Water Cycle

• How much water does the hydrosphere contain?

  1.4 sextillion litres of water
• Describe most of the water stored in the hydrosphere?

  Saline water in oceans

  Less than 3% is freshwater (which most of Earth's species need for survival)
• Of the Earth's fresh water, how much is FROZEN IN THE CRYOSPHERE?

  69% is frozen in the cryosphere
• Of the Earth's fresh water, how much is groundwater?

  30%
• what is groundwater?


  Water stored underground in the lithosphere
• Of the Earth's fresh water, how much is LIQUID FRESHWATER on the EARTH'S SURFACE?

  0.3% is liquid freshwater on the Earth's surface in lakes, rivers etc
• Of the Earth's fresh water, what % is stored as water vapour in the atmosphere??

  0.04%
• What must water be

  Physically and economically accessible for humans to use, and as a result, only a small amount of water on the planet can be used by humans
• Problem with groundwater


  Hard to access, so may not be cost effective to extract it
• What can water change between?

  Solid, liquid and gaseous forms
• What must water do for it to boil or melt?

  must gain energy (eg from the Sun)
• What must water do for it to condense or freeze

  lose energy
• What does water do continuously?

  water is continuously cycled between different stores. This is known as the GLOBAL HYDROLOGICAL CYCLE
• What type of system is the global hydrological system?

  closed systems- no inputs or outputs of water
• What does the amount of water present in each store vary over?

  A range of scales from LOCAL to GLOBAL
• What does the magnitude of each store depend on?

  the minimum amount of water flowing between them
• what can long-term changes in the climate affect?

  the magnitude of evaporation
• When does evaporation occur?

  When liquid water changes state into a gas, becoming water vapour.

  It GAINS energy (usually from solar radiation)
• What does evaporation cause an increase in?

  the amount of water stored in the atmosphere
• What does the magnitude of the evaporation flow vary by?

  Location & season. If there's lots of solar radiation, a large supply of water and warm, dry air, the amount of evaporation will be HIGH
• When will evaporation be LOW?

  If there's not much solar radiation, little available liquid water and COOL AIR that is already nearly saturated (unable to absorb any more water vapour)
• when does condensation occur?


  when water vapour changes state to become a liquid - it loses energy to the surroundings
• when does condensation happen?


  When air containing water vapour cools to to its dew point
• what is a dew point?


  the temperature at which water vapour will change from a gas to a liquis
• why do temps fall at night?


  due to heat being lost to space
• what can water droplets do?

  stay in the atmosphere or flow to other subsystem
• what does the magnitude of the condensation flow depend on?


  The amount of water vapour in the atmosphere and the temperature
• when is condensation high?


  • lots of water vapour in the air
  • if there is a large or rapid drop in temperature
• why is precipitation an essential part of the water cycle?


  Precipitation is the main flow of water from the atmosphere to the ground
• when do clouds form?

  When warm air cools down, causing the water vapour in it to condense into water droplets, which gather as clouds
• what happens when droplets get big enough?

  They fall as precipitation
• what THREE THINGS can cause warm air to cool, leading to precipitation?


  1. Other air masses
  2. Topography
  3. convection
• How do other air masses cause warm air to cool, leading to precipitation?

  Warm air less dense than cool air . as a result, when warm and cool air meet, the warm air - forced up above cool air

  it cools down as it rises

  results in FRONTAL PRECIPITATION
• How does TOPOGRAPHY cause warm air to cool, leading to precipitation?

  When warm air meets mountains, it is forced to rise, causing it to cool. = results in orographic precipitation
• How does CONVECTION cause warm air to cool, leading to precipitation?


  When sun heats up ground, moisture on ground evaporates and rises up in a column of warm air

  • As it gets higher, it cool
  • = results in convective precipitation
• Give details about water droplets caused by condensation?

  too small to form clouds on their own

  For clouds to form, must be tiny particles of other substances (eg dust, soot) to act as CLOUD CONDENSATION NUCLEI. They give water a surface to condense on . = ENCOURAGES clouds to form, rater than allowing the moist air to dispere
• What can vary SEASONALLY?

  Cloud formation and precipitation

  • can vary seasonally - more rain in winter
  • can vary by location - precipitation higher in tropics than poles
• give 2 examples of cryospheric processes?


  Accumulation

  Ablation
• what do cryospheric processes do?


  change the amount of water stored as ice in the cryosphere
• what varies with temp?


  the balance of accumulation and abblation