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Chapter 9:
Water Resources
Too much water: Flooding
• Flooding- both natural and human induced.
• Modern floods are highly destructive
because humans have:
− Removed water-absorbing plant cover
from soil.
− Constructed buildings on floodplains
• Floodplain- area bordering a river channel
that has the potential to flood
Urban vs. pre-Urban Floodplains
Floodplains
• Rather than rebuild levees adjacent to
rivers, experts suggest allowing some
flooding of floodplains during floods
Traditional levees
adjacent to river
Suggested levee style,
set back from river
Too Little Water
• Typically found in arid land
• Problems
• Drought
• Overdrawing water for irrigation purposes
• Aquifer depletion
• Subsidence
• Sinkholes
• Saltwater intrusion
NOTE: shown are center-pivot irrigation
circles…each one is the result of long pipes
that extend along the radius from the center
of the circle to the edge…rotating slowly to
spray the crops.
Subsidence
Subsidence- occurs when
large amounts of ground
water have been removed
from certain types of rocks.
Sinkhole
Sinkholes- Sinkholes are depressions or holes
in the land surface, they can be shallow or
deep, small or large, but all are a result of the
dissolving of the underlying limestone.
Agriculture, Industry and
Household Needs
• Agriculture- the largest
user of water around
the world
~70%
Agriculture, Industry and
Household Needs
• Irrigation techniques− Furrow irrigation- a trench that is flooded with
water.
− Flood irrigation- the entire field is flooded with
water.
− Spray irrigation- an apparatus that sprays water
across a field.
− Drip irrigation- using a slow dripping hose that is laid
on or buried beneath the soil.
− Hydroponic agriculture- crops grown in fertilized
water and no soil.
Agriculture, Industry and
Household Needs
• Industry- the second largest user of
water worldwide.
Agriculture, Industry and
Household Needs
• Households- the third largest user of
water worldwide .
Water Problems in US and Canada
• US has a plentiful
supply of
freshwater
• However, water is
NOT uniformly
distributed, so
many areas have
severe shortages
• Geographical
variations
• Seasonal variations
Water Problems in US and Canada
• Water shortages in West and Southwest
• Water is diverted and transported via aqueducts
Water Problems in US and Canada
• Mono Lake (Eastern CA)
• Rivers and streams that once fed this lake are
diverted to Los Angeles (275mi away)
• Becoming highly saline
• Court ordered water diversion reduction
• Colorado River Basin
• Provides water for 27-million people
• Numerous dams for Hydropower
• Colorado River no longer reaches ocean
• Delaware – a state without water
• Use of conservation-based pricing, in which
consumers are rewarded for conserving water is
helping water managers meet needs
Colorado River bed in Mexico
Water Problems in US and Canada
Groundwater (Aquifer) Depletion
Water Conservation
Reducing Agricultural Water Waste
• Agriculture is very inefficient with water
• Microirrigation- irrigation that conserves
waster by piping to crops through sealed
systems
• Also called drip or trickle irrigation
Water Conservation
Reducing Industrial Water Waste
• Stricter laws provide incentive to conserve
water
• 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!
Global Water Problems
• Amount of freshwater on planet CAN meet
human needs
− BUT, it is unevenly distributed and some
places lack stable runoff
• Problems:
−
−
−
−
Climate Change
Drinking Water
Population Growth
Sharing Water Resources Among Countries
Global Water Problems
• Water and Climate Change
− Climate change affects the type and
distribution of precipitation
− Potential issues:
− Reduced snowfall will impact water
resources downstream
− Sea level rise will cause saltwater intrusion
into drinking water supplies
Sharing Water Resources
• Rhine River Basin
− Countries upstream discharged pollutants into river
− Countries downstream had to pay to clean the water
before they could drink it
• Aral Sea
− Water diversion for irrigation has caused sea to
become too saline
1967
1997
The Future of Water Availability
• Water ownership- people can have rights to
water use, but they do not own the water.
• Water conservation- using techniques such as
more efficient water fixtures, faucets and
washing machines.
Working toward Sustainability
• Gray water- wastewater from baths, showers,
bathroom sinks and washing machines.
− While not suitable for drinking, gray water is perfectly
suitable for watering lawns and plants, washing cars,
and flushing toilets
Conserving water at Home
• Install water-saving shower heads and faucets
• Install low-flush toilets
• Fix leaky fixtures
• Purchase high efficiency appliances
• Modify personal habits
• Use the dishwasher instead of washing by
hand