Water : Glossary

There are 59 documents in this section.

  • Endangered species

    16 March 2001

    Species of plants or animals threatened with extinction because their numbers have declined to a critical level as a result of overharvesting or because their habitat has drastically changed. That critical level is the minimum viable population (MVP), and represents the smallest number of breeding pairs required to maintain the viability of species.

  • Ecology

    16 March 2001

    Originally defined by Ernst Haeckel in 1866, ecology is the study of the relationships that develop among living organisms and between these organisms and the environment.

  • Conservation (nature)

    9 March 2001

    Protection against irreversible destruction and other undesirable changes, including the management of human use of organisms or ecosystems to ensure such use is sustainable.

  • Onchocerciasis

    29 January 2001

    Also known as river blindness; common in tropical regions of Africa and America; caused by infestation by a filarial worm (especially Onchocerca volvulus), transmitted by various species of blackfly, and characterised by subcutaneous nodules and very often blindness.

  • Distillation

    24 January 2001

    A process in which a liquid is vapourised and the vapour subsequently condensed to produce a purified form of the liquid or one of its constituents. Distillation is a natural part of the hydrological cycle. Energy supplied by the sun causes the water to evaporate. The vapour is carried up into the atmosphere until it is cool enough to condense as water droplets. These droplets are pure water, although the original source may have been salty or polluted. Distillation is the principal method of purifying liquids. It is the most common process used in desalination, and has been used increasingly by domestic consumers to provide fresh drinking-water.

  • Evapotranspiration

    24 January 2001

    The exchange of water between trees, soil and the atmosphere.

  • Flood

    24 January 2001

    The inundation of normally dry land by water. Flooding causes millions of dollars'-worth of property damage and takes hundreds of lives each year. It is most common in river valleys or along the coastal areas of lakes, seas and oceans. River floods are caused when a river channel is incapable of carrying the volume of water added to it, and the excess spills over on to the adjacent floodplain. Heavy and prolonged precipitation, snowmelt, channel constrictions, dam failures and alterations to drainage basins may produce or contribute to flooding. Global warming through the increased melting of glaciers and ice sheets, and the subsequent rise in sea level, has the potential to increase the frequency and extent of coastal flooding.

  • Grey water

    24 January 2001

    Waste water which does not contain the products of bodily functions, being mainly the product of bathing showering, dishwashing and similar activities. It is generally considered suitable for lawn and garden irrigation, and in areas such as the US south-west where water is scarce, it is seen as a simple way of increasing the efficiency of water use.

  • Hydrology

    24 January 2001

    The scientific study of water in the earth or atmosphere system. It includes not only surface water, but also water in the atmosphere and in the groundwater system. Physical hydrology focuses on the distribution and circulation of water, while applied hydrology is more concerned with water and human activities, and includes consideration of water quality, irrigation, drainage and erosion and flood control.

  • Floodplain

    24 January 2001

    An area of limited relief bordering a river inundated when the river overflows its bank during a flood. Floodplains are generally low and flat, but possess some relief in the form of the levées which border the main channel and the abandoned channels which indicate the former course of the river as it meandered across the floodplain.