Key Definition

• Anticyclone


  A system of high pressure, causing high temperatures and unseasonably high evaporation rates
• Aquifer


  A permeable or porous rock which stores water
• Channel Flow


  Water flowing in a rivulet, stream or river
• Convectional Precipitation


  Solar radiation heats the air above the ground, causing it to rise, cool & condense forming precipitation (often as thunderstorms)
• Cryosphere


  The global water volume locked up within a frozen state (i.e. snow and ice)
• Depression


  A system of low pressure, with fronts of precipitation where low and high pressure air masses meet
• Desalination Plant


  The conversion of seawater to freshwater, suitable for human consumption
• Desublimation


  The change of state of water from gas to solid, without being a liquid (the opposite process to sublimation)
• Drainage Basin


  The area of land drained by a river and its tributaries
• Drainage Density


  The total length of all rivers & streams divided by the area of the drainage basin
• Drought


  An extended period of deficient rainfall relative to the statistical average for the region (UN)
• Economic Water Scarcity


  When water resources are available but insufficient economic wealth limits access to it
• ENSO Cycles


  El Nino Southern Oscillations - naturally occurring phenomena that involves the movement of warm water in the Equatorial Pacific
• Evapotranspiration


  The combined total moisture transferred from the Earth to the atmosphere, through evaporation and transpiration
• Frontal Precipitation


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


  The continuous transfer of water between land, atmosphere and oceans. The Earth is a closed system
• Groundwater Flow


  Water moving horizontally through permeable or porous rock due to Gravity
• Hydrological Drought


  Insufficient soil moisture to meet the needs of vegetation at a particular time
• Infiltration


  The movement of water vertically through the pores in soil
• 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)
• Interception


  Raindrops are prevented from falling directly onto the ground, instead hitting the leaves of a tree
• Meteorological Drought


  When long-term precipitation trends are below average
• Monsoon


  The drastic variation between wet and dry seasons for sub-tropical areas, caused by a changed prevailing wind. Can lead to annual flooding
• Open System


  A system affected by external flows and inputs (such as a drainage basin, or a sediment cell)
• Percolation


  Water moving vertically from soil into permeable rock
• Physical Water Scarcity


  A physical lack of available freshwater which cannot meet demand
• Relief Precipitation


  Precipitation caused when air masses are forced to rise over high land, determined by the relief/ morphology of the land
• River Regime


  The pattern of river discharge over a year
• Runoff


  Water flowing over the surface of the ground eg. after precipitation or snowmelt
• Salinisation


  Where salt water contaminates freshwater stores or soils, creating saline conditions and reducing human use/ consumption
• Saltwater Encroachment


  The movement of saltwater into freshwater aquifers or soils. This may be caused by sea level rise, storm surges or over-extraction
• Smart Irrigation


  Providing crops with a water supply less than optimal, to make crops resistant to water shortages
• Storm Hydrograph


  Variation of river discharge over a short period of time (days)
• Sublimation


  The change of state of water from solid to a gas, without being a liquid
• Throughflow


  Water moving horizontally through the soil, due to gravity
• Transpiration


  The process through which water evaporates through the stomata in plants' leaves
• Water Budget


  The annual balance between inputs and outputs within a system
• Water Conservation


  Strategies to reduce water usage and demand
• Water Recycling


  The treatment and purification of waste water, to increase supply
• Water Scarcity


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