Hydrologyand

FluvialGeomorphology

HYDROLOGICAL CYCLE

Condensation

What is hydrological cycle?

• The movement of moisture and energy BETWEENair, 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

Transpiration

A process by which plants lose water vapour into the air through their leaves or stems

Evapotranspiration

The total loss of moisture from an area

by direct evaporation

and transpiration

Evapotranspiration (EVT)

Potential EVT

• The amount of water that could be lost by evapotranspiration.

• For example, it is potentially high EVT in deserts, but the amount that can take place is limited due to the minimal moisture available.

Actual EVT

• Is what actually occurs.

• In the UK there is more water available for evapo-transpiration than takes place

CONDENSATION

A process of the change of water vapour into water

–Transported water vapourand 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. Evaporationb. Transpirationc. Condensationd. Precipitatione. Percolationf. Groundwaterg. Run-off (18)

3. Explain why hydrological cycle is a closed system. (5)