Drainage basin hydrological cycle

• hydrological cycle in a drainage basin

  inputs= precipitation

  • orographic = air masses rise over mountains -> condense and rain
  • frontal = 2 air masses meet at area of low pressure = rain
  • conventional = water turning to water vapour bc of solar radiation
• hydrological cycle in drainage basin

  outputs

  • evaporation = turns to water vapour and leaves
  • transpiration = water leaves plants thro holes in leaves
  • channel flow = volume of water flowing in a river channel
• hydrological cycle in a drainage basin

  main flows

  • interception = plants capture precipitation in leaves
  • infiltration = precipitation enters soil
  • direct runoff = water from precipitation/ snowmelt flows across grounds surface bc surface is impermeable
• hydrological cycle in drainage basin

  other flows

  • saturated overland flow = ground full of water -> runoff
  • throughflow = horizontal flow of water thro soil/rock layers
  • percolation = vertical flow of water between soil and rock layers
  • groundwater flow = flow of water horizontally once it has reached water table
• Physical factors affecting drainage basin

  soil type

  • impermeable soil stops infiltration -> surface saturation -> increased surface runoff
  • permeable allows infiltration and percolation -> groundwater to recharge
• physical factors affecting drainage basin

  vegetation cover

  • high coverage = interception and evapotranspiration increases but surface runoff decreases
• physical factors affecting drainage basin

  relief of land

  • steeper = faster surface runoff and shorter times for water storage
• physical factors affecting drainage basin

  rock type

  • impermeable = stops infiltration of water into ground -> ground saturates -> surface runoff and increase flows in rivers
  • permeable allows for infiltration and percolation
• physical factors affecting drainage basin

  climate

  • cold = precipitation falls as snow -> water stored and held back until thawed
  • may reduce channel flow in winter and increase during the spring and summer due to glacial melt water
• Human factors affecting drainage basin ( HFADB)

  reservoirs

  • man made -> disrupt natural water flow by delaying flow and increasing water lost from evaporation
  • damns = reduce water flow further downstream = loss of vegetation
  • vegetation grows on reservoir surface = increase in evapotranspiration -> increase in salinity of water
• HFADB

  urbanistaion

  • change of land, resulting in moving away from natural environment to towns and cities
  • leads to large number of impermeable surfaces eg tarmac = reduces infiltration and increases surface runoff
• HFADB

  over abstraction= volume of water removed is greater then volume replenished

  • abstraction=processes humans remove water from underground stores eg aquifers
  • leads to rivers drying p during periods of low rainfall
• HFADB

  deforestation

  • removal of trees
  • reduces interception -> rain strikes soil directly = soil compaction -> reduces infiltration and increase surface runoff = more soil erosion and flooding