5.1C Global water budget

• global water budget is the difference between the inputs and outputs from the different stores
• Residence times

  • The time water is held in a store is called the residence time
  • The size of the stores of water along with water residence time is dictated by:
  • Flows/transfers such as evaporation
  • Global factors such as climate change
  • Local factors such as human activity on a hillslope
• Flows/transfers

  • Any change in the flow/transfer of water impacts the size of the water store and residence time of water
  • More precipitation generally increases the availability of water for storage
  • If the rainfall is too intense and surface flow increases, the opportunity for infiltration and water storage less 
• Inter-tropical convergence zone:

  • a low air pressure zone
  • tracks with the seasonal movement of the Sun, north and south of the equator bringing intense low-pressure rain/monsoon conditions with the movement

  
• Cryospheric processes

  • The second largest store of water is ice and 95% is locked as the ice sheets of Antarctica and Greenland
  • The total melting of the ice sheets could result in a 60 m sea level rise
  • Melting of the ice sheets adds water to the hydrosphere store of the oceans
  • Ice shelves are further destabilised, which triggers ice calving, these icebergs subsequently melt; adding to the hydrosphere store and rising sea levels
  • This is a positive feedback loop