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

Salt waterGround water

Ice sheets

Surface waterRivers

Lakes

Swamps

World water Fresh watwer Fresh surface watewr

Antarctic Peninsula in 'dramatic' ice lossBy 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 atmosphereAs 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 one-fourth – 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 excess- a

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 every-increasing 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. studyBy Matthew Knight, CNN

November 20, 2012 -- Updated 1655 GMT (0055 HKT)