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The Earth's water is always in movement, and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Water is a common Chemical substance that is essential for the survival of all known forms of Life. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years. Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of General properties of water vapor Evaporation/sublimation Whenever a water molecule leaves a surface it is said to have evaporated Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go in a hurry, but there is always the same amount of water on the surface of the earth.

Contents

Description

The water cycle.
The water cycle.

The water cycle has no starting or ending point. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Evaporation is the process by which Molecules in a Liquid state (e Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Ice and snow can sublimate directly into water vapor. "Snowfall" redirects here For other uses see Snow (disambiguation or Snowfall (disambiguation. Rising air currents take the vapor up into the atmosphere, along with water from evapotranspiration, which is water transpired from plants and evaporated from the soil. The vapor rises into the air where cooler temperatures cause it to condense into clouds. Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Snowpacks in warmer climates often thaw and melt when spring arrives, and the melted water flows overland as snowmelt. Most precipitation falls back into the oceans or onto land, where, due to gravity, the precipitation flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers. Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers (saturated subsurface rock), which store huge amounts of freshwater for long periods of time. An aquifer is an underground layer of Water -bearing Permeable rock or unconsolidated materials ( Gravel, Sand, Silt, or Clay Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as ground-water discharge, and some ground water finds openings in the land surface and emerges as freshwater springs. Over time, the water continues flowing, some to reenter the ocean, where the water cycle renews itself.

The different processes are as follows:

  • Precipitation is condensed water vapor that falls to the Earth's surface. In Meteorology, precipitation (also known as one class of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet. Rain is Liquid precipitation. On Earth it is the condensation of atmospheric Water vapor into drops heavy enough to fall often making it to "Snowfall" redirects here For other uses see Snow (disambiguation or Snowfall (disambiguation. Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground Graupel (also called snow pellets) refers to precipitation that forms when supercooled Droplets of Water condense on a Snowflake forming [1] Approximately 505,000 km³ of water fall as precipitation each year, 398,000 km³ of it over the oceans. [2]
  • Canopy interception is the precipitation that is intercepted by plant foliage and eventually evaporates back to the atmosphere rather than falling to the ground. Interception, or canopy interception, refers to precipitation that does not reach the soil but is instead intercepted by the leaves and branches of plants
  • Snowmelt refers to the runoff produced by melting snow. In Hydrology, snowmelt is Surface runoff produced from melting Snow.
  • Runoff includes the variety of ways by which water moves across the land. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows This includes both surface runoff and channel runoff. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows Streamflow, or channel runoff, is the flow of Water in Streams Rivers and other channels and is a major element of the Water As it flows, the water may infiltrate into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.
  • Infiltration is the flow of water from the ground surface into the ground. Infiltration is the process by which water on the ground surface enters the Soil. Once infiltrated, the water becomes soil moisture or groundwater. Water content or moisture content is the quantity of Water contained in a material such as Soil (called soil moisture) rock, Groundwater is Water located beneath the Ground surface in Soil pore spaces and in the Fractures of lithologic formations [3]
  • Subsurface Flow is the flow of water underground, in the vadose zone and aquifers. Subsurface flow is the flow of water beneath ground surface in Hydrology. Subsurface water may return to the surface (eg. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at lower elevation than where it infiltrated, under the force of gravity or gravity induced pressures. Gravitation is a natural Phenomenon by which objects with Mass attract one another Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years.
  • Evaporation is the transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere. Evaporation is the process by which Molecules in a Liquid state (e [4] The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Transpiration is the Evaporation of water from the aerial parts of Plants especially leaves but also stems Flowers and Roots Plants are living Organisms belonging to the kingdom Plantae. Evapotranspiration (ET is a term used to describe the sum of Evaporation and Plant Transpiration from the earth's land surface to Atmosphere Total annual evapotranspiration amounts to approximately 505,000 km³ of water, 434,000 km³ of which evaporates from the oceans. [5]
  • Sublimation is the state change directly from solid water (snow or ice) to water vapor. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage [6]
  • Advection is the movement of water — in solid, liquid, or vapour states — through the atmosphere. Advection, in mechanical and chemical engineering is a transport mechanism of a substance or a conserved property with a moving Fluid. Without advection, water that evaporated over the oceans could not precipitate over land. [7]
  • Condensation is the transformation of water vapour to liquid water droplets in the air, producing clouds and fog. Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body Fog is a cloud that is in contact with the ground Stratus clouds are usually the only clouds that touch the ground [8]

Reservoirs

Volume of water stored in
the water cycle's reservoirs[9]
Reservoir Volume of water
(106 km³)		 Percent
of total
Oceans 1370 97. To help compare different Orders of magnitudes this page lists Volumes between 1 million and 1 billion ( thousand million) cubic Kilometres (10^{15} 25
Ice caps & glaciers 29 2. 05
Groundwater 9. 5 0. 68
Lakes 0. 125 0. 01
Soil moisture 0. 065 0. 005
Atmosphere 0. 013 0. 001
Streams & rivers 0. 0017 0. 0001
Biosphere 0. 0006 0. 00004

In the context of the water cycle, a reservoir represents the water contained in different steps within the cycle. A reservoir is most broadly a place or hollow vessel where Fluid is kept in Reserve, for later use The largest reservoir is the collection of oceans, accounting for 97% of the Earth's water. An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. The next largest quantity (2%) is stored in solid form in the ice caps and glaciers. A solid' object is in the States of matter characterized by resistance to Deformation and changes of Volume. An ice cap is an Ice mass that covers less than 50 000 km² of land area (usually covering a highland area "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. The water contained within all living organisms represents the smallest reservoir.

The volume of water in the fresh water reservoirs, particularly those that are available for human use, are important water resources. Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved Water resources are sources of Water that are useful or potentially useful to Humans Uses of water include Agricultural, industrial, Household [10]

Residence times

Average reservoir residence times[9]
Reservoir Average residence time
Oceans 3,200 years
Glaciers 20 to 100 years
Seasonal snow cover 2 to 6 months
Soil moisture 1 to 2 months
Groundwater: shallow 100 to 200 years
Groundwater: deep 10,000 years
Lakes (see lake retention time) 50 to 100 years
Rivers 2 to 6 months
Atmosphere 9 days

The residence time of a reservoir within the hydrologic cycle is the average time a water molecule will spend in that reservoir (see the adjacent table). Lake retention time (also called the Residence time of lake water or the water age or flushing time) is a calculated quantity expressing the Residence time is a broadly useful concept that expresses how fast something moves through a system in equilibrium It is a measure of the average age of the water in that reservoir, though some water will spend much less time than average, and some much more.

Groundwater can spend over 10,000 years beneath Earth's surface before leaving. Particularly old groundwater is called fossil water. Fossil water or paleowater is Groundwater that has remained in an Aquifer for millennia Water stored in the soil remains there very briefly, because it is spread thinly across the Earth, and is readily lost by evaporation, transpiration, stream flow, or groundwater recharge. After evaporating, water remains in the atmosphere for about 9 days before condensing and falling to the Earth as precipitation.

In hydrology, residence times can be estimated in two ways. The more common method relies on the principle of conservation of mass and assumes the amount of water in a given reservoir is roughly constant. The law of conservation of mass/matter, also known as law of mass/matter conservation (or the Lomonosov - Lavoisier law says that the Mass of With this method, residence times are estimated by dividing the volume of the reservoir by the rate by which water either enters or exits the reservoir. Conceptually, this is equivalent to timing how long it would take the reservoir to become filled from empty if no water were to leave (or how long it would take the reservoir to empty from full if no water were to enter).

An alternative method to estimate residence times, gaining in popularity particularly for dating groundwater, is the use of isotopic techniques. This is done in the subfield of isotope hydrology. Isotope hydrology is a field of Hydrology that uses isotopic dating to estimate the age and origins of Water and of movement within the Hydrologic

Changes over time

The water cycle describes the processes that drive the movement of water throughout the hydrosphere. A hydrosphere (from Greek ύδωρ - hydor, " Water " + σφαίρα - sphaira, " Sphere " However, much more water is "in storage" for long periods of time than is actually moving through the cycle. The storehouses for the vast majority of all water on Earth are the oceans. It is estimated that of the 332,500,000 cubic miles (mi3) (1,386,000,000 km3) of the world's water supply, about 321,000,000 mi3 (1,338,000,000 km3) is stored in oceans,or about 95%. It is also estimated that the oceans supply about 90 percent of the evaporated water that goes into the water cycle. [11]

During colder climatic periods more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age glaciers covered almost one-third of Earth's land mass, with the result being that the oceans were about 400 feet (122 meters) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 18 feet (5. 5. meters) higher than they are now. About three million years ago the oceans could have been up to 165 feet (50 meters) higher. [11]

The scientific consensus expressed in the 2007 Intergovernmental Panel on Climate Change (IPCC) Summary for Policymakers[12] is for the water cycle to continue to intensify throughout the 21st century, though this does not mean that precipitation will increase in all regions. In subtropical land areas — places that are already relatively dry — precipitation is projected to decrease during the 21st century, increasing the probability of drought. A drought is an extended period of months or years when a region notes a deficiency in its water supply The drying is projected to be strongest near the poleward margins of the subtropics (for example, the Mediterranean Basin, South Africa, southern Australia, and the Southwestern United States). The subtropics are the zones of the Earth immediately north and south of the tropic zone which is bounded by the Tropic of Cancer and the Tropic of The Mediterranean Basin refers to the lands around and surrounded by the Mediterranean Sea. The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa For a topic outline on this subject see List of basic Australia topics. The Southwestern area of the United States could be defined as the states west of the Mississippi River, with the qualification of a certain northern limit such as the 37 Annual precipitation amounts are expected to increase in near-equatorial regions that tend to be wet in the present climate, and also at high latitudes. These large-scale patterns are present in nearly all of the climate model simulations conducted at several international research centers as part of the 4th Assessment of the IPCC. This article is about the theories and mathematics of climate modeling

Glacial retreat is also an example of a changing water cycle, where the supply of water to glaciers from precipitation cannot keep up with the loss of water from melting and sublimation. Glacial retreat since 1850 has been extensive. whitechuck glacier 2006jpg|right|thumb|320px|The same view as seen in 2006 where this branch of glacier retreated 1 [13]

Human activities that alter the water cycle include:

Effects on climate

The water cycle is powered from solar energy. Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture A dam is a barrier that divides waters. Dams generally serve the primary purpose of retaining water while other structures such as Floodgates, Levees Deforestation is the conversion of Forested areas to non-forest land for use such as Arable land, Pasture, urban use logged area or wasteland Afforestation is the process of establishing a forest on land that is not a forest or has not been a forest for a long time by planting trees or their seeds Water abstraction, or water extraction, is the process of taking Water from any source either temporarily or permanently Urbanizationn (also spelled urbanisation) is the physical growth of Urban areas into rural or natural land as a result of population in-migration to an existing 86% of the global evaporation occurs from the oceans, reducing their temperature by evaporative cooling. Evaporative coolers (also called swamp, desert, or air coolers) are devices that cool air through the simple Evaporation of water Without the cooling effect of evaporation the greenhouse effect would lead to a much higher surface temperature of 67 °C, and a warmer planet. The Celsius Temperature scale was previously known as the centigrade scale. [14]

Effects on biogeochemical cycling

While the water cycle is itself a biogeochemical cycle,[15] flow of water over and beneath the Earth is a key component of the cycling of other biogeochemicals. In Ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a Chemical element or Molecule moves through both biotic Runoff is responsible for almost all of the transport of eroded sediment and phosphorus[16] from land to waterbodies. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Phosphorus, (ˈfɒsfərəs is the Chemical element that has the symbol P and Atomic number 15 A body of water is any significant accumulation of Water, usually covering the Earth or another planet The salinity of the oceans is derived from erosion and transport of dissolved salts from the land. Salinity is the Saltiness or dissolved salt content of a body of Water. Cultural eutrophication of lakes is primarily due to phosphorus, applied in excess to agricultural fields in fertilizers, and then transported overland and down rivers. Eutrophication is an increase in chemical Nutrients -- typically compounds containing Nitrogen or Phosphorus -- in an Ecosystem, and may occur In Agriculture, a field refers generally to an area of Land enclosed or otherwise and used for agricultural purposes such as Cultivating crops Fertilizers ( also spelt fertiliser are chemical compounds given to Plants to promote growth they are usually applied either through the soil for uptake by plant Both runoff and groundwater flow play significant roles in transporting nitrogen from the land to waterbodies. [17] The dead zone at the outlet of the Mississippi River is a consequence of nitrates from fertilizer being carried off agricultural fields and funnelled down the river system to the Gulf of Mexico. This page is about the oceanic phenomenon see Dead Zone for other uses The Mississippi River is the second longest River in the United States, with a length of from its source in Lake Itasca in Minnesota to In Inorganic chemistry, a nitrate is a salt of Nitric acid with an Ion composed of one Nitrogen and three Oxygen atoms The Gulf of Mexico ( Spanish: Golfo de México) is the ninth largest Body of water in the world Runoff also plays a part in the carbon cycle, again through the transport of eroded rock and soil. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the Biosphere, Pedosphere, Geosphere, Hydrosphere, and [18]

See also

References

  1. ^ Arctic Climatology and Meteorology. A flood is an overflow of an expanse of water that submerges land a deluge A drought is an extended period of months or years when a region notes a deficiency in its water supply Precipitation. Retrieved on 2006-10-24.
  2. ^ Dr. Art's Guide to Planet Earth. The Water Cycle. Retrieved on 2006-10-24.
  3. ^ National Weather Service Northwest River Forecast Center. Hydrologic Cycle. Retrieved on 2006-10-24.
  4. ^ Arctic Climatology and Meteorology. Evaporation. Retrieved on 2006-10-24.
  5. ^ Dr. Art's Guide to Planet Earth. The Water Cycle. Retrieved on 2006-10-24.
  6. ^ Arctic Climatology and Meteorology. Sublimation. Retrieved on 2006-10-24.
  7. ^ Arctic Climatology and Meteorology. Advection. Retrieved on 2006-10-24.
  8. ^ Arctic Climatology and Meteorology. Condensation. Retrieved on 2006-10-24.
  9. ^ a b PhysicalGeography. net. CHAPTER 8: Introduction to the Hydrosphere. Retrieved on 2006-10-24.
  10. ^ Environmental Literacy Council. Water Cycle. Retrieved on 2006-10-24.
  11. ^ a b http://ga.water.usgs.gov/edu/watercycleoceans.html USGS, The Water Cycle: Water Storage in Oceans - Retrieved on 2008-05-14
  12. ^ Intergovernmental Panel on Climate Change. Climate Change 2007: The Physical Science Basis, WG1 Summary for Policymakers
  13. ^ U. S. Geologic Survey. GLACIER RETREAT IN GLACIER NATIONAL PARK, MONTANA. Retrieved on 2006-10-24.
  14. ^ Science at NASA. NASA Oceanography: The Water Cycle. Retrieved on 2006-10-24.
  15. ^ The Environmental Literacy Council. Biogeochemical Cycles. Retrieved on 2006-10-24.
  16. ^ The Environmental Literacy Council. Phosphorus Cycle. Retrieved on 2006-10-24.
  17. ^ Ohio State University Extension Fact Sheet. Nitrogen and the Hydrologic Cycle. Retrieved on 2006-10-24.
  18. ^ NASA's Earth Observatory. The Carbon Cycle. Retrieved on 2006-10-24.

External links

Biogeochemical cycles
Carbon cycle - Hydrogen cycle - Nitrogen cycle
Oxygen cycle - Phosphorus cycle - Sulfur cycle - Water cycle

The National Oceanic and Atmospheric Administration ( NOAA) is a scientific agency within the United States Department of Commerce focused on the conditions of the The Geophysical Fluid Dynamics Laboratory (GFDL is a laboratory in the National Oceanic and Atmospheric Administration (NOAA/ Office of Oceanic and Atmospheric Research In Ecology and Earth science, a biogeochemical cycle is a circuit or pathway by which a Chemical element or Molecule moves through both biotic The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the Biosphere, Pedosphere, Geosphere, Hydrosphere, and Hydrogen is one of the constituents of Water. It recycles as in other Biogeochemical cycles It is actively involved with the other cycles like The nitrogen cycle is the Biogeochemical cycle that describes the transformations of Nitrogen and nitrogen-containing compounds in nature The oxygen cycle is the Biogeochemical cycle that describes the movement of Oxygen within and between its three main reservoirs the atmosphere (air the The phosphorus cycle is the Biogeochemical cycle that describes the movement of Phosphorus through the Lithosphere, Hydrosphere, and Biosphere Sulfur is one of the constituents of many Proteins Vitamins and Hormones It recycles as in other Biogeochemical cycles The essential

Dictionary

water cycle

-noun

  1. The natural cycle of evaporation of water from the oceans etc, and subsequent condensation and precipitation as rain and snow
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