case studies

• Water cycle - Amazon

  • dense canopy intercepts up to 75% of rainfall
  • 25% of rain evaporates
  • some rain infiltrates and is stored temporarily on ground surface or flows overland to river channels
  • Amazon river discharges 15% of freshwater into Atlantic Ocean
  • 48% of water evaporated falls back as rain
  • 30% rainfall reaches the sea
  • 1/2 rainfall in some areas may never reach the ground as intercepted by forest
• impact of humans on water cycle - Amazon

  • deforestation reduces evapotranspiration, soil becomes compacted, more overland flow, soil erosion and higher flooding risk
  • water is abstracted for irrigation for agriculture
  • Amazon needs 80% of trees standing to continue the hydrological cycle and it is current at the tipping point of 81%