Water

Chapter 14

Essential Question #1

Why is water so important, how much fresh water is available to us, and how much of it are we using?

Why is Water Important

• Major part of organisms (60%)– Without water, chemical

reactions can’t occur

• Affects Climate

• Carves the Land

• Removes and dilutes wastes & pollutants

• Cycles continuously

Where is Freshwater Available?

• 97.4% salt water, 2.6% freshwater

• Of that 2.6% freshwater:– 75% is frozen– 90% of melted

freshwater is in lakes, soil & air

Fig. 11-2, p. 238

All water Fresh water Readily accessible fresh water

Oceans andsaline lakes97.4%

Fresh water2.6%

Groundwater0.592%

Ice capsand glaciers1.984%

Soilmoisture0.005%

Biota0.0001%

Rivers0.0001%

Atmosphericwater vapor0.001%

0.014%

Lakes 0.007%

Earth’s Water Budget

Only about 0.024% of water is available as accessible, liquid freshwater!

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%

GlobalAvailability of

Water Resources

Ground Water

• Water below the earth’s surface, stored in spaces in soil, gravel, sand & rock

– Water table – top of ground water layer (zone of saturation)

• Rises & falls w/ precipitation changes

– Aquifers – deep layers of porous rock holding water• 1/3 of world pumps water from aquifers

Evaporation and transpiration Evaporation

Stream

Infiltration

Watertable

Infiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRechargeArea

Recharge Unconfined Aquifer

Lesspermeable materialsuch as clay Confining impermeable rock layer

Unconfined Aquifer Recharge Area

Fig. 11-3, p. 239

Groundwater Systems

Accessing Aquifers

Aquifers

• Renewable Aquifers

– Natural Recharge – precipitation percolates down to refill (slow process)

– Lateral Recharge – refilled from side by streams/rivers

• Nonrenewable Aquifers– Receive little to no recharge

Surface Water• Surface Runoff

– Precipitation that doesn’t evaporate or soak into ground

– 2/3 lost to seasonal flooding

• Watershed / Drainage Basin– The region where runoff flows into

water bodies

• Reliable Runoff– The amount of runoff we can count

on as a stable source of fresh water *(1/3 of surface runoff)

Water Withdrawal• Consumptive Use

– Does not return water to original source– ~70% of withdrawn water

• Nonconsumptive Use– Temporarily removes water from source– Ex: Power plant using water for cooling

How much water do we use?

• 70% = Irrigation

• 20% = Industrial Use

• 10% = Cities & Residencies

(1lb of beef = 6 months of showers!)

How much water do we use?

• We currently withdraw 34% of reliable runoff.

• But to meet demands of growing population we may be using 70-90% by 2025.

Fig. 11-4a, p. 240

Annual Precipitation

determines who has & does not

have water resources

Freshwater Resources in the United States

17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.

Figure 14-5Figure 14-5

Cooperation?• No cooperative

agreements exist for 158 of 263 watersheds shared by two or more countries

• Conflicts likely to increase as population & demand continue to rise

Question #2

What causes freshwater shortages, and what

can be done to increase freshwater supplies?

Causes of Freshwater Shortages

• Dry Climate

• Drought

• Large Population

• Poverty

Stress on the World’s River Basins1 in 6 don’t have access to adequate & affordable supply of

clean water.

Buy 2050 this could be 1 in 4.

Hydrological Poverty

• Could you live on 1 gallon of water/day for all your needs?

Ways to Increase Freshwater Supplies

• Dams & Reservoirs

• Water Transfers

• Using Groundwater

Ways to Increase Freshwater Supplies

• Desalination– Distillation &

reverse osmosis

• Import food

• Waste Less

Essential Question #3

What are the advantages and

disadvantages of withdrawing

groundwater?

Withdrawing Groundwater To Increase Supplies

Aquifers are Renewable as long as NOT:OverpumpedContaminated

Groundwater depletion for Irrigation is a growing problem

At least one-fourth of the farms in India are being irrigated from overpumped aquifers.

Effects of Groundwater Overpumping

Contaminates freshwater aquifers near coastal areas with saltwater.

Sinkholes form when drained aquifers collapse

Groundwater Contamination• Example: Contamination from fracking

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: A Growing Problem

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

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

Figure 14-8Figure 14-8

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 watersBuy and retire

groundwater withdrawal rights in critical areas

Do not grow water-intensive crops in dry areas

Set and enforce minimum stream flow levels

Essential Question #4

What are the advantages and disadvantages of using dams to supply

more water?

Beaver’s are Fans

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

River

The Colorado Basin – an Overtapped Resource

The Colorado River has so many dams and withdrawals that it often does not reach the ocean.

14 major dams and reservoirs, and canals.

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

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

The Colorado River Basin

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

Figure 14-14Figure 14-14

Dam Removal

• Since 1998, U.S. Army Corps of Engineers no longer building dams / water diversion projects in US

• Many dams being removed b/c of age or ecological reasons– Difficult & Expensive

Essential Question #5

What are the advantages and disadvantages of

transferring large amounts of water from one place to another?

Advantages of Water Transfer

• Makes unproductive areas more productive

• Promotes investment / jobs / economy

Disadvantages of Water Transfer

• Encourages unsustainable use in water scarce areas

• Reduces water availability from source

• Examples: – Aral Sea Disaster

– California Water Project

– South-to-North China Water Diversion Project ($58 billion)

Essential Question #6

How can removing salt from water solve our

water supply problems? Why or why

not?

Desalination

Disadvantages

• Not Practical

– High cost / High Energy

– Disposal of waste salts / minerals / toxins

Other Ideas: Unlikely

• Cloud Seeding

• Towing Icebergs

• Giant Water Bags

Essential Question #7

How can we waste less water?

Water Waste

• 65-70% of water used is lost to evaporation, leaks, & other losses

• About 60% of water used for crop irrigation is lost due to inefficient methods

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.

Improving Irrigation

Reducing Water Waste• Charge more to increase

conservation

• Improve irrigation techniques (drip irrigation)

• Give financial incentives (subsidies) for improving water conservation in agriculture / industry

Reducing Water Waste

• Fix leaks in homes, businesses, infrastructure

• Install low-flow toilets, showers, etc

• Used recycled water (gray water) for watering home

• Plant drought tolerant plants

Rain Water Recycling Systems

Fig. 14-21, p. 327

Solutions

Reducing Water Waste

• Redesign manufacturing processes

• Repair leaking underground pipes

• Landscape yards with plants that require little water

• 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 to irrigate lawns and nonedible plants

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

• Don't waste energy

Essential Question #8

What causes flooding, and what can we do to

reduce flood risks?

What is a flood?

• When water leaves its normal channel and spills into its adjacent floodplain

What causes flooding?

• Heavy Rain

• Rapid Snow Melt

• Removing Plants

• Destroying Wetlands

• Impervious Structures– Pavement / Buildings

Fig. 11-23, p. 253

Flooding After Deforestation of a Hillside

How can we reduce flood risks?

• Straighten & deepen rivers/streams

• Build Levees

• Build Dams

– These solutions have ecological problems• Can increase erosion• Can be overwhelmed by excess flood water

How can we reduce flood risks?

• Preserve & Restore Wetlands (best solution)– Act as a natural sponge for flood waters

• Better identify flood plains & think about where we live

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, and recreation

Build dams

Essential Question #9

How can we use the earth’s water more

sustainably ?

Sustainable Water Use• Improve monitoring of water sources to improve

management

• Protect ecosystems involved in water cycle

• Regulate withdrawals

• Change subsidies to promote water conservation

• Improve wastewater treatment

• Slow population growth & thus demand

Fig. 11-21, p. 251

• 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.

What Can You Do?Water Use and Waste

What Can We Do?

The Awesome Water Bottle

• http://www.youtube.com/watch?v=pzdBCxZhKpQ