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
