Key terms - water cycle

• What is an anticyclone?


  A system of high pressure, causing high temperatures and unseasonably high evaporation rates.
• What is an aquifer?


  A permeable or porous rock which stores water.
• What is a channel flow?


  Water flowing in a rivulet, stream or river.
• What is convectional precipitation?


  Solar radiation heats the air above the ground, causing it to rise, cool and condense forming precipitation (often as thunderstorms).
• What is the cryosphere?


  The global water volume locked up within a frozen state (i.e. snow and ice).
• What is a depression?


  A system of low pressure, with fronts of precipitation where low and high pressure air masses meet.
• What is a desalination plant?


  The conversion of seawater to freshwater, suitable for human consumption.
• What is desublimation?


  The change of state of water from gas to solid, without being a liquid (the opposite process to sublimination).
• What is the drainage basin?


  The area of land drained by a river and its tributaries.
• What is the drainage density?


  The total length of all rivers and streams divided by the area of the drainage basin.
• What is a drought?


  An extended period of deficient rainfall relative to the statistical average for the region (UN).
• What is economic water scarcity?


  When water resources are available but insufficient economic wealth limits access to it.
• What is the ENSO cycles?


  El Nino Southern Oscillations - naturally occurring phenomena that involves the movement of warm water in the Equatorial Pacific.
• What is evapotranspiration?


  The combined total moisture transferred from the Earth to the atmosphere, through evaporation and transpiration.
• What is frontal precipitation?


  Where air masses of different temperatures meet at a front, one mass will be forced over another, causing precipitation beneath the front.
• What is the Global Hydrological Cycle?


  The continuous transfer of water between land, atmosphere and oceans. The Earth is a closed system.
• What is groundwater flow?


  Water moving horizontally through permeable or porous rock due to Gravity.
• What is a hydrological drought?


  Insufficient soil moisture to meet the needs of vegetation at a particular time.
• What is infiltration?


  The movement of water vertically through the pores in soil.
• What is Integrated drainage basin management?


  Establishing a frame of coordinated efforts between administrations (e.g. local government) and stakeholders (e.g. businesses) to achieve balanced management of a basin (World Bank).
• What is interception?


  Raindrops are prevented from falling directly onto the ground, instead hitting the leaves of a tree.
• What is a meteorological drought?


  When long-term precipitation trends are below average.
• What is a monsoon?


  The drastic variation between wet and dry seasons for sub-tropical areas, caused by a changed prevailing wind. Can lead to annual flooding.
• What is an open system?


  A system affected by external flows and inputs (such as a drainage basin, or a sediment cell).
• What is percolation?


  Water moving vertically from soil into permeable rock.
• What is physical water scarcity?


  A physical lack of available freshwater which cannot meet demand.
• What is relief precipitation?


  Precipitation caused when air masses are forced to rise over high land, determined by the relief/morphology of the land.
• What is a river regime?


  The pattern of river discharge over a year.
• What is runoff?


  Water flowing over the surface of the ground eg. after precipitation or snowmelt.
• What is salinisation?


  Where salt water contaminates freshwater stores or soils, creating saline conditions and reducing human use/consumption.
• What is saltwater encroachment?


  The movement of saltwater into freshwater aquifers or soils. This may be caused by sea level rise, storm surges or over-extraction.
• What is smart irrigation?


  Providing crops with a water supply less than optimal, to make crops resistant to water shortages
• What is a storm hydrograph?


  Variation of river discharge over a short period of time (days).
• What is sublimination?


  The change of state of water from solid to a gas, without being a liquid.
• What is a throughflow?


  Water moving horizontally through the soil, due to gravity.
• What is transpiration?


  The process through which water evaporates through the stomata in plants' leaves.
• What is water budget?


  The annual balance between inputs and outputs within a system.
• What is water conversation?


  Strategies to reduce water usage and demand.
• What is water recycling?


  The treatment and purification of waste water, to increase supply.
• What is water scarcity?


  There are limited renewable water sources (between 500 and 1000 cubic metres per capita per year).