Transcript Water Resources

Mrs. Ashley
Water as a Resource
 Earth’s surface – 70% water
 97% of water in oceans: salt water
 3% is fresh water
 25% of fresh water is groundwater
 75% of fresh water is in ice and glaciers
 Only .03% of water is available to us: in atmosphere,
streams, rivers, wetlands, lakes
 (Some is lost to pollution)
Properties of Water
 Polar Covalent Bond (sharing of electrons)
 Polarized due to – side and + side
 Water Molecules become bonded weakly with positive to
negative sides of different water molecules (hydrogen
bonds)
 High Specific heat
 Specific heat is the amount of heat energy it takes to raise
or lower the temperature of 1 gram of a substance by
1°Celsius
 Moderates temperatures on Earth
 Stores tremendous quantities of heat energy with small rise
in temperature
Properties of Water
High Specific Heat Energy
 Water has the highest latent heat of vaporization which
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means that water going from liquid to gas requires a lot of
energy
Energy released or absorbed in transforming states is latent
heat
Large quantities of heat energy required to change states
Waters warm slowly in spring, cool slowly in fall
The high specific heat of water, coupled with the amount of
heat absorbed or released in changing its physical state,
combined with the vast quantities of water on the planet,
means that water plays a major role in climate and weather
Properties of Water
 Known as a
universal solvent
(substance
dissolved is called
solute)
 Pure water
becomes denser as
cooled until 4
degrees Celsius and
then becomes less
dense
 Causes ice to float
Properties of Water
 pH of pure water is neutral (7)
 Has high surface tension (water molecules are more
attracted to each other than the air to water)-cohesion is
where hydrogen bonds of water tend to keep molecules
sticking together
 Allows water spiders and
water striders to walk on
water
 Slows down mayflies
and caddisflies when they
try to emerge from water
Adaptation of Mayfly Larvae
 The interplay of hydrophobic and hydrophilic surfaces with water can
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perhaps best be seen by examining mayflies.
These organisms have aquatic larvae with hydrophilic surfaces. These
surfaces allow the larva to exchange gasses (O2, CO2) with the
surrounding water, which can come very close to the hydrophilic skin.
At maturity, the larval mayfly molts to the winged subimago, the stage
that must break through the water's surface. The subimago is covered
with small waxy hairs and beads that are hydrophobic. The subimago
floats to the surface and is literally pushed out of the water as the polar
water molecules attempt to reform behind the subimago.
The subimago can float comfortably on the surface of the water for
several seconds - long enough to provide a target for trout, and the
basis for fly-fishing - before taking off.
It will fly to streamside vegetation and molt again; it is the only insect
to molt once it has reached the winged stage. This second molt gets rid
of the awkward, heavy, waxy coat of the subimago.
Properties of Water
 Viscosity is the force necessary to separate the
molecules and allow an object to pass through
 Water’s frictional resistance is 100 times greater than air
 Organisms in water need a streamlined body to pass
through the water
Properties of Water
 Adhesion: Water adheres to and climbs up materials
like glass
 The qualities of adhesion and cohesion are what allows
water to rise up inside of the tall xylem tubes. This is
capillarity. The narrower tubes the more capillarity
Properties of Water
•The heating and
cooling of the water
also changes its
density
•High water density
allows sound to move
through it over long
distances (important
for whales)
Water and Oxygen
 21 % of air is oxygen
 Only 1% of water is oxygen
 More oxygen tends to be at surface of water
 Wind action
 Photosynthesis
 Waves
 Benthic organisms tend to use up oxygen (BOD)
Applications to Environmental Science
 Most organisms have bodies that are at least 75-90% water, which
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means that at least 90% of their body weight will be offset by the
weight of the water around them.
Benthic organisms usually deal with staying on the bottom by
making that last 10% of the body as dense as possible; they may
have heavy shells, massive bones, or even construct cases out of
rocks to carry around
Swimming organisms (nekton), or floating organisms (plankton),
have the opposite problem. They make the remaining 10% of their
bodies as light as possible. Fats and oils are two biological
molecules that are less dense than water and allow some
organisms to float.
Sharks have large, oil-filled livers which help them float
Trapped air is also effective in helping to float
Waterfowl float high in the water due to air trapped in their
feathers and the hollow bones in their skeletons
Oceans
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Divisions based on:
1. Light penetration: Photic Zone, Aphotic Zone
2. Distance from shore and depth: Neritic Zone,
Oceanic Zone
3. Open water or bottom: Benthic Zone, Pelagic Zone,
Abyssal Zone
4. Intertidal
5. Continental shelf
6. Hydrothermal vent
Oceans
Salinity measured in psu
Acidity in Oceans
 Carbon dioxide in water
 Forms Carbonic Acid H2CO3
H2O +CO2
 H2CO3
H + CO3 Hydrogen and Carbonate
 Below a pH of 4.5 organisms cannot grow and
reproduce
Ocean Currents
 Winds drive currents
 Higher temperature less dense so floats on top
 Thermocline-layer where temperature changes rapidly
 Thermal stratification is permanent in tropics
 Temperate regions stratification is only in summer and
fall has turn over which results in nutrient mixing
Ocean Currents
Ocean Currents
 Gyres
 Move right in northern hemisphere and left in southern
hemisphere
 Surface and deep water currents
 Upwelling on western side of continents and Anartica
Lake Zonation
 Divisions based on:
1. Light penetration: Photic zone, Aphotic zone
2. Distance from shore and depth: Littoral Zone,
Limnetic Zone
3. Open water or bottom: Benthic Zone, Pelagic Zone
Lake Zonation