Answer:
The Earth has a finite amount of water. The water that is here today is the same water that will be here in 20 or even 20 million years’ time. So, if all living things use water, how is it that we don’t use up all our water? The answer is that water is constantly recycled through the Earth’s system through a process called the water cycle.
Dynamic and complex: the global water cycle
Water in the Earth system is influencing all aspects of life on Earth. Pathways, storage, transfers and transformations have an effect on the global climate and human welfare. Within this interactive 4 scientists talk about some of the complex aspects of the water cycle.
To use this interactive, move your mouse or finger over any of the labelled boxes and click to obtain more information.
The water cycle encompasses a number of processes that circulate water through the Earth’s subsystems. Water evaporates from within soils and through vegetation and from bodies of water (such as rivers, lakes and oceans). This evaporated water accumulates as water vapour in clouds and returns to the Earth as rain or snow. The returning water falls directly back into the oceans, or onto land as snow or rain. It soaks into the soil to move into the groundwater or runs off the Earth’s surface in streams, rivers and lakes, which drain back into the oceans. The water may be taken up by plants and returned to the atmosphere through processes like transpiration and photosynthesis. Water may also be returned to the atmosphere through the combustion of plants in fossil fuel.
Explanation:
ARTICLE The water cycle EXPLORE
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The Earth has a finite amount of water. The water that is here today is the same water that will be here in 20 or even 20 million years’ time. So, if all living things use water, how is it that we don’t use up all our water? The answer is that water is constantly recycled through the Earth’s system through a process called the water cycle.
Dynamic and complex: the global water cycle
Water in the Earth system is influencing all aspects of life on Earth. Pathways, storage, transfers and transformations have an effect on the global climate and human welfare. Within this interactive 4 scientists talk about some of the complex aspects of the water cycle.
To use this interactive, move your mouse or finger over any of the labelled boxes and click to obtain more information.
The water cycle encompasses a number of processes that circulate water through the Earth’s subsystems. Water evaporates from within soils and through vegetation and from bodies of water (such as rivers, lakes and oceans). This evaporated water accumulates as water vapour in clouds and returns to the Earth as rain or snow. The returning water falls directly back into the oceans, or onto land as snow or rain. It soaks into the soil to move into the groundwater or runs off the Earth’s surface in streams, rivers and lakes, which drain back into the oceans. The water may be taken up by plants and returned to the atmosphere through processes like transpiration and photosynthesis. Water may also be returned to the atmosphere through the combustion of plants in fossil fuel.
The dynamic water cycle
In this video, four New Zealand scientists – Dave Campbell, Louis Schipper, David Hamilton and Keith Hunter – talk about how only a small percentage of the Earth’s water is freshwater, and of that small percentage, only a fraction is available for human use.
Water and the atmosphere
Water enters the atmosphere through evaporation, transpiration, excretion and sublimation:
Transpiration is the loss of water from plants (via their leaves).
Animals excrete water by respiration and by passing urine.
Sublimation is when ice or snow transforms directly into water vapour without going through a liquid phase (i.e. they do not melt).
Water commonly occurs in the atmosphere in the form of water vapour. If it cools down, it can condense, accumulating in clouds. As the clouds grow, they become heavier and can fall back to the Earth as precipitation (rain, snow, hail or sleet) or re-evaporate back into vapour.
Water and the biosphere, hydrosphere and geosphere
When water returns to Earth, it can either enter the hydrosphere or the geosphere.