Posts Tagged 'Water Facts and Figures'

Water – Nature’s Abundant Gift?

Water is a mysterious but crucial substance.  Its origins and properties still evoke debate, despite its existence by some accounts dating back 3.8 Billion years.  Its forms alone are worthy of investigation. Water is the only substance whose solid form is less dense than its liquid, carrying tremendous implications for aquatic life.  In any of its forms, it can not be created, destroyed, nor leave the earth.  As such, it exists in a closed cycle known as the hydrosphere.  In the hydrological cycle, water circles through the earths system of reservoirs.  These reservoirs are numerous and well known, including: atmosphere (clouds and rain), oceans, lakes, rivers, ground water, icecaps, saturated soil and subterranean aquifers.  The water moves between these various reservoirs through the process of evapotranspiration, a name used to encompass the processes of evaporation (from oceans), sublimation (from lakes/rivers) and transpiration (from vegetation).

Figure 1. The hydrological cycle. (Trenberth et al. 2006a).

Between the numerous reservoirs, just how much water exists on the earth is a difficult number to determine.  It is impossible to know exactly.  Water trapped below the surface and that locked in ice caps and perma frost can never be measured exactly.  One of the best known estimates comes from Igor Shikloanov from the State Hydrological Institute in St. Petersburg.  His self admittedly crude estimate hits the 1.4 billion cubic km mark.  However, this huge number is misleading if not understood.  To represent that amount that is available for human consumption, more than 97% must be removed because ocean water is too salty to drink or use for irrigation.  A remaining 2.5% , or about 35 million cubic km is found in a freshwater state.  Unfortunately, this figure too requires further reduction.  At any one time, a small percent of the total is in the form of rain, clouds, fog or tied up in the biosphere.  An even more noteworthy chunk occupies 75% of the small freshwater total, locked and unusable in polar ice caps and tundra snow cover. Freshwater lakes and rivers, the renewable source we are concerned about preserving is a mere 90 000 cubic kilometers (a mere .26% of an already small 2.5% source).

A mere 0.26 percent of the water on Earth is drinkable.

Marg De Villers, author of award winning Water, creates a vivid image to make the numbers more manageable.  If all the worlds water was to be held in a 5L container, the usable freshwater source would occupy only a teaspoon.

When we know what we are working with, the need for conservation and proper management becomes overwhelmingly apparent.


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