Ch. 13: Water Resources

CH. 13: WATER RESOURCESBY CHRIS MCCORD AND

WESTON TAKATA

How Can We Deal With Our Water Problems?

Will We Have Enough Usable Water?

We Are Misusing Our FreshwaterEarth’s surface is 71% saltwaterWater is necessary for life, food, and shelterGlobal Health Issue – lack of water is single

largest cause of illnessEconomic Issue – vital for reducing poverty

and producing food and energyEnvironmental Issue – many environmental

indicators related to water are worsening

Availability of FreshwaterOnly .024% of Earth’s water is readily availableHydrologic cycle recycles Earth’s freshwaterGroundwater – collected water undergroundAquifers – underground caverns of rock through

which water flowsSurface water – lakes, rivers, streams, etc.Reliable surface runoff – the amount of surface

runoff that we can generally count on as a source of freshwater

We are using a large and growing portion of the world’s reliable surface runoff

Water Cycle

Water ShortageDrought – prolonged period in which

precipitation is at least 70% lower and evaporation is higher than normal

Water shortages are growingBy 2025, 3 billion people could lack access to

safe water30% of Earth’s land experiences severe

droughtWho should own and manage freshwater

resources?

Is Extracting Groundwater the Answer?

Withdrawing GroundwaterAdvantages DisadvantagesUseful for drinking and

irrigationAvailable year-roundExists almost

everywhereRenewable if not

overpumped or contaminated

No evaporation lossesCheaper

Aquifer DepletionSinking of land –

subsidencePolluted aquifersSaltwater intrusion near

coastReduced water flows

into surface watersIncreased cost and

contamination

Aquifer Depletion

Is Building More Dams the Answer?

Large Dams and ReservoirsDam – structure built across a river to control

the river’s water flowReservoir – created behind damIncrease reliable runoffGenerate electricityAreas must be flooded to build the damReservoirs can lose water due to evaporation

Dams

Will Transferring Water Solve Our Problems?

California Water ProjectDivert water from

North to arid SouthMajor issue in CAAnalysts improve

irrigation efficiency

Case Study: The Shrinking of the Aral Sea1960 Soviet Union

creates large irrigation system

Salt desert left behind

Himalayas meltingLocals becoming illHope for future

China’s Water Transfer ProjectWater arid NorthBenefits outweigh

risks & costsUnfortunate ending

for China?

What about Converting Saltwater to Freshwater?

Desalination

Distillation

•Evaporate water & condense it•Requires lot of energy

Reverse Osmosis (Microfiltration)

•Pressure pushes water through filter•Expensive

How Can We Use Water Sustainably?

IrrigationThree types of Irrigation:

Gravity Flow 60% efficiency; 80% w/ surge valve

Center Pivot 80% efficiency; 90-95% w/ LEPA sprinkler

Drip Irrigation 90-95% efficiency

Flood Irrigation

Center Pivot Irrigation

Drip Irrigation

Domestic Water Use

Solutions for Sustainable Water Use at Home and in Industry

FloodplainsFlat land

surrounding streams/rivers with potential for flooding

Humans have major impact on frequency & damage of flooding

We can reverse the current trend

Case Study: Flooding in BangladeshMany people on small amount of landFlat terrain at sea levelAnnual monsoon flooding; 1 major every 50 yrs.Due to human hand, major flood every 4 yrs.Global warming a problem for future

In Depth Look – Hoover Dam

Hoover DamBorder of Arizona and

Nevada – Colorado RiverOpened in 1936726 feet highReservoir – Lake Mead –

167,800 sq milesGenerates 4.2 billion

KWh annuallyProvides power to

Nevada, Arizona, and Southern California

Environmental ImpactDecline of estuary at Colorado River DeltaEliminated natural flooding of Colorado River

– causing extinctionsDecreasing water levels due to evaporation