5.2C Human factors affecting the drainage basin

• How humans affect the drainage basin level:

  • deforestation
  • changing land-use
  • abstraction
  • reservoirs
• How deforestation affects the drainage basin:

  • The felling and clearance of trees reduces interception and infiltration rates
  • It increases surface run off
  • It reduces evapotranspiration which reduces precipitation
• How changing land-use affects the drainage basin:

  • Urban surfaces of tarmac and concrete are impermeable so reduce infiltration and increase surface run off
  • Drainage systems move water to rivers more rapidly increasing the risk of flooding
  • Agriculture reduces the amount of large vegetation decreasing interception and increasing surface run off
  • Livestock farming can leading to compaction of the soil reducing infiltration
• How abstraction can affect the drainage basin:

  • Over-abstraction leads to reduced flow in rivers and reduces the amount of groundwater
• How reservoirs affect the drainage basin:

  • The construction of dams and reservoirs reduce water flow downstream
  • Increases evaporation as there is greater surface area of water