Freshwater
The drainage basin as an open system with inputs (precipitation of varying type and
intensity), outputs (evaporation and transpiration), flows (infiltration, throughflow,
overland flow and base flow) and stores (including vegetation, soil, aquifers and the
cryosphere)
Drainage basin:
An area within which water supplied by precipitation is transferred to the ocean,
lake or larger stream
Includes all of the area that is drained by a river and its tributaries
Divided by watersheds, imaginary lines separating adjacent basins
Some rivers drain into the sea but others drain into an inland depression - these
drainage basins are endorheic or closed (e.g. Okovango)
Open system as it allows movement of energy and matter across its boundaries
Hydrological cycle: cycle of water between the biosphere, atmosphere, lithosphere
and hydrosphere
Inputs:
Precipitation: includes all forms of rainfall, snow, frost, hail and dew
Conversion and transfer of moisture in the atmosphere to the land
Main characteristics of precipitation affecting hydrology:
o Total amount of precipitation
o Intensity
o Type (snow, rain etc.)
o Geographic distribution
o Variability
Other inputs: irrigation water, water transfer schemes, desalinated water
Outputs:
Evaporation:
Process by which a liquid or solid is changed into a gas
Most important from oceans and seas
Increases under warm, dry conditions and decreases under cold, calm conditions
Factors affecting evaporation:
o Temperature
o Humidity
o Wind speed
o Amount of water available
o Vegetation cover
o Colour of the surface/albedo
Evapotranspiration (EVT):
Combined effect of evaporation and transpiration (water vapour escaping from living
plants)
Most important aspect of water loss, nearly 100% of annual precipitation in arid
areas and 75% in humid areas
The drainage basin as an open system with inputs (precipitation of varying type and
intensity), outputs (evaporation and transpiration), flows (infiltration, throughflow,
overland flow and base flow) and stores (including vegetation, soil, aquifers and the
cryosphere)
Drainage basin:
An area within which water supplied by precipitation is transferred to the ocean,
lake or larger stream
Includes all of the area that is drained by a river and its tributaries
Divided by watersheds, imaginary lines separating adjacent basins
Some rivers drain into the sea but others drain into an inland depression - these
drainage basins are endorheic or closed (e.g. Okovango)
Open system as it allows movement of energy and matter across its boundaries
Hydrological cycle: cycle of water between the biosphere, atmosphere, lithosphere
and hydrosphere
Inputs:
Precipitation: includes all forms of rainfall, snow, frost, hail and dew
Conversion and transfer of moisture in the atmosphere to the land
Main characteristics of precipitation affecting hydrology:
o Total amount of precipitation
o Intensity
o Type (snow, rain etc.)
o Geographic distribution
o Variability
Other inputs: irrigation water, water transfer schemes, desalinated water
Outputs:
Evaporation:
Process by which a liquid or solid is changed into a gas
Most important from oceans and seas
Increases under warm, dry conditions and decreases under cold, calm conditions
Factors affecting evaporation:
o Temperature
o Humidity
o Wind speed
o Amount of water available
o Vegetation cover
o Colour of the surface/albedo
Evapotranspiration (EVT):
Combined effect of evaporation and transpiration (water vapour escaping from living
plants)
Most important aspect of water loss, nearly 100% of annual precipitation in arid
areas and 75% in humid areas
