Download THE WATER CYCLE I. Location of Water resources: 97.2% ocean

THE WATER CYCLE
I. Location of Water resources:
97.2% ocean, 2.15% permanently frozen, rest (0.65%) is
groundwater, lakes, streams, air
II. Water transformation
Liquification: change from solid to liquid state
Evaporation: change from liquid to gaseous state
Transpiration: evaporation which occurs through plants
(important in vegetated areas; ususally combined with
evaporation to make evapotranspiration)
Sublimation: change from solid to gaseous state
Condensation: change from gaseous to liquid state
Solidification: change from liquid to solid state
III. Latent heat of water.
Heat is required to make ice become water, and water
become steam (water vapor).. Depending upon the energy
level, water at the freezing point (32 F) can be solid or liquid,
or at the boiling point (212 F) can be liquid or gaseous. Thus,
extra heat is required to melt ice, or to boil water.
Latent heat of Fusion (solid-liquid) = 79.7 calories/g
Latent heat of Vaporization (liquid-gas) = 540 calories/g
This is reason why sweating will help cool body, as water on
skin surface will absorb 540 cal/g of water evaporated
Conversely, when water vapor condenses, 540 calories is
released; and when water freezes, 79.7 calories is released
per gram of water
This released energy is what creates winds, storms, lighting,
etc.
IV. Cloud Formation
Water will transform from gaseous to liquid state when the
air is fully saturated, in other words whrn the relative
humidity = 100%
Saturation concentration of water vapor in air varies with air
temperature, so that cold air can hold much less water vapor
than warm air
Creating saturation can occur in a number of ways:
First, by increasing the amount of water vapor in the air.
However, this requires movements of air masses, and will
take hours to days to happen.
Second, by keeping water vapor levels constant, but
changing the temperature. Warm air which is not saturated
will become so if the temperature falls. This happens when
air rises.
The three major ways in which this can occur are:
(1) convection (fair weather summer clouds)
(2) frontal boundaries (cold front, warm front)
(3) orographic lifting (air moving up a mountain
slope)
This last method is responsible for the formation of rain
shadows in mountainous regions. When moist air is pushed
up a mountain by prevailing winds, the air cools, relative
humidity reaches 100%, and clouds form. These clouds
create rain, which takes water out of the atmosphere. As air
decends the downwind side of the mountain, the temperature
of this water-depleted increases. Relative humidity falls to
much less than saturation, clouds disappear, and rain fall
decreases. At the latitude of the US and Europe, prevailing
winds are from the west. Thus, rainshadows are more
pronounced on the eastern sides of mountains. However, at
more southerly latitudes (Mexico, for instance), prevailing
winds are from the east, creating rain shadows on the
western side of mountains.
V. Groundwater resources.
When rainfall exceeds evapotranspiration, some of the
excess water is drawn by gravity into the ground.
Approximately 95% of the liquid water on land occurs as
groundwater.
Zone of aeration = region in soil horizon in which air is found
in spaces between particles
Zone of saturation = region in soil horizon in which all of
spaces between particles are filled with water
Water table = the line which separates the zones of aeration
and saturation
Aquifer = layer of sediment or rock that is permiable and
transmits water
An artesian well is formed when an aquifer is sandwiched
between inpermiable layers, allowing pressure to develop on
water in an aquifer
Points of discharge occur when groundwater or aquifers
intersect the ground surface
Rates of groundwater flow are quite low (50 feet per year). As
such, it is possible to remove groundwater more rapidly than
it can be replaced. This can cause nearby shallow wells or
springs to run dry.