CHAPTER
14
Water Resources
Looking for Water . . .
in the Desert
• The 2300-kilometer Colorado River once flowed deep and wide
across the Southwest to Mexico’s Gulf of California.
• Since the Colorado River Compact, in 1922, seven states—
Arizona, California, Colorado, Nevada, New Mexico, Utah, and
Wyoming—have relied on the river’s water for human use.
• Today, drought, dams, and diversion have caused the once-raging
Colorado River to run nearly dry.
• Las Vegas, Nevada city officials have turned to an unlikely source
for water—the desert.Their proposal to mine groundwater from
beneath a scenic area of the Great Basin Desert is controversial.
Talk About It Is the human need for fresh water
reason enough to mine in an area that may
threaten area ecology? What other ideas might
states in the Colorado River Basin try?
Lesson 1.1 Earth: The Water Planet
Although the vast majority of Earth is covered in
water, one in eight people lacks access to clean
freshwater.
Objectives
• Discuss how fresh water can be both renewable and
limited
• Explain the significance of a watershed
• Explain how most groundwater is accessed
Water, Water Everywhere
• Water is everywhere
• Falls from sky as rain and snow
• Covers Earth’s poles as ice
• Fills oceans
Lesson 14.1 Earth: The Water Planet
Where Is Our Water?
• Fresh water a
renewable resource
• Water cycle constantly
recycles water
• Cycling water redistributes
heat, erodes mountain
ranges, builds river deltas,
maintains organisms and
ecosystems, shapes
civilizations
• As water cycles, it
changes state but very
little is gained or lost
Where is Our Water?
• Fresh water is a limited resource
• Some water is unusable for human
needs
• You can’t water crops with ice
• You can’t drink salt water
• Less than 0.5% of Earth’s water is
fresh and liquid
Did You Know? If all Earth’s water were in a two-
liter bottle, only about two capfuls would be
fresh, liquid water.
Where is Our Water
• Fresh water is a limited resource
• People do not always live in areas with ample access to water
• Some places have high population density but not a lot of water
• Other places have plenty of water but not a lot of people
• Parts of the world experience rainy and dry seasons
• Even if fresh water is available, it may not be available when
needed
Lesson 14.1 Earth: The Water Planet
Surface Water
• Surface water includes still bodies of waters and river
systems.
• Sources of surface water include rainfall & melting snow/glaciers/ice caps
• Water travels from source to body of water as runoff
• Water that flows over land and has not been absorbed into the ground
• Watershed – all of the land area that supplies water to a particular river system
• Imagine tracing the path of a drop of water in a river to where it fell as
precipitation
Did You Know? The Mississippi River Basin
covers 3 million square kilometers (1.2 million
sq mi), making it the third largest watershed in
the world. It drains 41% of the land area of the
contiguous US.
Surface Water
•Each watershed is
made up of many
smaller watersheds
•Watersheds are
interconnected
•Managing water
sustainability requires
the cooperation of
everyone living within a
watershed
Watersheds of the U.S.
Groundwater
• Ground water – precipitation that did not evaporate,
flow into a river, or get taken up by organisms; instead
seeped downward through soil
• Permeable layer – rock and soil containing spaces or pores
through which water can pass
• Impermeable layer – few or no pores
• Aquifier – sponge-like formations of rock, sand, or gravel that
hold water
• Zone of aeration – aquifier’s upper layer that has pores water
can flow through
• Zone of saturation – aquifier’s lower layer pores are completely
filled with water
• Makes up about 1/5th of Earth’s freshwater supply
Lesson 14.1 Earth: The Water Planet
Groundwater
• The water table
separates the zone of
saturation from the
zone of aeration.
• Affected by shape of land
and amount of water
available
• Recharge zone – any
area where surface
water soaks into the
ground and reaches an
aquifer below
An Aquifer
Did You Know? The average age of groundwater
is 1400 years. Groundwater recharges very slowly.
Lesson 14.1 Earth: The Water Planet
Groundwater
• Aquifers release 1.9 trillion L
(492 billion gal) of groundwater
to the surface each day via
springs, geysers, and wells.
• World’s largest aquifer is
Ogallala under the Great
Plains
• Enables American farming
Old Faithful, a well-known geyser in Yellowstone National Park, shoots
groundwater over 100 feet into the air many times a day.
Lesson 14.2 Uses of Fresh Water
One third of all the people on Earth
are affected by water shortages.
Objectives
• List the three primary categories of freshwater use
• Relate the causes of surface water depletion to their
effects
• Explain the major causes and effects of groundwater
depletion
• Describe strategies for addressing water depletion
Lesson 14.2 Uses of Fresh Water
How We Use Water
• Three main uses of fresh
water include:
• Agricultural (70%)
• Industrial (22%)
• Personal (8%)
Did You Know? The average
American uses 250 L of fresh water a
day for personal uses, such as
bathing and brushing teeth.
How We Use Water
• Agriculture
• 400 gallons of water are needed to produce 2.2 lbs of wheat
• 3,960 gallons of water are needed to produce 2.2 lbs of grainfed beef
• Industry
• A standard bottle of water requires twice as much water to
produce than it holds
• American factories use 18 billion gallons of water everyday to
make and transport products
• Water used in power plants that generate electricity to cool
machinery
• In the refining process, 1 – 2.5 gallons of water is needed to
refine a gallon of gasoline
How We Use Water
• Personal
•
•
•
•
•
•
•
Average person in U.S. drinks 2-5 liters of water
10 minutes shower = 40 gallons
Flushing a toilet = 6 gallons
Dishwasher = 6 gallons
Watering the average suburban lawn = 750 gallons
Filling the average swimming pool = 19,000 gallons
Personal water uses inside the home are called residential
uses
• Leaky pipes = 9.5 gallons a day
Lesson 14.2 Uses of Fresh Water
Using Surface Water
• Most freshwater used in the U.S. is surface water. (77%)
• Water Diversion – moving water from its source to places where
humans use it
• Surface water is diverted by canals and dams.
• Drought and overuse have caused significant surface water depletion.
Did You Know? The Aral
Sea was once the fourth
largest body of fresh water.
Aral Sea, 1997
Aral Sea, 2009
Using Surface Water
Benefits of Dams
• Clean power generation
• Crop irrigation
• Flood control
• Shipping
• New recreational
opportunities
Costs of Dams
• Habitat alteration
• Fisheries decline
• Population displacement
• Sediment capture
• Loss of fertile farmland
• Risk of failure
• Lost recreational
opportunities
Lesson 14.2 Uses of Fresh Water
Using Groundwater
• Groundwater recharges very slowly
• Longer to replace a given amount of water taken from an
aquifer than a lake or pond
• Ground water use is unsustainable
• 68% of groundwater in the U.S. is used for irrigation,
most of which is very inefficient.
• Half a football field of irrigated land for each person
• Irrigated land has nearly doubled since 1960 because of
population growth
• Water lost to runoff and evaporation
Using Groundwater
• Groundwater mining turns groundwater into a
nonrenewable resource because it is withdrawn from
the ground faster than it can be replaced.
• When groundwater is depleted, the falling water
tables can cause cities to sink, and undrinkable
saltwater to move into the depleted aquifers.
Lesson 14.2 Uses of Fresh Water
Solutions to Freshwater Depletion
• Increase supply:
• Desalination: “Making” fresh water by removing salt from saltwater.
• Expensive, requires a lot of energy, produces concentrated salty waste
• Reverse osmosis: Forcing saltwater through artificial membranes to
filter out salt
Desalination
Solutions to Freshwater Depletion
• Decrease demand:
• Agricultural:
• Drip-irrigation
• reduces water loss due to evaporation and runoff
• Can cut agricultural water use in half
• climate-appropriate plants
• Industrial: Water-conserving processes, recycling
wastewater to cool machinery.
• Personal:
• Xeriscaping – Reduce outdoor water consumption by choosing
outdoor plants adapted for arid conditions
• Water conservation – low flow toilets, faucets, showerheads,
appliances
Lesson 14.3 Water Pollution
3,800 children die every day
from diseases associated with
unsafe drinking water.
Objectives
• Discuss the main categories of water pollution
• Explain why groundwater pollution is difficult to clean
up
• Discuss the sources and effects of major pollutants
found in the ocean
• Describe how water is regulated and treated
Lesson 14.3 Water Pollution
Types of Water Pollution
• Point-source pollution:
From a discrete location,
like a factory or sewer pipe
• Nonpoint-source
pollution: From many
places spread over a large
area, such as when
snowmelt runoff picks up
pollutants along its path
Point source oil pollution
Oil after a spill, Trinity Bay, Texas
Lesson 14.3 Water Pollution
Nutrient Pollution
THE PROCESS OF
EUTROPHICATION
Nutrients
build up in
water.
• Excess phosphorous and other
nutrients in the water is nutrient
pollution.
• Eutrophication occurs naturally, over a
long period of time, sometimes
centuries
• Eutrophic in Greek means “good food”
• Sped up by humans
Algae and
aquatic plant
growth
increases.
Organisms die.
Decomposition
requires
oxygen.
Dissolved
oxygen levels
decrease.
Nutrient Pollution
• Cultural/Artificial Eutrophication
• Nutrient pollution by humans
• Typically occurs from phosphorus-rich fertilizers and
detergents in runoff or wastewater
• Algal Bloom – sudden explosion of algae growth
• Can be thick and cover water’s surface preventing sunlight
from reaching plants below causing them to die
Lesson 14.3 Water Pollution
Toxic Chemical Pollution
• Occurs when harmful
chemicals are released into
waterways
• Can be organic or inorganic
• Organic – petroleum,
petroleum based products,
fertilizers, detergents
• Inorganic – mercury, arsenic,
lead
• Harms ecosystems and
causes human health
problems
Lesson 14.3 Water Pollution
Sediment Pollution
• Sediment pollution:
• Unusually large amounts of sediment that change an
aquatic environment
• Results from erosion.
• Large-scale land clearing, mining, clear-cutting, clearing land to build
houses, careless farming practices
• Can degrade water quality, cause photosynthesis rates to
decline as water clouds up, and disrupt food webs
Thermal Pollution
• A heat source that raises the temperature of a
waterway
• Water used for cooling industrial processes and power plants
• Removal of trees or plants that provide shade
• Heated water holds less oxygen.
Lesson 14.3 Water Pollution
Biological Pollution
• Biological pollution occurs when
pathogens (disease causing
organisms and viruses) enter a
waterway.
• Can be caused by human and
animal waster
• Biological pollution causes more
human health problems than any
other form of water pollution.
Cholera bacteria
Did You Know? Giardiasis is
the most common form of
waterborne disease in the U.S.
• Water treatment reduces
biological pollution.
Lesson 14.3 Water Pollution
Groundwater Pollution
• Sources of groundwater pollution
include
• natural sources
• Aluminum, flouride, nitrates, sulfates
occur naturally in groundwater but are
toxic at high concentrations
• surface pollutants leaching through soil
• Chemicals in fertilizers, pesticides
• leaky underground structures.
• Wells, leaky storage tanks, sewage,
gasoline
Did You Know? The EPA repairs and replaces leaky
underground gas storage tanks to reduce
groundwater pollution. Over the last 25 years, over
1.7 million tanks have been repaired or replaced.
Acid drainage from a coal mine
Groundwater Pollution
• Chemicals break down more slowly in groundwater
than in surface water.
• Groundwater contains less dissolved oxygen, microbes,
minerals, and organic matter so decomposition is slow
• DDT banned in 1972 still found widely in U.S. aquifers
• Alachlor (herbicide) declines by 50% after 20 days in soil; in
groundwater, the same decline takes 4 years
• Most efforts to reduce groundwater pollution focus on
prevention.
Lesson 14.3 Water Pollution
Ocean Water Pollution
• Common practice to dump trash
and sewage into ocean
• Oil pollution in the ocean comes
from many widely spread small
sources; not large tanker spills.
• Leakage from boats
A 2004 oil spill off the Alaskan coast
• Runoff from human activities
• Natural seeps
Did You Know? According to the U.S. Oil
Pollution Act of 1990, by 2015, all oil
tankers in U.S. waters must have double
hulls to help prevent against leaks.
• Naturally occurring deposits on the
sea floor
• Largest single source (46%)
Mercury and Nutrient Pollution
• Ocean organisms bioaccumulate mercury pollution.
• Swordfish, shark, albacore tuna
• Mercury causes neurological damage especially in fetuses,
babies, and children
• Nutrient pollution can cause red tides.
• Algae produces red pigments
• Caused by excess nitrogen
• Closes beaches, stops fishing
Lesson 14.3 Water Pollution
Controlling Water Pollution
• Legislation, technology, &
citizen action all help
decrease water pollution.
• The Clean Water Act
Lake Erie
• Set water pollution
standards
• Required permits to release
point-source pollution
• Funded sewage treatment
plant construction
Did You Know? The Great Lakes show that humans can
change their ways and clean up trouble spots. In the
1970s, Lake Erie was declared “dead” but is now home
to some flourishing species, especially the walleye.
Lesson 14.3 Water Pollution
Water Treatment
• Drinking water is treated to remove pollutants before
humans consume it.
• Wastewater is treated to remove pollutants before humanused water is released back to the environment.
Septic systems are the most popular method of
wastewater disposal in rural areas of the U.S.