What is hydrological cycle?• The movement of moisture and energy BETWEEN air, land and sea.• Oceans, rivers, clouds and rain – all contain water in a frequent state of change.• The circulation and conservation of water from the land to the sky and back again• An example of a system which a set of components is linked
How does the hydrological cycle work?• The components of the cycle are: – Evaporation – Transpiration – Evapotranspiration – Potential EVT – Actual EVT – Condensation – Precipitation – Percolation – Groundwater – Run-off
Evaporation• A process by which water is converted from its liquid form to gaseous form• transferred from land and water masses to the atmosphere.• Evaporation from the oceans accounts for 80%• 20% coming from inland water and plant surfaces.
Evaporation• Wind speed: the higher the wind speed, the more evaporation• Temperature: the higher the temperature, the more evaporation• Humidity: the lower the humidity, the more evaporation
TranspirationA process bywhich plantslose watervapour into theair throughtheir leaves orstems
Evapotranspiration The total loss of moisture from an area by direct evaporation and transpiration
Evapotranspiration (EVT) Potential EVT Actual EVT• The amount of water • Is what that could be lost by actually evapotranspiration. occurs.• For example, it is • In the UK there is more potentially high EVT water in deserts, but the available for amount that can take evapo- place is limited due transpiration to the minimal than takes moisture available. place
CONDENSATIONA process of the change ofwater vapour into water–Transported water vapour and forms tiny droplets in clouds
Precipitation• The deposition of moisture from the atmosphere on the earth’s surface• The most important input into the system forms includes snow, hail, rain, and fog.
Percolation• The process by which the rain water soaks through the soil into the rocks• Water moves downward• Infiltrates through soil until reaches water table• Water in the soil does not remain there but moves down slowly into the lower layers of soil and rock.• It creates groundwater storage found in rocks and this may later be moved sideways through the rock via groundwater flow.
Groundwater• The place where water is stored underground in the rock• Some of the groundwater is trapped between rock or clay layers• Water that infiltrates the soil flow downward until it encounters impermeable rock then travels laterally• The location where water moves laterally is known as ‘aquifers’
Run-off•the water that returns to the land which flows downhill or on the surface of earth
At a global scale, the hydrological cycle is a closed system• Water is circulated continuously fuelled by energy from the sun• No effective gains or loses• Fixed amount of water
Exercise1. Define hydrological cycle. (2)2. Draw a well-labelled with brief explanation of the following on the diagram: a. Evaporation b. Transpiration c. Condensation d. Precipitation e. Percolation f. Groundwater g. Run-off (18)3. Explain why hydrological cycle is a closed system. (5)