Lesson 2 - Factors Affecting Drainage Basin Flashcards
What are the 3 types of rainfall?
Convectional
Cyclonic
Orographic
What is convectional rainfall?
Land gets warmer, air expands + rises
Air cools loses ability to hold water vapour
Condensation occurs, clouds develop
Rain as a result
What is cyclonic rainfall?
Warm air forced to rise over cold air
Warm air is lighter, less dense
Air cools, condenses + forms clouds as it rises
What is orographic rainfall?
Air forced to rise over a natural barrier
Cools, condenses + forms clouds
Heavy rain on higher lands
Leeward slope receives relatively little rainfall
What is the Rain Shadow Effect?
Orographic rainfall
Downwind/leeward slope receives little rainfall
Which human practices have the largest impact within the drainage basin?
Cloud Seeding
Urbanisation
Dam Construction
Deforestation + Afforestation
Groundwater Abstraction
How does cloud seeding affect the drainage basin?
Influences amount + intensity of precipitation
What is cloud seeding?
Atmospheric dispersal of substances that serve as ‘Cloud Condensation Nuclei’
Releasing shite that makes it rain more often
Which substances are often used for cloud seeding?
Ammonium Nitrate
Silver Iodide Pellets
How does urbanisation affect the drainage basin?
Impermeable surfaces
Reduced infiltration
Rising surface runoff + throughflow
Rapid increase in discharge
How does dam construction affect the drainage basin?
Increase surface water stores + evaporation
Reduces downstream discharge
How does deforestation affect the drainage basin?
Reduced evapotranspiration
Increased SRO
Shorter lag time
Declining surface storage
How does afforestation affect the drainage basin?
Reverses impacts of deforestation
Traps silt + lengthens lag time
How does increasing groundwater abstraction affect the drainage basin?
Reduced groundwater flow + lower water table
How does decreasing groundwater abstraction affect the drainage basin?
Reduced industrial activity/deforestation increases groundwater storage
Heightens risk of groundwater flooding
