Importance of Water
• Covers 71% of Earth’s surface
– 97% by volume is found in the ocean
– 3% is fresh water (2.997% in glaciers and ice
– 0.024% freshwater easily accessible in
groundwater, lakes, streams, etc.
• Water is constantly recycled via the hydrologic
• Canada has 0.5% of the world
population but has 20% of available
• China has 20% of the world population
but only 7% of available freshwater
• Asia has 60% of the world population
but 30% of the available freshwater
Important Properties of Water
• Hydrogen Bonds – creates the adhesive and
cohesive forces of water
– Causes water to exist as a liquid over a wide
• Water has a high heat capacity
– Protects organisms from heat fluctuations
– Moderates Earth’s climate
– Good coolant for engines, power plants, etc.
• Dissolves a variety of compounds (polarity)
– “universal solvent”
• Ionizes which maintains pH (H+, OH-)
• Filters out UV light
• Expands by 10% when frozen, so it floats
• Groundwater –
through geologic features
and enters the water table
• Zone of Saturation - below
the water table surface
where voids (spaces
between rock) are filled
• Water Table - the surface
of the zone of saturation
• Zone of Aeration – above
the water table surface
where voids are not filled
• Aquifer - porous sand, gravel or bedrock
through which groundwater flows
• Recharge area - an area of land through
which water passes downward or laterally
into an aquifer
– Natural recharge (via percolation) or lateral
recharge (recharge from the side)
• Water mining - removal of water from an
aquifer that exceeds its replenishment
• Surface runoff: water that flows into streams,
lakes, and reservoirs
– Reliable runoff: stable source of water not lost to
seasonal flooding and is available for human use
– 1/3 of all runoff is reliable; 2/3 is lost.
• Watershed (drainage basin): region from
which water drains into a stream, lake, or
World’s Reliable Runoff?
• In the last century, the population is tripled.
• Global water withdrawal has increased 7x;
per capita withdrawal has increased 4x
• We currently withdrawal 34% of the
world’s reliable runoff.
• It could reach 70% by 2025 but at this rate
it could reach as high as 90%.
How do we use our water?
• Current usage of water withdrawals
– 70% is used for irrigation (agriculture)
– 20% is used for industry
– 10% is used for city and residential
Interesting Factoids: It takes
2400 bathtubs of water to make one car.
25 bathtubs of water to make a t-shirt
37 gallons of water to produce one cup of coffee
US Freshwater Resources
• Much available water is:
– In the wrong place at the wrong time (flooding,
– Contaminated by agricultural and industrial
Water Use in the U.S.
• ½ the water in the US comes from groundwater
• Water tables in 48 states is dropping quickly.
• 36 states will suffer water shortages by 2013
– Population growth & Urban sprawl
– Drought, rising temperatures
– Excessive use
US Water Problems
Eastern US Western US
• Water used for: • Water used for:
energy production, irrigation (85%)
cooling, and • Water Problems:
manufacturing – Shortage of runoff due
• Water Problems: to low precipitation,
– Flooding high evaporation rates,
and prolonged drought
– Occasional urban
Population and Water Resources
Developed Countries Developing Countries
• People live where • Settle where water is
climate is more prevalent
favorable • Dry seasons make
• Water is imported crops difficult to grow
from other watersheds • Too expensive to
Using Dams and Reservoirs
• Purpose – capture and store runoff and
release it as needed for flood control,
producing hydroelectric power, supplying
• Problems – can reduce downstream flow to
a trickle; can reduce biodiversity; can
Causes of Freshwater Shortages
• Dry Climate
• Drought – over 21 days of lowered precipitation
and increased evaporation
• Desiccation – drying of soil due to activities like
deforestation and overgrazing
• Water Stress – lower per capita availability of
water; have more people who are using limited
About 41% of the world’s population lives in countries
that are water-scarce or water-stressed
What’s the answer to the increasing
water shortage problem?
• Withdraw groundwater?
• Build dams or reservoirs that store runoff?
• Bring in surface water from another
• Convert salt water to freshwater through
• Waste less water?
• Import food to reduce water use?
Problems with Groundwater
Groundwater over-pumping can cause land to sink, and
contaminate freshwater aquifers near coastal areas with
Provides water Flooded land
for year-round destroys forests or
irrigation of cropland and
cropland displaces people
Large losses of
Reservoir is estuaries are
useful for deprived of
recreation and nutrient-rich silt
Risk of failure
Can produce and
flooding is Migration and
reduced spawning of
some fish are
Fig. 13-12 p. 325
The Colorado River Basin
• 1400 miles of river through 7 states into the Gulf
• Has 14 major dams and canals that irrigate
• Supplies water to some of the driest land in the
rain shadow of the mountains.
Hoover Dam – Ansel Adams
Hoover Dam from above
Hoover Dam inlets
China’s Three Gorges Dam
• The World’s largest hydroelectric dam, which
will reduce China’s dependency on coal.
• Reduction in CO2 emissions.
• Facilitate the movement of cargo ships.
• Built to prevent flooding that killed 4000 in 1998.
China’s Three Gorges Dam
• Many freshwater fish and plants endangered or
• Cost is about $25 billion dollars.
• The reservoir will flood 1,350 villages and
displace 5.4 million people.
• Reduces nutrient rich sediments from going
• Built on a fault line.
• Over time, it will develop into a large sewer.
Three Gorges Dam
Three Gorges Dam construction
Three Gorges Dam
California Water Project
• A massive transfer of water from water-rich northern
California to water-poor southern California is
• Southerners need the water for irrigation of water thirsty
crops like rice and alfalfa.
• Northerners complain that the project will degrade the
Sacramento River and fisheries. Decreased water flow
reduces the ability of the river to flush out San Francisco
Bay. They also complain that Southerners are wasting the
Other Water Transfers
• Aral Sea
– Water was diverted
– Due to dry climate
the Aral Sea has
shrunk and salinity
North Aral Sea recovery 2005-07
China’s South-North Water Transfer
• China spent $62.5
billion to build canals,
reservoirs, dams and
pumping stations to
transfer water from the
Yangtze River to the
north to Beijing.
• Distillation: Heating water until it evaporates.
• Reverse osmosis: Forcing water through a
filter to remove salt.
• Desalination is very expensive
• Produces briny wastewater.
• Reverse osmosis water reduces soil salinization on
Using Water More Sustainably
Currently 65-70% of water people use throughout the
world is wasted through evaporation, leaks and other
It’s thought that if we can reduce the water loss by 15%,
we can meet the world’s water needs in the future.
Reasons for water waste
Water is cheap
No government subsidies for conserving water.
Improving Irrigation Efficiency
• 60% of the world’s irrigation water never
reaches the target crop.
More efficient irrigation methods:
• Gravity Flow = 60 – 80% efficient
• Drip irrigation = 90 – 95% efficient
• Center-pivot, low pressure sprinklers sprays water directly
onto crop. 80% efficient, but can be up to 95% efficient with
LEPA (low energy, precision application) sprinklers.
(efficiency 60% and
80% with surge
Water usually pumped
Above- or below-ground from underground and
pipes or tubes deliver sprayed from mobile
Water usually comes from water to individual plant boom with sprinklers.
an aqueduct system or a roots.
Getting More Water for Irrigation in
The Low-Tech Approach
• low-tech methods to
• Harvesting rainwater
Raising the Price of Water:
A Key to Water Conservation
• We can reduce water use and waste by raising
the price of water while providing low lifeline
rates for the poor.
– When Boulder, Colorado introduced water meters,
water use per person dropped by 40%.
What Can You Do?
Water Use and Waste
• Use water-saving toilets, showerheads, and faucet aerators.
• Shower instead of taking baths, and take short showers.
• Stop water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Flush toilets only when necessary.
• Wash only full loads of clothes or use the lowest water-level for smaller
• Use recycled (gray) water for lawn, gardens, house plants, car
• Wash a car from a bucket of soapy water, and use the hose for rinsing
• 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 and
decorative gravel or rocks.
• Water lawns and gardens in the early morning or evening.
• Sweep or blow off driveways instead of hosing off with water.
• Use drip irrigation and mulch for gardens and flowerbeds.
Natural phenomena Aggravated by
Renew and replenish human activities
Fig. 15.24, p. 327
TOO MUCH WATER
• Comparison of St. Louis, Missouri under
normal conditions (1988) and after severe
• The average American uses 90 gallons of water
each day. European-53 and Sub-Saharan
• Fix leaks, replace old toilets (trade ins),
efficient washers (50% less water and energy).
• A switch to water efficient appliances family of
4- save 23,000 gallons a year.