The Global Hydrological Cycle

The Global Hydrological Cycle
Draw and describe the Global
Hydrological Cycle.
Explain how a balance is maintained
within the Global Hydrological Cycle.
Water as a finite resources
• 1.4 billion cubic kilometres of water within
the planets hydrosphere.
• 3% is freshwater.
• 77.2% of this is in cold storage.
• 22.4% is in groundwater storage.
• 0.35% in lakes and swamps.
• 0.01% in rivers and streams.
Uneven distribution of water
• A small amount available for human use
and consumption.
• Usually in the wrong place and the wrong
• From earliest times people have sought to
harness and control the rivers.
Hydrological Cycle
Evaporation: The transfer of water from the sea to the air as water vapour.
•Condensation: Water vapour (gas) changes back into water (liquid). It forms
small droplets which are visible as clouds.
•Precipitation: Water falls to earth as either liquid (rain) or in a frozen state
(snow, hail).
•Stream / Surface Run Off: Most water returns to the sea in the form of
•Evapotranspiration: evaporation of moisture from vegetation
•Ground water Flow: Some water returns to the sea as groundwater through soil
and rocks.
•Infiltration: The point at which rainfall seeps into soil.
•Percolation: The seepage of water downwards through rocks.
•Throughflow: The movement of water downwards through soil back to the sea.
•Groundwater Zone: Storage area for water which is slowly released back to
the sea via springs and rivers.
•Interception – When precipitation is prevented from falling to the surface by
leaves/dense forests.