Water on Earth

what percent of earth's surface is covered with water?

out of this, what is the persent of potable water?

out of this, what is the rate of water re-use?

One thought on “Water on Earth

  1. First, according to WorldAtlas.com


    the basic measurements of the Earth's surface are as follows:

    "Surface Area of the Planet (510,066,000 sq km)

    Land Area on the Planet (148,647,000 sq km) 29.1%

    Ocean Area (335,258,000 sq km)

    Total Water Area (361,419,000 sq km) 70.9%

    Type of Water (97% salt), (3% fresh)"

    So the answer to your first question is that 71% of the Earth's

    surface is covered with water. Taking "potable" water to be fresh

    water as opposed to salt water, 3% of that total is potable.

    Obviously, much of that water is not, in fact, immediately potable,

    but relatively inexpensive filtering and purification systems are

    sufficient to treat most of it. Making salt water potable is still a

    much more expensive undertaking.

    I'm not sure exactly what you mean by the rate of water re-use. In

    general, water naturally cycles through the environment with a lot of

    different time-scale. Some can be trapped for thousands or even

    millions of years in glaciers, ice-caps, underground reservoirs and

    aquifers (if you're interested, you can read about so-called "fossil

    water" at a number of sites; just do the Google search:

    http://www.google.com/search?q="fossil water" ).

    Most surface water is recycled on a much shorter time scale by

    weather, river flow, ocean currents and biological processes. See, for

    example, "Water Science for Schools" at the USGS website:


    There are still a lot of different time scales at work. For example,

    there are daily cycles as water condenses and falls as rain or dew and

    re-evaporates, and there are yearly cycles as water accumulates in

    mountain snow pack, then melts and flows back to the sea. Water is

    also important to a great many chemical reactions, so some water is

    converted to other molecules and other molecules are converted to

    water. Given the huge volume of water that exists on the planet, even

    though a lot of water may participate in such reactions, it probably

    has only a minor influence on the global water cycles.

    Then, of course, you could talk about human use, contamination and

    recovery via wastewater treatment facilities. You might also want to

    know something about the availability of potable drinking water around

    the world and the problems of water availability relative to

    population density. Natural processes don't always concentrate water

    in excess quantities everywhere where people choose to live. This can

    generate a lot of conflict and even war. See, for example the

    chronology of water-related conflicts at WorldWater.org:


    Other searches which will generate further information:




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