The Water Cycle
• 1.One of the earth´s great cycles is the water
cycle (hydrological cycle).
• Water constantly moves from the atmosphere
to the earth to the oceans and then back to
the atmosphere. As it moves, water changes
the surface of the earth.
• Because it is a universal sovent, it is critical to
the existance of life.
• Water is a powerful agent of geological
(geomorphological and gtochemical) change.
• Erosion is primarily washing away of some
portion of the global crust by running water.
• While flowing over the land, water fashions
buttes, canions, and mesas.
• It also transports and deposits nutrients and
sediments )e.g., 2 million tons of sediments are
deposited each day at the mouth of Mississipi
River).
• But this brief residence on land is only one link in the
water cycle.
• Water is not simply distributed among the oceans,
fresh and ground water on the land, and water vapor in
the atmosphere – rather it is constantly being cycled
from one of these locations to another.
• This water cycle is driven by energy from the sun and
by gravity, and it provides the connection among the
atmosphere, the litosphere, and the hydrosphere that
makes the presence opf life on earth possible.
• Life and water are inseparable. Most living tissue
is composed of water, which acts as the medium
for the chemical reactions within the body cells.
• Being a universal solvent – almost any substance
will dissolve in it – water carries most of life´s
essential nutrients.
• Plants, for example, obtain all of their mineral
nutrients by soil water intake in which the
necessary substances are dissolved.
• In the human body, vital water-soluble
nutrients (mineral salts, vitaminsm,
carbohydrates, etc.) are carried through the
watery media of blood, digtstive juices, and
lymph.
• Wastes are exported from the body dissolved
in the fluids of urine and perspiration.
• 2. Water moves from the atmosphere, where
it exists as water vapor, to the earth´s surface,
where it is used by organisms, and back again
to the atmosphere.
• It has been estimated that the total volume of
water in the biosphere would amount
to 359 x 1015 gallons. (1357x 1015 l)
• About 97 % of the total volume is saltwater in the
oceans and seas.
• About 2.25 % is frozen in polar ice caps and
glaciers.
• Most of the remaining 0.75 % is found in
freshwater lakes, ground water, and other surface
water (rivers, etc.).
Water distribution on earth
Fresh water
Surface water
Ground water
Salt water
Rivers
Swamps
Lakes
Ice sheets
World water
Fresh watwer
Fresh surface watewr
Antarctic Peninsula in 'dramatic' ice loss
By Jonathan Amos BBC Science Correspondent
Растущую трещину в антарктическом леднике Пайн-Айленд ученые обнаружили
в октябре 2011 года. Тогда мало кто предполагал, что огромное ледяное плато полностью
отделится от ледника только спустя два года. На площади нового плавучего «острова»,
которая оценивается в 720 квадратных километров, вполне может разместиться Москва.
© Dmytro Pylypenko | Shutterstock.com
• A surprisingly small amount of water exists in
the atmosphere as water vapor
(about 0.001 %).
•
Africa's biggest and oldest trees, baobabs, are found in South Africa's driest
regions. In Modjadjiskloof, the tree that locals claim is the largest baobab in the
world (not pictured) stands at 22 meters high and 47 meters in diameter. The
center is hollow and has been turned into a bar.
Figure shows:
Evaporation: the sun’s energy causes water
to evaporate and to rise into the atmosphere
As water vapor. Most evaporation occurs over
The cycle’s greatest reservoir, the ocean. A
smaller
proportions of evaporation takes place over
land
water such as lakes and rivers.
Transpiration: water stored in plant tissues
Through the plant membrane and enters
the atmosphere as water vapor. An acre of
corn
transpires up to 400, 000 gallons in a single
growing season
• We have seen that air currentscan transpoirt
substances for thousands of miles. Water vapor in
the atmosphere is also carried great distances.
• When the warm air carrying the vapor cools, the
vapor condenses into liquid water. We see this
condensation as clouds.
• As the condensation continues, not all of the
vapor condenses , however. Of the water vapor
passing over the continents in the course of a
year, only about 10% falls as precipitation.
The world's oceans are becoming acidic at an "unprecedented rate"
and may be souring more rapidly than at any time in the past 300
million years.
• Precipitation over the ocean is more than three times greater that over
land.
• Water precipitation may take any of several courses:
• It may be immediately reevaporated by the sun’s energy.
This is called simultaneous evaporation.
• It may fall into the major water reservoir, the ocean.
• It may fall onto land masses, which results in one of the following: it may
infiltrate the soil to be absorbed by plant roots, used in photosynthesis,
and transpired.
• It may run off to join streams and rivers, and eventually reach the ocean. It
is this water that is primarily responsible for eroding the earth’s surface.
• It may sink downward to join ground water reservoirs and then reappear
later as springs, seeps, or lakes.
• It may be evaporated once again.
• The use of water by land life depends upon how
long the water stays on the land before it reaches
the ocean. The longer water stays on land the
more likely it is that it will be used.
• Surface and ground water provide man’s
freshwater supply.
• Vegetation also takes up significant amounts of
water, thus prolonging the time water spends on
land. But some of man’s cities and highways tend
to hastenwater’s return to the ocean, since water
cannot penetrate paved surfaces.
• 3 . The distribution of precipitation depends
upon the land’s surface features (landscape,
topography), as well as upon prevailing
atmospheric conditions.
The effect of topography
The sheltered side of the mountain range receive less precipitation than
Its windward side. When moist air hits a mountain range, it depleted air
crosses the peak of the range, it descendens and becomes warm. It picks up
moisture evaporated from land surfaces and releases it beyond the sheltered
side of the range.
Grand Canyon, Arizona
•
Utah's Bryce Canyon (pictured) is the closest you can get to another planet without tickets on Virgin Galactic. Then there's
Black Canyon of the Gunnison (Colorado), Palo Duro Canyon (Texas), Canyon de Chelly (Arizona), Sequioa and Kings Canyon
(California), Waimea Canyon (Hawaii) and hundreds more to round out a list so deep and wide that it makes the U.S. the
hands-down winner in this category even without mentioning the Grandest one of them all.
• 4. Evaporation is directly proportional to
temperature.
• The higher the temperature the greater the
evaporation and consequently the less water
available for the land.
• In some very hot areas, precipitation and
evaporation occur simultaneously, and no
water ever reaches the ground.
A new global monitoring system has been launched that
promises "near real time" information on deforestation
around the world.
• In Northern Australia, for example, rainfall
occurs mainly in the summer whwn it is very
hot. In this cast the raifall does not mean a
good growing season, because the rainwater
wvaporates so rapidly and completely that
none is left for use by plants.
Austraalia
• Ecologists measure wheather or not water is
effectively avaiable for living things by
studying the ratio of precipitation to
evaporation. This ratio, and not simply the
amount of rainfall, determines if a land area
will have water available for the growth of
living things.
Relationship between raifall and evaporation
(after Thornthwaite, 1955
)
• Figure shows the relationship between rainfall and
evaporation in the three areas.
• The dotted areas in the charts (water deficiency)
indicates the season when water may be a limiting
factor.
• Periods of water deficiency are only partly determined
by the amount of rainfall. Rain falling during periods of
high evaporation is virtually unavailable to living
organisms.
• Evaporation is directly proportional to temperature,
the higher the temperature the greater the
evaporation.
• 5. Technological man and his activities require
enormous amounts of water, not just for
drinking, washing, and flushing toilets (five
gallons each time), but also for producing
food, fibers, and all our modern conveniences.
• We have become so accustomed to running to
the tap’for water and to the store for our
goods that it is easy to forget that we are all
drawing on the same limited supply of
resources.
• The water availability to man is almost
exclusively confined to water that has reached
the land and is on its way to the sea.
• The North America receives approximately
4,300 billion gallons of rainwater fall a day.
• Of this total, 3,000 billion gallons evaporate
directly from the soil’or are transpired by
plants,. The remainder (a little more than onefourth – 1,300 billion gallons) runs off in rivers
and streams or become ground water.
• A major entry, often overlooked in man’s
water bydget, is the water used in food
production.
• The amount of water passing through crops
(used for both food and feed) and transpiring
back to the atmosphere must be considered
consumption because it is not again available
until it is brought back to land by
precipitation.
• Accounting for this transpiration brings man’s
water budget to staggering heights.
• The average european daily food water
budget is about 3,500 gallons (13230 l).
• The water costs of some common foods,
which will give us an idea of this heavy
taxation made on the water cycle:
•
•
•
•
•
•
An orange – 90 – 110 gallons (340-415 l)
An egg – 120-150 gallons (420-525 l)
A 16-ounce loaf of bread – 300 gallons (1134 l)
A quart of milk – 1,000 gallons (3780 l)
A 1 kg of beef – 24500 l.
The figures include the water needed to make
the feed going into animal production.
• Secondary production – raising animals – is
extremely costly in water terms because the
water must pass first through the plants and
then through the livestock.
• Although the animals themselves consume
some water, and some is used in the dairies,
factories, and farms, the major water use
occurs in raising the crops to be fed to the
livestock.
• Man’s requirements in transpired water
exceed those for food alone because much of
his clothing and home furnishing also come
from living tissue.
• For example: one wool suit carries a “water
price tag” of 225,000 – 250,000 gallons
(850500 -945000 l).
• A cotton suit appeares to be – 10 to 20 times
less.
• This type of analysis can be expanded to include
the water costs of industrial processes.
• For instance, the production of an average-size
car requires 65,000 gallons ( 227500 l) of water.
• If a suit of sythetic fiber is more to your like than
one of wool or cotton, you should count on the
manufacturing process using 1,250 gallons of
water. For every ton of coal used in an electric
power plant, 6000 tons of water are needed.
Nuclear power plants take even more water.
• About 270 billion gallons of water per day are
directly used in the EU, accounting for about
22 % of the total run-off.
• Most of this is reused again and again, as
downstream cities receive upstreame sewage
discharges into their water supppplies.
• Only an estimated 5 % ()61 billion gallons) is
actually consumed per day.
Water crisis
• But what of this talk of water shortage and water
crisis?
• This stems partially from the realities of water
distribution – the people are not where the water
is.
• Another factor contributing to shortages in the
midst of plenty is the effect of our use on water
quality.
• Our use of fresh water often leaves it unsuitable
for reuse without costly treatment.
• Ninety-five percent of our freshwater run-off is used as
conveyor belt carrying domestic and industrial wastes
including heat to the sea.
• Run-off from irrigated and chemically treated
agricultural lands also ends up in that ultimate waste
receptacle.
• In most of our rivers and streams we have now reached
the maximun concentration of wastes that the flowing
water can handle alone.
• The main problem then is not haqving enough water,
but having enough that is fit for various human,
industrial, agricultural, and recreational uses.
• Sediments, foodstuffs, poisons, and heat are constantly and
naturally entering waters. The biotic and abiotic elements
ofv the various water ecosystems can handle certain
amounts of each of these things during certain periods of
time.
• However, if man puts in large amounts of these substances
in a relatively short period of time, the water system is
unable to handle the input and the system is changed and
ulrtimately destroyed.
• Normal amounts of sediments, foodstuffs (detritus matter),
poisons, or heat are not pollution.
• However, if they are introduced at a rate exceeding the
normal rate, then they constirtute pollution.
Pollution
• 6. Pollution is basically a problem of excessa
problem of too much too fast
• Water in natural ecosystems is always receiving certain
amounts of foreign substances, which are diluted or
filtrated out through natural processes.
• When the input becomes so great that natural
processes cannot control it, however, we say that
pollution has occurred.
• A substance is not a pollutant because it is a poison; it
is a pollutant because it is an amount of poison that
the ecosystem can’t naturally handle on a normal
period of time.
Ehkki keemiarelvi Teises maailmasõjas Euroopa pinnal kasutusele ei võetud, toodeti neid ometi
massiliselt. Skagerraki väina Põhjameres uputati 170 000 tonni keemiarelvi – seal lasti põhja
terved keemiarelvi täis tuubitud laevad.
Pärast sõda nuputasid liitlased, mida teha Hitleri Saksamaa keemiarelvadega, ja parimaks
lahenduseks peetigi uputamist. Läänemerre uputati seejärel 50 000 tonni keemiarelvi, milles
leidus 15 000 tonni ohtlikku toimeainet.
Russia
• There was a time when we could say that
flowing water purified itself every temn miles.
• An increasing population with its everyincreasing per capita contribution of wastes
now make this a dream of the past.
• There are four basic types of pollution that
commonly affect the waters of industrial
societies:
• (1) thermal pollution;
• (2) cultural sedimentation;
• (3) poisons;
• (4) cultural eutrophication.
• (1) we have seen that all human activity ultimately
results in the formation of heat which must be
disposed of. When human activity results in an
abnormal increase in the heat in some part of he
environment we refer to this as thermal pollution.
• Industrial processes use tremendous amounts of water
for cooling. Power plants give up waste heat when cool
water from a river , lake, or body of salt water passes
through the steam condenser.
• Heat from the steam is transferred to the cooling
water, which returns to its source some 10-20 F
warmer than when it entered.
• The use of natural waterways for industrial
cooling poses a serious threat to fish and
other organisms.
• Thermal pollution threatens to become an
increasing problem.
• By 2020, the prediction is, that electrical
power plants will be heating up more than
half the water in all the rivers and streams.
• (2) The dumping of solid wastes un water,
beyond natural inputs of solid material, can be
called cultural sedimentation.
• In this category we include non-toxic materials
that accelerate the physical “filling up” of
waterways by settling to the bottom and
remaining there. Such materials include
beverage cans, old tires, nonorganic garbage,
autos, ans sunken ships.
• (3) Most synthetic chemical compounds (about 1
million) produced today are new to the biological
systems.
• They are not readily broken down by living
organisms and may even be poisonous
whenpresent in amounts too large for the system
to effectively dilute and disperse.
• The introduction of poisons into water systems is
obviously a type of pollution. Most pesticides and
many industrial wastes fall into this catwegory.
Eutrophication
• (4) Then there is the case of having too much of a good thing.
Aquatic plants require nutrients such as phosporus, nitrogen, and
carbon in fixed proportions.
• The productivity of aquatic systems is usually limited by the level of
these nutrients, particularly phosphorus and nitrogen, which only
exist in limited supply in natural waters.
• Through a natural growth and aging process called eutrophication ,
aquatic systems acquire more of these nutrients and slowly
“mature”.
• This process naturally occurs over geological time but can be greatly
accelerated by man’s nutrient inputs.
• By introducing large quantities of phosphates and nitrate into water
systems through sewage and run-off, masn tncourages algae
growth.
Rohevetikad Kollases meres
Algae in Barents Sea (NASA)
• Earthobservatory.nasa.gov
Cultural eutrophication
• With this fertilization, the algae flourish, greatly increase in
numbers, die, and bacteria begin the process of quickly use
up the deep-water oxygen that fish, crustaceans, worms,
insrcts and larvae need to live.
• This process can be called
cultural eutrophication.
• Continued breakdown of the sediment produces hydrogen
sulfide gas and other foul-smelling compounds.
• Weeds and other plants clog the waters.
• By simply adding nutrients, man can change a relative clear
lake into a foul-smelling swamplike body of water thick with
algae scums and decaying vegetation.
Ground water
• 7. Because of insufficient usable ru-off, we are now
overusing ground water.
• Ground water – water in the saturated zone beneath
the ground surface – accounts for sixty times more
water than in lakes and streams.
• But a problem arises when the water is withdrawn
faster than the recharge rate (the rate at which water
seeps into the earth from the surface).
• The water table in industrial areas continually dropping
wherever we are drawing on our underground water
capital.
• In addition, as contaminated water infiltrates
into ground water reservoirs, these subsurface
waters also become contaminated.
• Our rate of withdrawal is currently exceeding
twice the recharge rate.
• So ground water levels are receding and water
must be pumped to the surface from ever
greater depths.
Old Faithful, Yellowstone, USA
• Water scarcity will be one of the defining
features of the 21st century.
• The U.N. predicts that by 2025 two thirds of the
world's population will suffer water shortages.
• Find out more at unwater.org.
Greenhouse gases reached record highs in 2011, says U.N. study
By Matthew Knight, CNN
November 20, 2012 -- Updated 1655 GMT (0055 HKT)