Water : Glossary

There are 59 documents in this section.

  • Condensation

    23 January 2001

    Condensation in the environment is most frequently associated with the change of water vapour into liquid water in the atmospheric environment. It is generally brought about by cooling, which reduces the ability of the atmosphere to absorb and retain water vapour. If a parcel of air containing a specific volume of water vapour is progressively cooled, it will reach a temperature at which it is completely saturated - the dewpoint temperature of that parcel of air. Any additional cooling beyond the dewpoint will cause the condensation of some of the vapour.

  • Dams

    23 January 2001

    Structures designed to restrict the flow of surface runoff, usually to control flooding or to provide water for irrigation or the production of hydroelectricity. They range from relatively small earth-fill features, pounding back thousands of cubic metres of water, to massive reinforced concrete structures which create reservoirs containing several billion cubic metres of water. All dams, large or small, have an environmental impact on the area in which they are built. The obvious change is in the hydrological cycle, but environmental interrelationships ensure that the effects are felt in the local climatology and in the flora and fauna of the region.

  • Delta

    23 January 2001

    A depositional landform created when a river or stream flows into a body of standing water, such as a lake or sea. The sudden reduction in the velocity of the stream which results causes it to deposit the sediment it is carrying.

  • Desalination

    23 January 2001

    The removal of dissolved salts from sea water or saline groundwater to provide fresh water for domestic, industrial or agricultural use.

  • Aquifer

    8 December 2000

    A layer or section of earth or rock that contains freshwater, known as groundwater - any water that is stored naturally underground or that flows through rock or soil, supplying springs and wells.

  • Hydrological cycle

    8 December 2000

    The natural cycle by which water evaporates from the oceans and other water bodies, accumulates as water vapour in clouds, and returns to oceans and other water bodies as precipitation. Precipitation over land has two components: runoff and moisture from evapotranspiration.

  • Non-renewable water

    8 December 2000

    Water in aquifers and other natural reservoirs that are not recharged by the hydrological cycle or are recharged so slowly that significant withdrawal for human use causes depletion. Fossil aquifers are in this category: They recharge so slowly over centuries that they are, in effect, a non renewable resource.

  • Renewable water

    8 December 2000

    Freshwater that is continuously replenished by the hydrological cycle for withdrawal within reasonable time limits, such as water in rivers, lakes or reservoirs that fill from precipitation or from runoff. The renewability of a water source depends both on its natural rate of replenishment and the rate at which the water is withdrawn for human use.

  • Runoff

    8 December 2000

    Water originating as precipitation on land that then runs off the land into rivers, streams, and lakes, eventually reaching the oceans, inland seas, or aquifers, unless it evaporates first. That portion of runoff that can be relied on year after year and easily used by human beings is known as stable runoff.

  • Water consumption

    8 December 2000

    Use of water that results in its evaporation or transpiration (through plants) or that otherwise makes it unavailable for subsequent human use.