water cycle

• what is condensation?


  when water changes from a vapour into a liqhid as a result of a decrease in temperature
• what is evaporation?


  when water changes from a liquid to a vapour as a result of an increase in temp
• what is evapotranspiration?


  a combination of when water evaporates and/or is transpired by plants
• what is groundwater flow?

  the movement of water through porous rocks. water may stay here for thousands of years
• what is infiltration?


  when water enters the ground (due to gravity)
• what is a water table?

  the point in the soil or rock below which the ground is permanently saturated
• what is percolation?


  when water filters down through gaps in the soil and rocks (result of gravity)
• what is precipitation?


  water from the atmosphere (rain, snow, hail, sleet)
• what is transpiration?


  the transfer of water to the atmosphere through the leaves of a plant
• what is overland flow/surface runoff?

  water which does not infiltrate the ground but instead runs off along the surface
• what is stemflow?


  the movement of water along stems and tree trunks as it moves downwards due to gravity
• what is a drainage basin?


  an area of land that is drained by a river and its tributaries
• what is a source?


  where a river starts
• what is a tributary?

  a small branching stream that flows into a larger stream or river
• what is a distributary?

  a small branching stream that flows away from a main stream or river
• what is base flow?

  the water within a river which exists as a result of groundwater flow
• what is storm flow?

  the water within a river which exists as a result of a recent precipitation event
• what is lag time?


  the time between peak rainfall and peak discharge, when analyses on a storm hydrograph
• what is ablation?


  the loss of ice and snow through melting, evaporation and sublimation
• what is sublimation?


  the phase change of a substance from a solid to a vapour without passing through a liquid phase
• what is the water balance?

  the balance between inputs into a drainage basin and outputs
• what is the water balance equation?


  precipitation = evapotranspiration + streamflow +/- storage
• when does water surplus occur?

  when precipitation is greater than evapotranspiration and streamflow.
• when does water deficit occur?

  when precipitation is less than evapotranspiration and streamflow.
• water budget graph
• what is dynamic equilibrium?

  state of balance where a system is self-regulating
• why does it rain?

  when air rises, particles get cooler

  it gets cooler because particles spread out due to less pressure
• how does conventional rainfall occur?

  • sun heats ground

  • hot air rises

  • particles gain energy + expand

  • they rise

  • air cools and condenses forming clouds

  • rain can then occur
• how does relief rainfall occur?

  • topography or orographic uplift

  • topography of an area can cause clouds to form

  • when air is forced to rise over a barrier of mountains it cools & rises

  • layered clouds often form this way ie stratus
• how does convergence or frontal rainfall occur?

  • streams of air flowing from different directions are forced to rise where they flow together or converge

  • can cause cumulus clouds and showery conditions
• what are the 3 types of rainfall

  • conventional

  • relief

  • convergence/ frontal
• describe conventional rainfall 


  • sun heats ground

  • hot air rises

  • particles gain energy and expand

  • they rise

  • air cools and condenses forming clouds

  • rain then occurs
• describe relief rainfall

  • topography or orographic uplift
  • topography of an area can cause clouds to form
  • when air is forced to rise over a barrier of mountains it cools and rises
  • layered clouds often formed this way ie stratus
• describe convergence/ frontal rainfall

  • streams of air flowing from different directions are forces to rise where they flow together or converge
  • can cause cumulus cloud and showery conditions
• why does it rain

  • rains when air rises (evaporation)
  • particles get cooler at a rate of 6.5 degrees per kilometre
  • gets cooler because particles spread out due to less pressure
  • condensation forms clouds
• what is adiabatic expansion


  the expansion and subsequent cooling of air as it rises, causing an increase in volume and decrease in temperature
• what is lapse rate 


  the change of temperature of a parcel of air as it rises
• how does the lapse rate of air create clouds


  clouds form when rising air cools to its dew point, occurs when temp drops relative to the air around it
• what is dynamic equilibrium 


  state of balance where a system is self regulating
• processes within the WC

  • precipitation
  • interception
  • condensation
  • evapotranspiration
  • overland flow
  • evaporation
  • infiltration
  • throughflow
  • percolation
  • ground water flow