Transcript Water Resources ppt - Science with Horne

Chapter 14
WATER RESOURCES
Case Study: Water
Conflicts in the Middle
East
•Most of the water in the middle east comes
from three shared river basins: the Nile,
Jordan, and Tigris-Euphrates.
•Most likely in the future, these water short
countries are going to face conflicts over
access to water resources.
•The water from the Nile
River is used by three
countries: Ethiopia,
Sudan, and Egypt. Since
Ethiopia’s population is
rapidly increasing, they plan
to divert more water from
the Nile, along with Sudan.
•The Jordan basin is the
most water short region
and has competition
between Jordan, Syria,
Palestine, and Israel. Syria
plans to build dams and
withdraw more water from
the Jordan River, decreasing
the downstream water
supply for Jordan and Israel;
where Israel threatens to
destroy the dam.
Water Conflicts in the
Middle East (continued)
•Turkey is in control of the
Tigris Euphrates river,
controlling how much water
flows down stream to Iraq
and Syria before it empty’s
into the Persian Gulf.
•Turkey is building dams, and
if these dams are complete, it
will reduce the flow of water
downstream to Syria ad Iraq
by 35%.
Water’s Importance and Unique
Properties
-Keeps us alive
-Moderates
climate
-Sculpts the land
-Removes and
dilutes wastes and
pollutants
71% of the Earth’s surface is water
Properties of Water
• Water exists as a liquid
because of the strong
hydrogen bonds
between water molecules
• Water moves easily-from
one physical state to
another, and from one
place to another.
• Water slowly absorbs and
releases large quantities
of energy.
• Water is a superior
solvent.
• Makes up all living things.
•Water filters out
wavelengths of the suns UV
radiation that would harm
some aquatic organisms
•Attractive forces between the
molecules of liquid water
cause its surface to contract
and to adhere to and coat a
solid.
•Water expands when it
freezes.
Water Supply & Use
The Story of
Drinking Water
Online Game
(Quiz yourself!)
 Comparison of
population sizes and
shares of the world’s
freshwater among the
continents.
What is Groundwater?
 Ground water is one of the most important sources of water on earth
it contains more water than any other source of fresh water. It’s
the precipitation that infiltrates and percolates through the
voids in soil and rock.
• Zone of aeration- Close to the surface; pores of soil contain a
mixture or air and water
• Zone of saturation- lower layers of soil where spaces between
particles are completely filled with water.
• Water table- located at the top of the zone of saturation; top of
zone levels rises in wet weather and falls in dry.
• Porosity/Permeability
Groundwater
Groundwater
Animation
Aquifers
 Porous, water-saturated layers of sand, gravel or
bedrock through which groundwater flows; like a
flowing “river under the ground”
 Area of land that supplies water to aquifer is called the
recharge area
 Natural recharge is when water percolates downward,
but sometimes lateral recharge occurs
 Confined aquifers- bounded above and below by less permeable bedrock;
confined by pressure
 Unconfined aquifers- contains the water table
Journey through the Edwards
Aquifer video
Where is our water going?
•Most of the fresh water being
used up is to irrigate croplands
(70% ) and industries use up
20%, and cities/residences use
up only 10%.
• Some parts of the U.S such as
the eastern states get plenty of
irrigation, while western states
are very dry, while other states
have contaminated aquifers.
• This problem may cause “water
wars” in the future because
developing urban areas are in
need of water. (ie.
California/Arizona and Middle
East)
Cooling towers of
power plants
Too little Water
•There are four causes of water
scarcity:
1) Drought – prolonged period of low
precip., high evapor. rate
2) Dry climate
3) Desiccation- drying of exposed soil
due to deforestation/overgrazing
4) water stress – increasing #’s of
people relying on limited runoff
•The volumes of some of the worlds
lakes and rivers have shrunk drastically
because mostly because of human
withdrawals of water for irrigation
and for industry.
•About 1/6 of the percent of people on
this earth do not have enough access to
fresh water, and it is believed that will
continue to increase.
Global Water Shortage
We can increase water supplies by building dams,
bringing in water from elsewhere, withdrawing
groundwater, converting saltwater to freshwater and
importing food.
Who owns water???
•There is major
controversy of whether
water supplies should
be owned and managed
by governments or by
private corporations.
•Governments hiring
private companies to
manage water resources
must set standards and
maintain strict oversight
of such contracts.
The movie
F.L.O.W. – For
the Love of Water
How can we increase our
freshwater supplies?
1.
2.
3.
4.
5.
6.
Dams and reservoirs
Transporting surface water
Withdrawing groundwater
Desalination
Water conservation
Better use of natural hydrologic cycle
Using Dams and Reservoirs
to Supply More Water
Advantages:
Disadvantages:
 Cheap, constant electricity
 Displaces people
 Reduces downstream
 Disrupts aquatic ecosystems
flooding
 Storing water year-round for
irrigation and cities.
 Reservoirs can provide
recreational activities
(i.e. fish migrations/ runoff )
 Flooding can destroy
surrounding forests and
croplands
 Large loss of water through
evaporation
 Reservoirs behind dams
collect increased levels of silt
and slow water flow.
Colorado River Basin
•Colorado River has so many dams
it doesn’t reach the ocean.
•Used for hydroelectricity, irrigation (80%)
and recreation (whitewater rafting, camping, fishing)
for over 7 states.
Lake Mead at Hoover Dam, October, 2007.
According to Scripps researchers, Lake Mead
could be dry by 2021 if climate changes as
expected and future water usage is not curtailed.
Photo courtesy of Dr. Ken Dewey, Applied
Climate Sciences Group, University of Nebraska,
Lincoln
China’s Three Gorges Dam
Good News:
•Provide electricity of 18 coal
burning plants and reduce
China’s dependence on coal
•Larger ships can enter interior =
less in transportation costs
•Reduce greenhouse gas
emissions
•Improve air quality
Bad News:
• 1.9 M people being
relocated
•Build over a seismic
fault
•Flooding potential
•High costs
Transferring Water from One Place to Another
 Moving water from water-rich areas to water-poor
through tunnels, aqueducts, and underground pipe
can be helpful and harmful.
 Case Studies showcasing this include the Aral Sea, the
California Water Project, and Canada’s James Bay
Watershed.
Case Study: Siberia’s Aral Sea Disaster
 Aral Sea was once the world’s 4th largest freshwater
lake.
 Since 1960, enormous amounts of irrigation water have
been diverted from the inland Aral Sea and its two
feeder rivers, resulting in a large-scale water transfer
project for irrigation of cotton and rice cropland.
 This large-scale water diversion project, coupled with
droughts and high evaporation rates in this area’s
hot and dry climate, has caused a ecological,
economic and health disaster.
Aral Sea
Led to 85% loss of
wetlands loss of
major birds and
mammals in the area
Salt concentrations
increase decrease
in fish pops. and
spreading of salt to
croplands and
glaciers
Increase in salt,
dust and toxic
contaminants in Aral
Sea watershed has
led to health
problems.
*In 1999, UN and World Bank stepped
in and spent $600M to purify drinking
water and upgrade irrigation and
drainage systems.
Case Study: The California Water Transfer
Project
 This project uses a maze of giant dams, pumps, and
aqueducts to transport water from water-rich northern
California to southern California’s heavily populated
arid and semi-arid agricultural regions.
 It could degrade the Sacramento River, threaten
fisheries, and reduce flushing action that helps clean
San Francisco Bay of pollutants.
Withdrawing Groundwater
 Most aquifers are renewable sources unless the water
is removed faster than it is replenished or
becomes contaminated. WATER MINING
 Aquifers provide drinking water for about one-fourth
of the world’s population.
 In U.S., groundwater is being withdrawn at 4x’s its
replacement rate.
 Bad news: the water tables are falling in many areas of
the world as the rate of pumping out water exceeds
the rate of natural recharge from precipitation. (mostly
for crop irrigation)
Aquifer Depletion from Groundwater
Overdraft in the United States
Other Effects of Groundwater Overpumping
 Groundwater
overpumping
can cause land
to sink, and
contaminate
freshwater
aquifers near
coastal areas
with saltwater.
(Saltwater
Intrusion)
Case Study: The Shrinking Ogallala Aquifer
 Pumping water from the world’s largest aquifer has
greatly increased food production, but over pumping
is a serious problem in some areas.
 Transformed the most arid areas of the midwest, into
the most productive agricultural regions in the United
States.
Ogallala
Aquifer
SOLUTIONS
Groundwater Depletion
Prevention
Control
Waste less water
Raise price of water
to discourage waste
Subsidize water
conservation
Tax water pumped
from wells near
surface waters
Limit number of wells
Set and enforce
minimum stream flow
levels
Do not grow waterintensive crops in
dry areas
Divert surface water
in wet years to
recharge aquifers
Fig. 13-11, p. 324
Converting Saltwater to
Freshwater
 Removing saltwater from seawater will probably not be
done widely because of high costs and what to do
with the resulting salt.
 Ways to desalinate seawater include:
 Distillation- heat saltwater until it evaporates, leaves behind
salts, and collect freshwater in cooler condensation chamber.
 Reverse osmosis- pumping saltwater at high pressure through
a thin membrane that forces fresh water through, but traps salt
solutes.
 15,000 desalination plants in 125 countries
Major Problems with Desalination
 High cost
 Death of marine organisms
 Large quantity of brine wastes
 Future economics
Ashkelon Plant supplies 15%
of Israel’s Households
water needsLargest plant in 2005
Seeding Clouds and Towing
Icebergs and Big Baggies
 Seeding clouds with tiny particles of chemicals to
increase rainfall, or towing icebergs or huge bags filled
with freshwater to dry coastal areas, probably will not
provide significant amounts of fresh water in the
future.
 Bad News:
 Cloud seeding does not work very well in very dry areas
where rain is needed most, because there are few clouds.
 There is no compelling scientific evidence that it works.
 Introduces large amounts of chemicals to soil and water
 Legal disputes over ownership of cloud water.
Major Irrigation Systems
Gravity Flow: efficiency 60% and 80%
with surge valves. Water usually comes
from an aqueduct system or a nearby
river.
Drip Irrigation:
MOST EFFICIENT!
Center Pivot: low efficiency. Water
usually pumped from underground
and sprayed from sprinklers.
Too Much Water
 Flooding is caused by increased precipitation and
human impacts on earth.
 Used to occur every 50 years but now come about every 4
years
Rapid population growth, deforestation,
overgrazing , unsustainable farming on steep and
easily erodible mountain slopes
Hillside Before and After Deforestation
Floodplain- when a stream overflows and spills
over into surrounding land area
Benefits of Floodplains
 Highly productive wetlands
 Provide natural flood and erosion control
 Maintain high water quality
 Recharge groundwater
 Fertile soils
 Nearby rivers for transporation use and recreation
 Flatlands for urbanization and farming
Dangers of Floodplains and Floods
 Deadly and destructive
 Human activities worsen floods
 Failing dams and water diversion
 Hurricane Katrina and the Gulf Coast
 Removal of coastal wetlands
Case Study: Floodplains of Bangladesh
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Dense population
Located on coastal floodplain
Moderate floods maintain fertile soil
Increase frequency of large floods
Development in the Himalayan foothills
Destruction of coastal wetlands
In struggle to survive, the poor in Bangladesh have cleared many of the
coastal mangrove forests for fuel woods, farming, and aquaculture
ponds for raising shrimp. This has led to more severe flooding.
How Can We
Use Water
More
Sustainably?
Take the home water
audit quiz online to
see how much water
YOU use!