WATER CYCLE

• how is the drainage basin an example of the natural system?

  • In a drainage basin system its input is water entering the system through rain. The systems boundary is the watershed. Water travels from the drainage basin to the river and then the river flows. Its output is where the river meets the sea.
• subsystems in the Earth

  • cryosphere
  • lithosphere
  • biosphere
  • hydrosphere
  • atmosphere
• The Earth is a cascading system - matter and energy move from one subsystem to the next
• water cycle on a local scale - inputs

  precipitation

  • convectional
  • relief
  • frontal
• what is convectional rainfall?

  due to the heating of the sun , warm air rises , condenses and falls as rain
• what is relief rainfall?

  warm air is forced upwards by a barrier such as mountains where it condenses at higher altitudes - falls as rain
• what is frontal rainfall?

  Frontal rainfall is precipitation that occurs when warm and cold air masses meet, causing the warm air to rise and cool, leading to condensation and rainfall.
• flows in a local water scale

  • surface runoff
  • infilitration
  • percolation
  • throughflow
  • groundwater flow
  • stemflow
• stores in a local water scale

  • freshwater stores
  • ground water stores
  • ice sheets - Greenland
• outputs in a local water scale

  • evapotranspiration
• size of hydrosphere

  97%
• size of cyrosphere

  69%
• size of lithosphere

  30% groundwater
• size of freshwater stores

  0.3%
• size of atmosphere size

  0.04% in water vapour
• exampls of stores in the hydrological cycle

  • lakes
  • oceans
  • aquifers
  • ice sheets
• examples of transfers in the hydrological cycle

  • evapotranspiration
  • runoff
  • groundwater flow
  • percolation
• dew point


  temperature when air is saturated
• flows of water within the water cycle

  • evaporation
  • condensation
  • cloud formation and precipitation
  • cryospheric processes
• flow of evaporation

  • increases amount of water stored in the atmosphere
  • magnitude of evaporation varies by location and season
  • higher rates of evaporation - lots of solar radiation , large supply of water and warm air
  • lower rates of evaporation - lack of solar radiation , small supply of water and cool air
• evaporation - liquid to gas
• condensation - vapour to liquid
• flow of condensation

  • happens when air containing water vapour cools to dew point
  • decreases water stored in atmosphere - water vapour stays in atmosphere or flows to other subsystems such as water vapour condensing and forming dew on leaves
  • high amounts of condensation - lots of water vapour in air or large or rapid drop in temperature
• flow of cloud formation and precipitation

  • clouds form when warm cools down , causing water vapour in it to condense into water droplets = gather as clouds. Droplets become big enough to fall as rain
  • cloud formation and precipitation depends on seasons (UK =more rainfall in winter) and location (rainfall higher in tropics)
• what do clouds need to form?

  tiny particles of substance e.g dust or soot to as act as cloud condensation nuclei. Gives the water surface to condense on
• flows of cryospheric processes

  • processes such as accumulation + ablation change amount of water stored in cyrosphere - balance of these processes change with temperature
• how does temperatures affect the cryosphere?

  • periods of global cold - inputs outweigh outputs
  • warmer global temperatures - magnitude of stores decrease as losses (due to melting of ice) are larger than inputs of snow
• boundary of a drainage basin

  watershed - any rain that falls beyond watershed enters different drainage basins
• inputs to drainage basin

  precipitation
• outputs to drainage basin

  • runoff
  • evaporation
  • transpiration
• stores in a drainage basin

  • lake storage
  • groundwater
  • absorption by vegetation
  • channel storage
  • soil storage
  • interception by vegetation
• drainage basin store - lake storage

  water = travels overland or via river channel or precipitation can fall directly into lake
• drainage basin store - groundwater

  water stored within permable rock underground , enters through gaps between grains in sandstone or down joints and cracks in limestone
• drainage basin store - absorption by lakewater

  vegetation can absorb water from the soil , river channels or overland flows via root systems
• drainage basin stores - channel storage

  volume of water contained within banks of rivers will operate as a water store between its initial input and ultimate output
• drainage basin stores - soil storage

  water can be stored in or around soil particles in the pedosphere
• drainage basin stores - interception by vegetation

  leaves , stems or trunks of vegetation = act as barrier of precipitation reaching land's surface. It temp stores water.

  • more dense vegetation = more likely water will NOT reach the surface
• transfers in a drainage basin system

  • surface runoff
  • infilitration
  • percolation
  • through flow
  • groundwater flow
  • transpiration
• what is the water balance?

  difference in inputs (precipitation) and outputs (channel discharge and evapotranspiration)
• how is the water balance affected in wet seasons?

  • precipitation exceeds evaporation = water surplus
  • ground stores fill with water = more surface runoff , higher discharge and river levels rise