excelente la información.
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excelente la información.
It is interesting to the facts.
Really this absolutely more detailed, but I would suggest to Alison to improve page usability because that page is not good by using smart phone or tabs or what so ever, so it is good idea to get an android or iOS apps of this page.
Water is life thanks for this lesson.
As mining activities reduce the amount of fresh water available for human use?
thanks so much.
Can mining activities reduce the amount of water available for human use?
how can i change my rate from red green ?
does evaporation take place at cold areas like the north and south pole?
también es importante considerar que la transpiración de las plantas contribuyen al movimiento de las masas de aire caliente y frío, para dar continuidad al ciclo del agua en la Tierra,
All living organisms require water for their continued existence. The water cycle (hydrologic cycle) is composed of the interconnections between water reservoirs in the environment and living organisms and the physical processes (e.g., evaporation and condensation) involved in its transport between those reservoirs.
The oceans contain about 97% of the total water on the planet, which leaves about three percent as fresh water. Most of the fresh water is locked up in glacial and cap ice or buried deep in the earth where it is economically unfeasible to extract it. One estimate gives the amount of fresh water available for human use to be approximately 0.003% of the total amount of fresh water. However, this is actually a more than adequate supply, as long as the natural cycle of water is not severely disturbed by an outside force such as human activity.
The earth is sometimes known as the \"water planet\" because over 70% of its surface is covered by water. The physical characteristics of water influence the way life on earth exists. These characteristics include:
1. Water is a liquid at room temperature, and remains as such over a relatively wide temperature range (0-100° C). This range overlaps the annual mean temperature of most biological environments.
2. It takes a relatively large amount of energy to raise the temperature of water (i.e., it has a high heat capacity). For this reason, the vast oceans act as a buffer against sudden changes in the average global temperature.
3. Water has a very high heat of vaporization. Water evaporation thus provides a good means for an organism to dissipate unwanted heat.
4. Water is a good solvent for many compounds and provides a good medium for chemical reactions. This includes biologically important compounds and reactions.
5. Liquid water has a very high surface tension, the force holding the liquid surface together. This enables upward transport of water in plants and soil by capillary action.
6. Solid water (ice) has a lower density than liquid water at the surface of the earth. As a result ice floats on the surface of rivers, lakes, and oceans after it forms, leaving liquid water below where fish and other organisms can continue to live. If ice were more dense than liquid water, it would sink, and bodies of water in cold climates might eventually freeze solid.
There are several important processes that affect the transport of water in the water cycle. These include:
Evaporation is the process by which liquid water is converted to water vapor. The source of energy for this process is usually the sun. For example, the sun\'s radiation heats the surface water in a lake causing it to evaporate. The resulting water vapor is thus added to the atmosphere where it can be transported to another location. Two important effects of the evaporation are cooling and drying.
Transpiration is a process by which water evaporates from living plants. Water from the soil is absorbed by a plant\'s roots and transported to the leaves. There, some is lost as vapor to the atmosphere through small surface openings.
When water vapor in the atmosphere cools, it can transform into tiny droplets of liquid water. This process is called condensation, and it can occur as water vapor is transported into the cooler upper atmosphere.
Dust and pollen in the atmosphere help to initiate the process by providing condensation centers. If the droplets remain small enough to be supported by air motions, they can group together to form a cloud. Condensation can also occur in the air near the ground as fog or on plant leaves as dew.
When condensed water droplets grow so large that the air can no longer support them against the pull of gravity, they fall to the earth. This is the process called precipitation.
If the water droplets fall as liquid, it is called rain. If the temperature of the surrounding air mass is cold enough to freeze the water droplets, the resultant precipitation can be called snow, sleet or hail, depending upon its morphology.
Water falling on the ground (e.g., as precipitation or irrigation), can move down-slope over the surface (e.g., surface runoff) or penetrate the surface (e.g., infiltration). The amount of surface runoff and infiltration depends upon several factors: water infall rate, surface moisture, soil or rock texture, type and amount of surface cover (e.g., leaves and rooted plants), and surface topography.
Surface runoff is the predominate process that occurs after precipitation, with most of the water flowing into streams and lakes. On a ground-slope unprotected by vegetation, runoff can occur very rapidly and result in severe erosion.
Water that infiltrates the surface can move slowly downward through the layers of soil or porous rock in a process known as percolation. During this process, the water can dissolve minerals from the rock or soil as it passes through. The water collects in the pores of rocks as groundwater when it is stopped by an impermeable layer of rock.
The upper limit of this groundwater is known as the water table and the region of water-logged rock is known as an aquifer. The groundwater may slowly flow downhill through rock pores until it exits the surface as a spring or seeps into a stream or lake.