5.2b

• what are the physical factors that affect the inputs, flows and outputs of drainage basins?

  climate

  soil

  vegetation

  geology

  relief
• how does climate affect the inputs in a drainage basin?

  affects the type and amount of precipitation - intense storms generate more precipitation and greater peak discharges than light rain showers = flows like runoff and stores like groundwater to increase in size

  higher temperatures = more evaporation which can cause convectional precipitation (short periods of intense rainfall)
• how can climate affect flows in drainage basins?

  • during the winter, temperatures may drop below 0C, causing water to freeze, reducing the size of flows as more water is stored in the cryosphere 
  • when temperatures increase again, flows through drainage basins can be much larger as the ice melts  
• how can climate affect the outputs in drainage basins?

  • higher temperatures = more evaporation
  • climate affects which vegetation can grow there, so affects how much interception and evapotranspiration occurs
• how can soil affect?

  • soil type, soil structure and the level of saturation affects infiltration rates e.g. larger air spaces in sandy soils allow more infiltration than clay soils
  • throughflow is faster through openings such as cracks in the soil or animal burrows
  • soil type can influence the type of vegetation that can grow there and therefore the amount of interception and evapotranspiration that occurs
• how does vegetation affect?

  • vegetation intercepts precipitation and slows its movement into the river channel (slows the rate of overland flow) interception is highest when there's lots of vegetation and deciduous trees that have their leaves
  • the more vegetation there is, the more water is lost through evapotranspiration before it reaches the river channel, reducing overland flow and peak discharge
• how does geology affect?

  • water flows slowly through most rocks, but rocks that are highly permeable e.g. sandstone or rocks with lots of joints that allow water to percolate into them e.g. limestone can cause faster groundwater flow
  • impermeable rocks stop water percolating into tem, which means there are higher rates of direct runoff
• how does relief affect?

  • the steeper the gradient of the landscape, the less infiltration occurs so direct runoff and throughflow occur faster so surface stores have a shorter residence time in steeper areas
  • higher altitudes experience more precipitation