WATER
Teacher Guide
including
Lesson Plans, Student Readers, and More Information
Lesson 1 - Importance of Water
Lesson 2 - Water Properties (Lab)
Lesson 3 - Water Chemistry (Lab)
Lesson 4 - Movement of Water
Lesson 5 - Watersheds
designed to be used as an Electronic Textbook
in class or at home
materials can be obtained from the Math/Science Nucleus
Math/Science Nucleus © 2001
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EARTH SCIENCES - WATER
Lesson 1 - Importance of Water
MATERIALS:
reader
Objective: Students learn why water is
critical to all life.
Teacher note
The Earth is a dynamic system, spinning on its axis as it revolves around the
Sun. The surface of the Earth, which includes the atmosphere, hydrosphere, and
lithosphere, responds to this movement in space. The interaction of these spheres
creates the life sustaining water cycle. Water has not always been on this planet.
Oceans were created over eons of time as hydrogen and oxygen were united inside
the Earth to form water. Volcanic events over a long span of time have "outgassed"
much of this water in the form of steam. The steam formed clouds in the
atmosphere and precipitation brought the water back to Earth, to continue the
endless water cycle. The miracle of water then created conditions for life to develop
and survive on this planet.
Water is a transparent, odorless, tasteless liquid at normal Earth
temperatures. It illustrates three states of matter including liquid (water), solid (ice),
and gas (steam). Another chemical quality of water is its very large heat capacity,
meaning that it can absorb a great deal of heat without, itself, becoming extremely
hot. This fact makes the oceans a large reservoir of heat, which greatly effects the
overall weather and climate patterns of the world.
Water is a peculiar substance with properties that make it an ideal fluid. If
you calculated the boiling and freezing temperature of water, you would find that
water has an unusually low freezing point and a high boiling point compared to other
compounds.
In the upcoming units students will learn that water is important to our very
existence. The fluid is so unique that without it, life as we know it would not be able
to function. With the miracle of life, also come a tragic side. Water borne diseases
and other pathogens are transferred by water and effect many areas. These
diseases cause more death than any other cause in the world.
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Water is our lifeline that bathes us and feeds
us. In ancient cultures water represented the very
essence of life. The Romans were the first to pipe
water into their growing cities, especially with their
aqueducts. They also realized that sewage water
could cause damage to their people, and needed to
be removed from large areas of people.
Water has played a role not only in the history
of countries, but in religion, mythology, and art.
W ater in many
religions cleanses
the soul through holy
Ancient Roman aqueduct
water. For example,
the water at Lourdes, France is thought by many religions
to be sacred water with healing powers. In Egyptian
mythology, the Nu was the beginning of everything and
represented water. It brought life to their people, but in
drought, produced chaos.
Water has always been perceived as a gift from the
gods as it rained from the heavens.
The water or hydrologic cycle explains interactions between the atmosphere,
hydrosphere, and lithosphere. The water or hydrologic cycle is a major driving force
on our planet. Water is in constant motion, evaporating into the atmosphere from oceans,
lakes, rivers and streams. When the atmosphere can no longer support the moisture
within the clouds, we experience rain, snow, hail, or sleet. Some water is locked in the
form of ice at the polar caps and in glaciers.
Water melts in the spring, producing
runoff, that percolates through the Earth
as groundwater (subsurface) or makes its
way back to the sea (surface). The oceans
contain most of the water, but it is salt
water which is unuseable by most
organisms. Only pure H2O (water) can
interact with organisms.
The movement of the oceans also
has a direct effect on the atmosphere. The
atmosphere is that envelope of gas that
keeps organisms living on this planet.
Oceans and atmosphere interact to give us
weather.
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Water provides the Earth with the capacity of supporting
life. An organism doesn’t have to be told how important water
is to their existence. An amphibian knows to lay their eggs in
water or else there will be no new born. Even flies know to lay
their eggs in fresh water.
The only organism that doesn’t understand the
importance of water is humans, especially in industrialized
countries. Children in those societies turn on the water in a
sink and never think about the trouble someone has gone for
that “miracle” to occur.
In the United States it is
mandated by law that its citizens
should be given clean and
abundant water.
Dams,
reservoirs, filtering plants, and
pipes all bring clean water when
Dam in California
the facet is turned on. Sewage
water is only mixed with
recycled water supplies after the water goes through
rigorous cleaning methods. Water borne diseases do not
Entamoeba histolytica, an amoeba
effect the U.S. population like in other countries that do not causes dysentery
treat their water supply.
Water borne diseases are any illnesses caused
by drinking contaminated water. Diseases can include
infection from bacteria (Salmonella), viruses, or by small
parasites (Cryptosporida, Giardia, and Toxoplasma).
These organisms and viruses cause diseases like
cholera, typhoid fever, malaria, botulism, polio,
dysentery, giardia,
and hepatitis A. One
of the first symptoms of
Children with Schistosomiasis
these diseases is
diarrhea, which cause about three million deaths
throughout the world, mainly in India, Africa, and South
America.
Sewage is sometimes discharged into rivers,
where children downstream might be taking a bath or
using the water to drink. The simplest treatment method
is boiling. Just bring the water to a boil for at least one
Schistosomiasis worms, parasite in
water
minute, then allow it to cool. But this is not always
effective in heavily chemical polluted water supplies.
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Without water, organisms could
not exist. Water is a resource that
should not be taken for granted. It
needs to be conserved, just as we
save other valuable resources.
Water is one of the weirdest
compounds known to humans. The
difference between the boiling point
and freezing point of water is one of
the largest ranges of any compound. It
is this span of temperature that mirrors
the range of where life can exist, from
bacteria to humans. Water also has a
Water creates a stable environment
very high specific heat, which means
that it can absorb or lose much heat before its temperature changes. This is important in
maintaining body heat in mammals. It also takes a lot of energy before vaporization can
occur. For this reason, water evaporates slowly from ponds and lakes, where many life
forms are dependent on a stable, warm environment.
Water is less dense in its solid
state than in its liquid state, so that ice
floats instead of sinking. This property
permits life to develop in polar and
subpolar regions where ice floats and
allows life to continue living below the
surface. If ice were heavier than water,
it would sink, and more ice would form
on top of it. As a result, all life in the
waters would be trapped in the ice in the
many areas of the world where it gets
cold enough to freeze water.
Life is abundant under ice sheets
Water is a remarkable solvent, where most
elements and compounds can dissolve in its
powerful molecular structure. Gases such as
oxygen and carbon dioxide, can also dissolve,
making it readily available for photosynthetic
and nonphotosynthetic organisms to use.
Fish use dissolved oxygen to breathe
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Water also exhibits viscosity.
One can
observe the effects of viscosity alongside a stream or river with
uniform banks. The water along the banks is nearly still, while
the current in the center may be swift. This resistance between
the layers is called viscosity. This property allows smaller fish
to live near the shore, while larger fish are able to swim
efficiently in strong currents. Viscosity is also responsible for
the formation of eddies, creating turbulence that leads to good
mixing of air in the water and more uniform distribution of
microscopic organisms.
How water provides all these properties are complex, but
only emphasizes the importance of water to every organism on
Earth.
Resistance of water molecules creates uneven
movement
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EARTH SCIENCES - WATER
Lesson 2 - Water Properties
MATERIALS:
reader
pepper, water, bowls, detergent, a
capillary tube
Objective: Students experiment with
the chemical properties of water.
Teacher note
The next two labs will concentrate on water as a chemical substance. The
cohesive or attractive forces between liquid molecules are responsible for surface
tension. The molecules at the surface are attracted more to each other than those
internally. This forms a surface "film" which makes it more difficult to move an object
through the surface.
It would take a force of 72 dynes to break a surface film of water 1 cm long at
25LC. The surface tension of water decreases significantly with temperature. Hot water
is a better cleaning agent because the lower surface tension makes it a better "wetting
agent" to get into pores. Soaps and detergents further lower the surface tension.
Capillary action is the result of adhesion and surface tension. Adhesion of water
to the walls of the wall of a graduated cylinder will cause an upward force on the liquid
at the edges. It will form a meniscus which turns upward. The surface tension acts to
hold the surface intact, so instead of just the edges moving upward, the whole liquid
surface is dragged upward.
The surface tension of water provides the necessary wall tension for the
formation of bubbles with water. The tendency to minimize that wall tension pulls the
bubbles into spherical shapes (LaPlace's law).
Answers:
Experiment 1. The pepper will move away from the center, leaving a circle of clear
water. The detergent has reduced the surface tension in the center; the higher surface
tension remaining around the edge pulls the pepper particles toward the edge.
Changing the surface tension has caused motion.
Experiment 2. A capillary tube uses the principles of surface tension to make water
rise. Sucking will not be able to move it any faster.
Experiment 3:
You may want to have warm water all ready available in the classroom for Experiment
3. In this way, you can have the student teams perform Experiment 3 first before the
water cools and then continue to the other experiments.
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Water is a transparent, odorless, tasteless
liquid composed of the elements hydrogen and
oxygen. Water is an universal solvent, meaning
that many elements can be dissolved by water.
Fresh water has relatively few elements dissolved
in the water, while the oceans contain many
dissolved salts.
Water is important to our lives, and without
it we could not live. In fact, there are no living
creatures that can live without water. Water most
probably originated on this planet as gases were
emitted from volcanoes. The Earth's atmosphere
captured this water and has continuously recycled
3 forms of water: ice, water, and steam
it throughout time, in what is called the water cycle.
Water evaporates and forms clouds – the clouds provide rain and snow – which is
collected in rivers, lakes, underground reservoirs, and oceans – that are the source for
further evaporation. Water is the perfect substance for the water cycle, because it has a
high boiling point and a low freezing point.
The molecular structure of water resembles
that of a teddy bear’s head. The hydrogen and the
oxygen atoms have a very tight covalent bond
formed where the hydrogen and the oxygen share
electrons. Bonding between molecules of water is
called a hydrogen bond, which has a weaker
attraction. The hydrogen atoms of one water
molecule stick to the
oxygen atoms of
nearby
water
molecules. These
weak bonds are very
important for the
chemistry of life.
Molecules which
stick to water, such
as alcohol and sugar, are called hydrophilic, meaning
"water loving.”
Not all molecules are sticky. The scientific name is
hydrophobic which means "water fearing.” Examples of
slippery molecules are fats and oils.
Hydrogen bond
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Water exhibits surface tension. Surface tension
of water or the ability of a substance to stick to itself
makes water an excellent substance to float heavy
objects on its surface. The molecules of water on the
surface of a calm and quiet pond tend to be drawn into
the liquid, so that the liquid surface is taut, like a sheet
of rubber drawn over the open mouth of a jar. This
tautness is caused by surface tension.
Surface tension is responsible for the shape of
liquid droplets. Although easily deformed, droplets of
water tend to be pulled into a spherical shape by the
Droplets are caused by surface
cohesive forces of
tension
the surface layer.
The surface of water can support small objects like a
sewing needle until the surface tension is broken. This
"skin" on the water aids the growth of mayflies and
caddisflies that are attached to the water’s surface.
However, surface tension can also trap flying insects
that accidently fall into the water and are unable to fly
Caddisflies
out.
Soaps and detergents help the cleaning
of clothes by lowering the surface tension of the
water. This allows the water to soak into
pores and dirty areas more effectively. Small
insects such as the water strider can walk on
water because their weight is not enough to
penetrate the power of surface tension.
Common tent materials are somewhat
rainproof
because surface tension of water will
Capillary action
bridge the pores in the finely woven material.
But if you touch the tent material with your finger, you will break the surface tension and
the rain will drip through.
Water can defy gravity as it can “walk” up the sides of a thin tube. The molecule
is actually attracted to the side and pulls itself up. It might take a long time to get up a thin
capillary tube, but it is working against gravity.
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EARTH SCIENCES - WATER
PROBLEM: How can you explain different properties of water?
HYPOTHESIS:
MATERIALS: water, beaker, pepper, detergent, alcohol, capillary tube, washing soda,
rice, sugar
PROCEDURE: Experiment 1. Partially fill a glass with water. Sprinkle pepper all over
the surface. Now drip a drop of liquid detergent onto the surface, in the center of the
peppered area. Record what happens and why?
Drop a little alcohol on a peppered surface. What happens?
Experiment 2. Try and suck water through a capillary tube (like you would through a
drinking straw). What happens and why?
Experiment 3. Using 250 ml of water, try to dissolve 1 ml of salt, fine sand, tea leaves,
washing soda, rice, and sugar. Record what happens. Warm the water with a Bunsen
burner or heating surface. Try and dissolve the same amount of substance in warm water.
Record what happens.
SUBSTANCE
COLD
WARM
SALT
FINE SAND
TEA LEAVES
WASHING SODA
RICE
SUGAR
CONCLUSION: Identify the scientific principle in each experiment?
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EARTH SCIENCES - WATER
Lesson 3 - Water Chemistry (Lab)
MATERIALS:
reader
thermometer
La Motte Nitrate kit
La Motte Dissolved Oxygen kit
La Motte pH kit
Objective: Students learn the
procedure for pH, dissolved oxygen,
and nitrates.
Teacher note
There are many tests that can determine the components that are dissolved
in water. Water quality uses chemical analysis of water to collect and compare
data. Water testing is usually done over a long period of time and the scientists are
looking for unusual levels of different components.
You can even use this lab as a trial, and then students can conduct these
same tests on a nearby creek, river, or pond. Make sure that your students also
record any unusual conditions that might help to interpret the data. For example,
you have found a high level of copper in your water samples. In your notes you
wrote down that the sample site is near a heavily used roadway and that this was
the first rain. This would provide you with the information you need to determine
that the braking of the cars probably was the cause of the high copper content.
When you put your brake on, you scape off copper. The first rain concentrated the
copper levels from the roadway that were accumulating during the dry spell.
Problem solving is very important in water testing, and not just the individual
test. Emphasize with students about replication of sample, to make sure the data
is accurate.
In this exercise students learn about temperature, nitrate, dissolved oxygen,
and pH. Have them read the information and then have them all test the same
water. If you are using other test kits, change the worksheets accordingly. Discuss
with students any differences among the different data collected. Depending on
time, you can have the student replicate the same sample 3 times. Practice makes
perfect!
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Testing of water is important to humans
because we need clean, fresh water. Keeping
the water healthy for plants and other organisms
also provides recreational sports for humans.
Polluting our water supplies causes a ripple
effect that eventually harms the original
polluters.
Many people feel that just put a little oil in
the storm drain or riding gas driven boats on
drinking water reservoirs won’t hurt anything. If
Polluted water
only one person
polluted, maybe nothing would happen. But that is never the
case.
Humans were originally nomads because their water
and land would become polluted from their use. If you
defecated into your water supply, mysterious diseases would
occur. It took humans a long time before they figured out,
they were the ones causing the health problems.
This lab looks at testing temperature, dissolved
oxygen, nitrates, and pH of water. These are only four tests,
out of many, you can determine for water. Directions are on
your lab sheet. First, read the information on why these tests
are important and then perform the test.
Sampling water
Water temperature is an important factor for survival of
aquatic life. Very high and very low water temperature can kill many
aquatic plants and animals. The temperature can affect how an
organism’s internal mechanisms (metabolism) work. For example
salmon and trout prefer temperatures between (4.5° C) 40° and 20°
C (65° F). Different stages of the growth of fish are susceptible
ranges of fish. In the summer when temperatures are high, juvenile
fish actively look for the cooler pools of water. A fish must pump
water across its gills to meet its need for oxygen. If the dissolved
oxygen in water is low, the gills must
move faster to get enough oxygen for
the fish to survive.
Thermal pollution can occur
when heated water is discharged into
Industrial plants can cause
cooler streams or rivers. This heated
thermal pollution
water generally is from power plants
or industrial processes. If the water is not cooled down
before entering into a stream or pond, it can cause
organisms to die of increased temperature.
Gills beat faster in warm water
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A simple test to determine chemicals
dissolved in water that might be harmful to
organisms is pH. The percentage of free hydrogen
(H ) and a hydroxy ion (OH) determines the pH
of the liquid. Pure water (HOH) is made up one
part hydrogen and one part hydroxy and given a
neutral standing or a “7.” If you have more
hydrogen than hydroxy it is an acidic solution. If
the hydroxy ions, are greater than the hydrogen
ions you have a basic or alkaline solution. The
concentration of the hydrogen ions [H+] in a
solution determines the pH.
A pH of 6.0 to 9.0 is the range that fishes
and invertebrates can successfully survive. Each
species has its own tolerance level. The table
below gives some special effects of pH on fish and
aquatic life.
Minimum
Maximum
3.8
10.0
Fish eggs could be hatched, but deformed young are often produced
4.0
10.1
Limits for the most resistant fish species
4.1
9.5
Range tolerated by trout
4.3
Carp die in five days
4.5
9.0
Trout eggs and larvae develop normally
4.6
9.5
Limits for perch
5.0
Limits for stickleback fish
9.0
Tolerable range for most fish
8.7
Upper limit for good fishing waters
5.4
11.4
Fish avoid waters beyond these limits
6.0
7.2
Optimum (best) range for fish eggs
1.0
Mosquito larvae are destroyed at this pH value
4.7
Mosquito larvae live within this range
5.0
3.3
Effects
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Oxygen rich water
Although water is made of H2O, the oxygen is not
available for organisms. Dissolved oxygen in water is
required for most organisms. Dissolved oxygen (DO)
refers to the volume of oxygen that is contained in water.
Oxygen enters the water by photosynthesis of aquatic
plants and by the transfer of oxygen across the air-water
interface. The amount of oxygen that can be held by the
water depends on the water temperature, salinity, and
pressure. Gas solubility increases with decreasing
temperature (colder water holds more oxygen)
Flowing water is more likely to have higher
dissolved oxygen levels than is stagnant water because
of the water movement at the air-water interface. In
flowing water, oxygen-rich water at the surface is
constantly being replaced by water containing less
oxygen as a result of turbulence. Because stagnant water
undergoes less internal mixing, the upper layer of
oxygen-rich water tends to stay at the surface, resulting in
lower dissolved oxygen levels throughout the water
column.
Nitrogen is found in the cells of all living things and is a major component of
proteins. Nitrogen may exist in the free state as a gas N2, or as nitrate (NO3-), nitrite
(NO2-), or ammonia (NH3+). Organic nitrogen is found in proteins and is continually
recycled by plants and animals. Nitrogen is important to organisms, but too much can
cause damage.
Nitrogen containing compounds act as nutrients in streams and rivers. Nitrate
reactions in fresh water can cause oxygen depletion. Organisms depending on the supply
of oxygen in the stream will die. The sources of
nitrogen into bodies of water are municipal and
industrial wastewater, septic tanks, feed lot
discharges, animal wastes (including birds and
fish), and discharges from car exhausts.
Nitrites can produce a serious condition in
fish called "brown blood disease." Nitrites also
react directly with hemoglobin in human blood and
other warm-blooded animals to produce
methemoglobin. Methemoglobin destroys the
ability of red blood cells to transport oxygen. This
condition is especially serious in babies less than
three months of age. It causes a condition known
as "blue baby" disease.
Wastewater adds nitrogen in water
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EARTH SCIENCES - WATER
PROBLEM: Why should you test for pH, nitrates, and dissolved oxygen?
HYPOTHESIS:
MATERIALS: thermometer, La Motte test kits for pH, nitrate, and dissolved oxygen,
water samples
PROCEDURE: Use only with LaMotte kits and materials
pH Testing Procedure
1. Rinse each test tube with the water sample. Gloves should be worn to avoid skin
contact with the water.
2. Fill the tube to the 5mL line with sample water.
3. While holding a dropper bottle vertically, add 10 drops of Wide Range Indicator
Solution.
4. Cap and invert several times to mix.
5. Insert the tube into the Wide Range pH Comparator. Hold the comparator up to a light
source. Match the sample color to a color standard.
6. Record the pH value.
7. Wash your hands
Nitrate Testing Procedure
1. Fill the sample bottle with sample water. Use gloves if drawing the sample by hand.
2. Rinse and fill one test tube to the 2.5 mL line with water from the sample bottle.
3. Dilute to the 5 mL line with the Mixed Acid Reagent. Cap and mix. Wait 2 minutes.
4. Use the 0.1 g spoon to add one level measure (avoid any 50-60 times in one minute).
Wait 10 minutes.
5. Insert the test tube into the Nitrate Nitrogen Comparator. Match the sample color to a
color standard. Record the result as mg/L(ppm) Nitrate Nitrogen (NO3-N). To convert to
mg/Nitrate (NO3) multiply by 4.4.
6. Place the reacted sample in a clearly marked container. Arrangements should be made
with toxic material handlers for safe disposal. Please wash your hands after this water test
is completed.
Dissolved Oxygen Testing Procedure
1. If you have a barometer, record the atmospheric pressure. Remove the cap and
immerse the DO bottle beneath the river’s surface. Use gloves to avoid contact with the
river.
2. Allow the water to overflow for two to three minutes (This will ensure the elimination of
bubbles).
3. Make sure no air bubbles are present when you take the bottle from the river.
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4. Add 8 drops of Manganous Sulfate Solution and 8 drops of Alkaline Potassium Iodide
Azide.
5. Cap the bottle, making sure no air is trapped inside, and invert repeatedly to fully mix.
Be very careful not to splash the chemical-laden water. Wash your hands if you contact
this water. If oxygen is present in the sample, a brownish-orange precipitate will form
(floc). The first two reagents “fix” the available oxygen.
6. Allow the sample to stand until the precipitate settles halfway. When the top half of the
sample turn clear, shake again, and wait for the same changes.
7. Add 8 drops of Sulfuric Acid 1:1 Reagent. Cap and invert repeatedly until the reagent
and the precipitate have dissolved. A clear yellow to brown-orange color will develop
depending on the oxygen content of the sample.
8. Fill the titration tube to the 20 mL line with the “fixed”: sample and cap.
9. Fill the Direct Reading Titrator with Sodium Thiosulfate 0.025 N Reagent. Insert the
Titrator into the center hole of the titration tube cap. While gently swirling the tube, slowly
press the plunger to titrate until the yellow-brown color is reduced to a very faint yellow.
If the color of the fixed sample is already a faint yellow, skip to step 10.
10. Remove the cap and Tritrator. Be careful not to disturb the Titrator plunger, as the
tiration begun in step 8 will continue in step 11. Add 8 drops of Starch Indicator Solution.
The sample should turn blue.
11. Replace the cap and Titrator. Continue titrating until the sample changes from blue
to a colorless solution. Read the test result where the plunger top meets the scale.
Record as mg/L (ppm) dissolved oxygen.
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EARTH SCIENCES - WATER
DATA SHEET
Sample #
temperature
dissolved O2
nitrate
pH
Average
Describe conditions:
Describe water:
Conclusions:
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EARTH SCIENCES - WATER
Lesson 4 - Movement of Water
MATERIALS:
reader
Objective: Students learn
surface and ground water.
about
Teacher note
Water is a renewable, basic natural resource which is essential to all
organisms. Humans have trapped water for use in agriculture and industrial
activities. Our society can create large cities like New York and Chicago and create
reservoirs to service the people of those areas. More importantly, we have
developed ways to clean and reuse our wastewater. We have also learned that
deserts can become large metropolitan areas, like Los Angeles, if only we provide
water.
There are two sources of water that this reader summarizes, ground and
surface water. These two sources move in their own unique ways. Humans use
both surface and ground, but surface is much easier to control.
Runoff from surface water includes all surface flow through streams as
channel flow. Runoff is mainly derived from excess precipitation which does not
infiltrate into the soil to become groundwater. Groundwater recharges itself through
precipitation or pools of water (lakes, ponds) that percolate through the soil and
pores of rocks.
Water looks for different routes as it heads for sea level. The movement of
water and how it meandering through the land will define drainage systems or what
is referred to as watersheds.
Make sure students understand all the components of the water cycle. They
may have learned the easy processes of evaporation and precipitation, but in this
lesson they should begin interpreting the components in different places. The water
cycle is complex but so very important to our lives.
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Surface movement includes rivers, streams,
creeks, lakes, ponds, and human-made “flood”
control. All surface water is trying to reach sea
level due to gravity. As water flows in channels,
the streambed and banks of the channel will
resist the flow of water. The velocity of the water
is dependant on steepness of the slope, type of
rock or soil, amount of vegetation, shape of stream
bed, and obstructions. Surface water provides the
liquid where most evaporation takes place.
Groundwater refers to water that has
penetrated the soil or bedrock and moves through rocks that have a high pore space. The
water comes from infiltration of surface waters
including lakes, rivers, recharge ponds, and even
waste-water treatment systems. Groundwater is
also affected by the force of gravity. However,
because of some of the properties of water, it can
pool in higher area and actually defy gravity in
some cases. The water stable is the upper level
of the saturated zone of groundwater.
Rivers, streams and creeks
are a surface water system with a
network of channels that collect and
move runoff. Runoff is excess
water that is not adsorbed by the
surrounding area. Runoff can be
created by rainfall, melting snow, or
groundwater discharge. The shape
of the river system will depend on
the topography, the type of rock or
soil it is traveling through, and the
style of its biological diversity. For
instance, pine trees require a lot of
water to grow. Runoff in a pine tree
forest would be less than if the area
was populated by oak trees. Oak
trees require less water than pine, so more water would be available as runoff.
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Perennial stream
Rivers and streams change depending on the amount of
water that flows throughout the year. This relies on a continuous
source of water is from the surface or subsurface. A perennial
flow is a channel that has water all year
round. An example would be the great
rivers of the world including the Ganges
River (India), Amazon River (South
America), or the Nile River (Africa). An
intermittent stream would be a flow that
is more than 50% during the year. An
ephemeral flow generally refers to a
stream or creek that only has water part of
the year. This is usually in areas, like
deserts, that are dry most of the year, but
do have maybe 2 months of rain.
Dry or ephermeral creek
Surface flows will wiggle and wind through the
surface landforms. There are many flow types depending
on the velocity of the river. If the velocity is high, it tends to
cut into bedrock in a “straight” line. Velocities will be high
if there is sufficient relief. When the velocity is low, the
stream will tend to meander if the rock type and topography
permit it.
Water velocity helps to create three basic types of
channel patterns, including braided, meandering, and
straight. There are many patterns that grade into each
other. Rivers in a straight pattern do not stay ruler straight
Braided streams
for long! The physical properties of water and the area the
river is eroding tend to have the deepest part of the river (called the thalweg) alternating
from side to side on the channel. Erosion of the
land starts a physical separation of the pieces.
Larger pieces don’t move very far and drop out of
the system. However, finer grained sediment
settles out in quieter area. So water will be
attacking one side of the river and the other side will
be depositing sediment. Over the years this will
create meandering.
In many areas where you find braided
channels, surface water is just “dumped” into a
lower topographic area. The sediment load is large
and the river gets confused and breaks up into
smaller channels with a branching, but braided look.
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The flow will also dictate how the sediment is deposited,
which in turn contributes to the type of habitat available to
different types of organisms. Three types of bedforms provide
excellent “living” space, including mud, riffles, and pools. The
accumulation of fine-grained sediments (mud) in quiet rivers can
influence growth for small invertebrates and fish eggs. The mud
represents a “cushion”, and if disturbed because of increased
movement of water, can cause damage to the organisms that
live there.
Riffles are relatively shallow portions of a river with a
change in elevation where water cascades over cobbles or
boulders along its path. The fast-moving water allows gas in
the atmosphere to mix with the water, therefore increasing the
dissolved oxygen that enters the water system. Behind the
rocks are areas that debris can build up and act as a habitat for
Riffles
fly larvae and other small invertebrates.
Pools of water are areas that are deeper. When water reaches a pool the velocity
of the water slows down, making it an excellent resting place for fish.
Ground water as it moves
through soil and rock is actually being
naturally filtered. Some substances
like sand can help filter pollutants and
particles easily. Clays in soil and
rock also act as a way to “capture”
and exchange some elements and
compounds when they are dissolved
in water. This helps to eliminate other
pollutants that filtration cannot
handle.
Water is stored in aquifers,
which have similar characteristics of
reservoir rocks that store soil and
gas. Well-sorted sediments with high porosity (A) and highly fractured (C) rocks are
excellent candidates for aquifers. If poorly sorted rocks are partially cemented (B), they
are not good reservoir rocks. The fluid must have room to move around. An aquifer is not
an underground river, it just retains the water until it is pumped out through a well or
naturally emerges as a spring.
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EARTH SCIENCES - WATER
Lesson 5 - Watersheds
MATERIALS:
reader
Internet
Objective: Students use the internet to
find their watershed.
Teacher note
Watersheds refer to how water moves through a defined topographic area.
A more detailed definition would include a geographic area in which all sources of
water, including lakes, rivers, estuaries, wetlands, and streams, as well as ground
water, drain to a common surface water body. Watersheds are diverse. You can
have a desert watershed, flatland watersheds, mountainous watersheds, as well as
coastal watersheds.
In the United States watersheds are delineated by U.S. Geological Survey
using a nationwide system based on surface hydrologic features. This system
divides the country into 21 regions, 222 subregions, 352 accounting units, and 2,262
cataloguing units.
In this activity students will use the “Surf Your Watershed” website from the
Environmental Protection Agency to locate their watershed. You can extend this
lesson by having them locate other watersheds. This will help students learn how
to use this valuable resource to locate information.
Below are a few websites that might help you get more information on
watersheds.
Know your Watershed (Purdue University)
http://www.ctic.purdue.edu/KYW/glossary/whatisaws.html
Surf Your Watershed (Environmental Protection Agency)
http://www.epa.gov/surf/
Locate your Local Watershed (Environmental Protection Agency)
http://cfpub1.epa.gov/surf/locate/index.cfm
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A watershed or drainage basin refers to a
system controlled by topography which defines how
water will flow. You refer to a watershed by the largest
body of water that the creeks, rivers or streams feed
into. For example, all creeks that flow in the San
Francisco Bay are part of the San Francisco
Watershed.
However, there are many smaller
watersheds within this area depending on flow
patterns. Alameda Creek Watershed would be an
area that drains into Alameda Creek.
When it rains, water will flow into its appropriate
watershed. A ridge or
topographical higher
areas that connects
two waters are called a
divide. In the United
States there is an area
in the Rocky Mountain
called the “continental divide.” This refers to water on the
east of the divide flows into the Atlantic. The water on the
west side flows into the Pacific.
Continental Divide
A watershed has an orderly flow pattern. The pattern is dendritic or branching, as
it flows from the headwaters to a larger body of water. When one stream flows into a
larger stream or river they are called tributaries. The smallest channels in a watershed
with no tributaries are called first order streams. A second order stream is when two first
order streams join. If you look at the stream order diagram, you can see the creation of
a fifth order stream channel. Fifth to sixth order streams are usually larger rivers, while
first and second order are often small, steep, or intermittent.
Dendritic pattern of river formation.
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Stream order formation
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Watersheds are affected by different
physical and climatic differences. Climates
refer to the weather in a region over a long
period of time. Your location will determine the
type of the seasonal input of water.
Temperature of the atmosphere caused by
solar radiation will also control the rate and
nature of the precipitation.
Physical make-up of the area where
water flows will also make a difference. If the
rocks and soil are “soft,” water can erode it
easily. The steeper the topography the greater
Steep banks, rapid erosion
the runoff and erosion. An earthquake can
cause an uplift in an area that can change the
shape and extend of how the water flows. Humans can create a dam or build a large
structure which change the course of a river, which effect an entire area.
The vegetation in watersheds
effects the quality of the water.
Grasses, shrubs, and trees make up
the majority of plant cover. As they
fall and decompose, they add the
organic components to the soil. Trees
are the protectors of the watershed.
The tree litter protects the soil’s
surface as the roots of the tree protect
the soil from erosion. Trees also
provide a canopy that keeps the water
cool so organisms don’t die of thermal
pollution.
The canopy can also
reduce the force of the rain and the
velocity of wind in a watershed.
Plant cover is important to a watershed to prevent the erosion of valuable soil as
water rushes downstream. Plant cover also provides food and protection for many small
organisms.
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The green zone along a stream ecosystem is
called a riparian area and has several unique
properties. Riparian zones have the capacity to buffer
rivers and other waters from runoff from agricultural,
urban, or other areas. Healthy riparian zones can
absorb sediments, chemical nutrients, and other
substances contained in runoff.
Riparian areas provide all the components
needed for a wildlife habitat including food, water, and
cover. Diversity of organisms living in these wetland
areas is very high. A riparian habitat includes three
areas depending on the influence of water. The aquatic
area refers to the area that is the stream channel or
pond. The organisms that live in this area must be
adapted to a wet lifestyle. Not far from the banks of the
water is an area referred to as the riparian area which
are organisms that require a moist habitat. Many plants
require their roots to be moist. A transition area
between a riparian area and upland cover is called an
area of influence. Moisture decreases as you move
away from the water.
Riparian vegetation adds to the
shade of an area which helps to
control temperature
and
photosynthesis of plants living in the
stream. It also is a source of larger
and fine plant detritus which is used
by many insects and invertebrates for
their food source. If you have a
vigorous riparian zone, you will have
a diverse flora and fauna living in this
area.
Watersheds naturally clean
themselves as water can be filtered
as it flows in the system. However, we
sometimes pollute these watersheds through industrial or municipal waste discharging into
the watershed (point source pollution). This overloads the systems and pollution
increases. Even non point source pollution (many contributors to pollution) can
accumulate and cause as much damage.
Our watersheds reflect the health of our
environment. Water that migrates through the different levels of the watershed nourishes
biological life. In this activity you are to search the internet and find out more about the
watershed that you live in. Use the worksheet to help find this information.
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EARTH SCIENCES - WATER
PROBLEM: How can you locate more information about your local watershed?
HYPOTHESIS:
MATERIALS: Internet
PROCEDURE: Use the Environmental Protection Agency (EPA) website to find
information about your local watershed (http: //www.epa.gov/surf/). Answer the questions
below and then print out a map of the completed assignment.
1. Name of watershed
2. USGS cataloging unit number
3. State and Counties covered by map:
4. Look at the Environmapper for watersheds. Click on the different mapping features that
you want to locate. Then click on the map and these symbols will appear on the map.
List the symbols you have chosen.
5. Print out a map as instructed by your teacher.
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Earth Science- Water - Unit Test
Part 1. Definitions Match the number of the term or concept in Column 1 with the letter
of the correct definition in Column 2.
Column 1
Column 2
1. riparian
a. resistance between layers
2. watershed
b. excess water that flows after a rainstorm
3. aquifer
c. larger, quieter area in a stream
4. viscosity
d. a river channel that has a “s” shape
5. runoff
e. requirement of many organisms in water
6. pool
f. green zone
7. ephermeral
g. channel that has water all year
8. perennial
h. dry part of the year
9. dissolved oxygen
i. drainage basin
10. meandering
j. underground storage of water
Part 2. Multiple Choice Choose the best answer to complete each statement.
1. Water can be found
a. only on th Earth’s surface
b. inside the Earth only
c. on the surface and subsurface of the Earth
d. none of these
2. Which of the following is not a classification of a stream channel?
a. meander
b. flow
c. braided
d. straight
3. Dissolved oxygen enters water through
a. waterfalls
b. soil
c. rocks
d. humans
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4. Ice floats because
a. it is denser than water
b. water is denser than ice
c. it is cold
d. the molecules are far apart
5. Abundant water in the U.S. is not caused by
a. reservoirs
b. sewage treatment
c. dams
d. beavers
6. Water is
a. a semiliquid
b. a universal solvent
c. a normal component
d. non-renewable resource
7. Which of the following chemical parameters does not affect organisms?
a. hardness of water
b. pH
c. dissolved oxygen
d. viscosity
8. Which of the following is not considered a division of a riparian area?
a. braided
b. area of influence
c. riparian
d. aquatic
9. Riparian canopy vegetation helps to control
a. pH
b. amount of water
c. temperature
d. salinity
10. What is it called when one stream flows into another?
a. steep
b. intermittent
c. divide
d. tributary
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ANSWERS:
Part 1.
1. F
2. I
3. J
4. A
5. B
6. C
7. H
8. G
9. E
10.D
Part 2.
1. C
2. B
3. A
4. B
5. D
6. B
7. A
8. A
9. C
10. D
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