Drainage Basin: Elements

 Inputs, Outputs, Transfers, Storage...Woahhh

Characteristics of the Drainage Basin

• Inputs: in the form of precipitation and snow
• Outputs: this is where water is lost from the system, either through being carried to sea (by rivers) or through evapotranspiration. 

Within the system some water is:

• Stored: In rivers, soil, vegetation.
• Transferred: Infiltration, through-flow etc. 

Key:    INPUT

            STORAGE

            TRANSFERS

            OUTPUTS

Precipitation

This term refers to the act of water/moisture (in its solid or liquid form) falling from clouds in the sky. 

Examples include: Rain, hail and snow. 

Influencing Factors:

• Presence of Vegetation 
• Time of Year
• Altitude 
• Latitudinal Location

Evaporation

This is the process by which the suns energy converts water into water vapour.

Influencing Factors:

• Atmospheric Conditions (temperature, humidity, hours of sunshine, wind speed)
• Time of Year

Transpiration

This a biological process by which water is lost from a plant through the stomatas on the leaves. 

Influencing Factors: 

• Type of vegetation
• Vegetation density/coverage 
• Availability of moisture 

Evapotranspiration (EVT)

This is the process by which water is loss from both water bodies and vegetation. 

• Actual EVT: The exact amount of water being converted to water vapour
• Potential EVT: The amount of water than can be (potentially) converted into water vapour

Interception

Refers to water that caught and stored by vegetation. Interception loss is the water that is retained on plant surfaces and never enters the system. 

Other terms to note:

• Through-fall: Water falling between the gaps of leaves
• Stem-flow: Water flowing along the stems of plants and trunks of trees

Influencing Factors:

• Presence of Vegetation
• Type of Vegetation
• Volume of precipitation 

Infiltration

This is the downward movement of water from the surface, into the soil (subsurface). The maximum rate at which rain can be absorbed via the soil mm/hr is known as its infiltration capacity. 

Influencing Factors: 

• Permeability 
• Duration of precipitation 
• Intensity of precipitation
• Raindrop size
• Angle of slope 
• Vegetation Cover

Other terms to note:

Through flow: The lateral movement of water through the soil layer. 

Antecedent Precipitation: Water already present in the soil