Chapter 13Water: A Limited Resource

Overview of Chapter 13Importance of Water

Hydrologic CycleWater Use and Resource Problems

Too Much WaterToo Little Water

Water Problems in US and CanadaGlobal Water Problems

Sharing Water ResourcesWater Management

Providing Sustainable Water SupplyWater Conservation

Importance of WaterCookingWashingUse large amounts

for:AgricultureManufacturingMiningEnergy productionWaste disposal

Use of freshwater is increasing

Properties of WaterComposed of 2 Hydrogen and 1

oxygenExists as solid, liquid or gasHigh heat capacity – absorbs a lot

of solar energy without increasing in temperature much.

Earth’s temperature matches temperature for water as a liquid.

“universal solvent” allows dissolved gases and minerals in water, including pollutants

Colder water is more dense until 4 Celsius, then becomes less dense (ice floats and allows living things beneath)

Hydrologic Cycle

Distribution of Water

Only 2.5% of water on earth is freshwater

2% is ice!Only ~0.5% of

water on earth is available freshwater

Check for understanding4 - I can explain to my peers at least 5

properties of water and how water is distributed on earth.

3 - I understand 3-4 properties of water and how water is distributed on earth.

2 - I can explain at least 2 properties of water and how water is distributed on earth.

1 - huh? I know 1 property of water.

Freshwater TerminologySurface water

Precipitation that remains on the surface and does not seep into soil

RunoffMovement of surface water to lakes, rivers, etc.

Watershed (drainage basin)Land area that delivers water into a stream or

river systemGroundwater

Freshwater under the earth’s surface stored in aquifers

AquiferUnderground caverns and porous layers of sand,

gravel and rock in which groundwater is storedUnconfined and confined (artesian)Water table

Freshwater Aquifer

Check for understanding4 - I can explain to my peers the difference between

a confined and unconfined aquifer, what a water table is and the difference between groundwater, surface water, runoff, and a watershed is.

3 - I understand the difference between a confined and unconfined aquifer, but might not fully understand the difference in one of the following terms: a water table, groundwater, surface water, runoff, and watershed

2 - I am confused about at least 2 of the above terms

1 - I am confused about at least 3 of the above terms

Water Use and Resource ProblemsFall into Three Categories

Too much waterToo little waterPoor quality/contamination (discussed later)

Water UseMostly for irrigation for agriculture: 68%

Even arid (deserts) & semiarid land grow crops with enough H2O

Asia uses mostIndustryDomestic/municipal: 8.6%

xeriscaping

Too Much WaterFlooding

Both natural and human-induced. Causes???Modern floods are highly destructive because

humans:Remove water-absorbing plant cover from soilConstruct buildings on floodplains

FloodplainArea bordering a river channel that has the

potential to floodNaturally leave behind organic matter in soil – good.

Flood consequences???

Urban vs. Pre-Urban Floodplains

FloodplainGovernment restrictions on building

Levees can fail

o Rather than rebuild levees adjacent to rivers, experts suggest allowing some flooding of floodplains during floodso Less damage if

floodedo Replenish soilo Save money

Left: Left: Traditional Traditional levees levees adjacent to adjacent to riverriver

Right: Right: Suggested Suggested levee style, set levee style, set back from back from riverriver

NEW ORLEANS: HURRICANE KATRINA: AUGUST 2005

Case-In-Point Floods of 1993: Mississippi River

Worsened due to:1.Draining wetlands for farms and homes

2. Building levees (can force more surge upstream)

3. Building on floodplains

Similar to New Orleans

Check for understanding4 - I can explain to my peers the causes and

consequences of flooding and the problems associated with flooding and why modern societies suffer more damage from them.

3 - I understand the causes and consequences of flooding and the problems associated with flooding and why modern societies suffer more damage from them

2 - I need to reread my notes, but I understand

1 - I don’t fully understand flooding.

Too Little WaterTypically found in arid land (40% of population

– Africa/Asia)Women may walk to get water instead of school

ProblemsDroughtRemove native water absorbing plants and

replace with crops/livestock overgraze more runoff, less water in soil

Overdrawing water for irrigation purposes saltier estuaries, dried

wetlands (loss of bird breeding grounds)

Too Little WaterProblems (continued)

Aquifer depletionSubsidence – sinking of land on porous rock Sinkholes – eroded limestoneSaltwater Intrusion (coasts)

Saltwater Intrusion (coasts)

Problems (continued)Aquifer depletion

Water Problems In US

US has a plentiful supply of freshwater

Many areas have a severe shortagesGeographical

variationsSeasonal

variations

Water Problems in USWater shortages in West and Southwest

Historically for irrigation, now more water for industrial and municipals due to increased population

Water is diverted and transported via aqueducts

Water Problems in US Surface Water

Mono Lake (Eastern CA)Rivers and streams that once fed this lake are

diverted to Los Angeles (275mi away)Becoming highly saline due to water diversion

disrupt food chainCourt ordered water diversion reductionLA efforts to use more reclaimed water

Colorado River BasinProvides water for 27-million people –

Colorado, California, Arizona, into MexicoNumerous dams for Hydropower; also create

resevoirsColorado River no longer reaches ocean

HOOVER DAM: BETWEEN ARIZONA AND NEVADA

SALMON FISH LADDER

Colorado River bed in Mexico

Check for understanding4 - I can explain to my peers how water

diversion and dams can disrupt the amount of water in effected areas.

3 - I understand how water diversion and dams can disrupt the amount of water in effected areas

2 - I need to reread my notes, but I understand

1 - I don’t fully understand the impact of water diversion projects and dams.

Water Problems in US and -GroundwaterAquifer Depletion – especially Arizona,

California, High Plains

Case study: Ogallala AquiferHigh PlainsLargest groundwater in

worldUses 30% of irrigation

water in US – corn, wheat, soybean, livestock (6% of land)

Water table down 100 ft in some areas (rate of recharge less than rate of extraction) cost money to deepen wells, lose $ on dead crops

Global Water ProblemsAmount of freshwater on planet CAN meet

human needsBUT, it is unevenly distributed and some

places lack stable runoff

Global Water Problems

1. Water and Climate ChangeClimate change affects the type and distribution

of precipitationPotential issues:

Reduced snowfall will impact water resources downstream

Sea level rise will cause saltwater intrusion into drinking water supplies

Global Water Problems2. Drinking Water Problems

Many developing countries have insufficient water to meet drinking and household needs (1.1 billion lack safe water, 2.6 billion no good disposal of wastewater/fecal waste) illness Ex: CholeraEx: Sahel region of AfricaHelp: World Bank, US

Agency for International Development (AID)

3. Population GrowthIncrease in population means an increase in

freshwater requirementsLimits drinking water availableLimits water available for agriculture (food)Ex: Northern China – Yellow River, Indus

River in Pakistan, Mexico (aquifer)

Global Water Problems

4. Sharing Water Resources Among CountriesRhine River Basin (right)

Countries upstream discharged pollutants into river

Countries downstream had to pay to clean the water before they could drink it

Aral SeaKazakhstan and surrounding

countriesWater diversion for irrigation

has caused sea to become too saline decreased biodiversity

Aral Sea

19671967 19971997

Check for understanding4 - I can explain to my peers how climate

change, pathogens, a growing population, and water diversion can reduce water availability.

3 - I understand how climate change, pathogens, a growing population, and water diversion can reduce water availability

2 - I need to reread my notes, but I understand

1 - I don’t fully understand the impact of climate change, pathogens, a growing population, and water diversion can have on water availability.

Global Water Problems5. Potentially Volatile

International Water SituationsJordan River – supplies

many middle Eastern countries

Nile River (NE Africa) – Sudan and Ethiopia using more (increased population) and affecting Egypt’s supply

Water Management

FUN FACT: For every kilogram of animal protein produced, livestock are fed nearly 6 kg of plant protein. Every kilogram of beef produced takes 100,000 liters of water. A kilogram of wheat requires 900 liters of water.

Water ManagementMain Goal: Provide sustainable supply of

high-quality waterRequires humans to use resource carefullyDams and ReservoirsWater Diversion ProjectsDesalinization

THREE GORGES DAM - CHINA

Dams and ReservoirsBenefits:

Ensure year-round supply of water with regulated flow

Generate electricityProvide recreational

activitiesDisadvantages

Alter the ecosystem Reduce sediment load

downstreamDisplace humansDisrupt salmon migration for

breeding

Dams and ReservoirsGlen Canyon Dam

Regulated flow has changed ecosystemTo rectify situation

Canyon has been flooded several timesSmall floods compared to natural floodsStill helps rebuild habitat

Water Diversion ProjectsDiverting water via

aquaducts/canalsEx: Mono Lake, Aral

SeaControversial and

expensive

ARAL SEA: Kazakhstan-Uzbekistan border

DesalinizationRemoval of salt from ocean or brackish

waterTwo methods:

Distillation- salt water is evaporated, and water vapor is condensed into freshwater (salt left behind)

Reverse Osmosis- involves forcing salt water through a membrane permeable to water, but not salt

Very expensive due to large energy inputWhat to do with left over salt?

Check for understanding4 - I can explain to my peers how

dams/reservoirs, desalinization, and water diversion makes water available for human use and the consequences of each.

3 - I understand how dams/reservoirs, desalinization, and water diversion makes water available for human use and the consequences of each

2 - I need to reread my notes, but I understand 1 - I don’t fully understand how dams/reservoirs,

desalinization, and water diversion makes water available for human use and the consequences of each

Water ConservationReducing Agricultural Water Waste

Drip Irrigation- irrigation that conserves water by piping to

crops through sealed systemsAlso called microirrigation or trickle irrigation

Water ConservationReducing Industrial Water Waste

EX: paper, petroleum, food processing

Stricter laws (and enforcement of those laws) provide incentive to conserve waterEX: Recycling water within the plant

Water scarcity (in addition to stricter pollution control requirements) will encourage further industrial recycling

Potential to conserve water is huge!

Water Conservation

Reducing Municipal Water Waste : reduce, reuse, recycle

Gray Water (reclaimed water)Can be used to flush

toilets, wash car or water lawn

Water saving household fixtures

Raising costs to reflect real cost

Government incentives

Conserving at HomeInstall water-saving

shower heads and faucetsInstall low-flush toiletsFix leaky fixturesPurchase high efficiency

appliances – dishwasher/washing machine

Modify personal habitsShorter showers, showers

not bathsUse the dishwasher

instead of washing by hand

Check for understanding4 - I can explain to my peers ways for

agriculture, industry, and homes can conserve water.

3 - I understand ways for agriculture, industry, and homes can conserve water

2 - I need to reread my notes, but I understand

1 - I don’t fully understand ways for agriculture, industry, and homes can conserve water.