Hydrological Cycle - The Global Hydrological Cycle

The Cycle:
  1. Inputs: Precipitation – rain and snow
  2. Flows: Movement of water in contract with the land on the ground
  3. Stores: Lakes, reservoirs, aquifers, seas and oceans
  4. Outputs: Evaporation, transpiration and river outflows.
  • Can be challenged at a local, regional and global scale. It can change depending on the size of the location.
Hydrological Cycle And Energy:
  • Sunlight is the main energy source. Sunlight provides heat energy for evaporation from oceans. It also causes transpiration which is important for rainforests.
  • This drives the system and provides clouds
  • Gravitation Potential Energy is the next form of energy. This is all the water at the height that is released as it falls to the earth. Therefore rain falls and rivers flow to the sea.
Importance Of Size Of Shores:
  • Oceans have 95% water but it cannot be used fully e.g saltwater cannot be drunk.
  • The atmosphere has a small store which is important for transporting water
  • Surface freshwater flows are important to spread water to areas without precipitation and for those areas without human uses for water.
  • Groundwater is a large store and it can be very useful for humans
  • The cryosphere is the second largest store but it is less dynamic than the oceans as water can be frozen. This is now becoming more important due to climate change and ice melt increasing.
Fluxes:
  • The speed of change or movement of water between stores. Measured in gigatons
  • Biggest fluxes = evaporation over the oceans. Second biggest fluxes = precipitation over the ocean
  • The ones over the land are important as they bring rain to the land areas and balance the system
Global Water Budget:
  • Different places have different amounts of water available at different times of the year
  • Amount of water available = water budget. There can be a surplus or a deficit.
  • Lots of stores = no deficit. Big deficits can be in countries where there are hot deserts where precipitation is low but evaporation is high. Humans can’t access water all the time
  • The more developed a society is the more consumption of water they have.
Residence Times:
  • Different stores have different residence lines. How long on average can water molecules stay in the reservoir. Cryosphere has long shores
  • Short residence time is for atmospheric stores e.g water that evaporates quickly
  • Can determine how accessible water is for humans. Shorter residence = faster flux to access the water e.g farmers using river waters.
  • Some stores are not replenished on a human scale and are considered non-renewable as if they are exploited than it will run out. 

     


at