsurface water belongs to whoever Subsurface water belongs to whoever

owns the land above itowns the land above it

– Fragmented watershed Fragmented watershed managementmanagement

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.

Too Much Water: FloodsToo Much Water: Floods

Natural phenomena• heavy rain, melting snow

Natural phenomena• heavy rain, melting snow

Floodplain

Levee Floodwall

Dam

Reservoir

Renew and replenishRenew and replenish

Aggravated by human activities

Aggravated by human activities

Solutions: Achieving a More Sustainable Water FutureSolutions: Achieving a More Sustainable Water Future

Efficient irrigationEfficient irrigation

Water-saving technologiesWater-saving technologies

Improving water managementImproving water management

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.

• 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 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.