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The Drainage Basin: localised cycle and an open system - Coggle Diagram
The Drainage Basin:
localised cycle and an open system
Inputs: Precipitation
Orographic rainfall
High relief areas for warm air to rise. It cools and condenses so falls as rain before getting over the peak. Afterwards air falls again and becomes warmer causing drier conditions (rain shadow) eg. California
Convectional rainfall
Intense sunlight heats the ground which heats the surrounding air. Air rises due to convection and cools. As water condenses huge dense clouds form and heavy rain falls eg. Tropics
Frontal rainfall
A warm front meets a cold front which forces warm air to rise. It cools, condenses and falls as rain eg. UK
Physical factors affecting inputs:
Type/intensity/amount/distribution of precipitation
Seasonality ie, monsoon season, drought season
Variability: Secular (long-term), Periodic (seasonally, annually) Stochastic (random)
Flows
Interception
process by which water is stored in vegetation
Affected by:
Rate of precipitation-
short/light rainfall= most interception
Vegetation cover and type-
greater amount= more interception. Denser types= more interception
Seasons-
summer= more due to vegetation cover
Throughflow
the lateral transfer of water down slope through the soil.
(percolines= lines of conc. water flow)
Affected by:
Number of percolines
Soil structure
Percolation
deep transfer of water into rock
Affected by:
Geology-
more permeable rock= more percolation
Infiltration
process by which water soaks into the soil.
Infiltration capacity
max rate at which soil can absorb precipitation
Affected by:
Duration of rainfall-
light rain= more infiltration
Antecedent soil moisture-
previously saturated soil= less infiltration
Soil structure-
sandy = more, clay=less
Relief-
flatter surface= more
Direct runoff
rapid flow of water over the land. Occurs when amount of precipitation exceeds the infiltration rate capacity of the soil
Affected by:
Relief
Antecedent soil moisture
Amount of precipitation
Saturated overland flow
slower transfer process than direct runoff. Result of the upward movement of the water table into the evaporation zone
Groundwater flow
very slow transfer of percolated water through porous rock.
Affected by:
Geology-
more porous rock= more ground flow
Relief-
flatter surfaces influence infiltration which influences groundwater flow
Soil structure-
looser soil= more ground flow
Outputs
Evaporation
process by which moisture is lost directly into the atmosphere
Transpiration
biological process by which water is lost from plants
Channel flow
the flow of water in streams or rivers
Physical factors affecting outputs:
Climate- hotter= more evaporation/transpiration
Type of vegetation/ amount of vegetation cover
Size of body of water
Human impact
Urbanisation
Concrete/tarmac = less infiltration/percolation and more direct runoff. Affects flows and stores
Less vegetation= less interception/transpiration
More direct runoff= increased flood risk
Due to lack of infiltration more evaporation. Cities are also usually warmer.
Deforestation
Removal of vegetation= less transpiration/interception
Exposed land= more infiltration, percolation and throughflow
Less evaporation as water does not collect on the surface
Varying rates of direct runoff depending on infiltration rate
Reservoir creation/channel management
Increases rate of evaporation
Reduces river flow
Over-abstraction of water also reduces river flow, more evaporation