Physical

• types of drought

  • meteorological: degree of dryness compared to what is considered normal precipitation levels for that area, climate and season
  • Agricultural: insufficient water for crops
  • hydrological: DB exp shortfalls eg reduced streamflow or increase in river flow into reservoirs
  • socio-economic(famine): demand for water to be used for social and economic purposes eg crop irrigation
• Physcial causes of drought(PCOD)

  • ENSO- EL Nino

  1. evert 3-5 years
  2. winds weaken across south pacific ocean and reverse direction
  3. warm water to South American coastline= lower air pressure= large increases in rainfall= risk of flooding
  4. australasia= cooler then normal ocean temp = higher pressure= little rainfall= risk of drought
• PCOD

  • La Niña
  • lo air pressurge descends on SE Asia and australia= increased rainfall and risk of flooding
  • South America= high air pressure= reduced rainfall= likelihood of drought
• PCOD

  short term precipitaion deficit

  • when cycle creates clouds= interrupted
  • may be exp in areas that are used to low air pressure systems and have a change of weather front to exp high pressure air system
  • cool sinking air in high pressure systems doesnt have ability to form clouds= no precipitation
• Human causes of drought(HCOD)

  Brazil

  • 2014-15 industries farmers and domestic users used groundwater until rivers ran low
  • poor/rural suffered bc only had access to groundwater
• Causes of over abstraction HCOD

  • gov introduced charge for drilling wells US$35000-100000
  • started drilling illegally bc couldn’t affect the charge= water abstracted was no monitored
  • offiicial records of wells only present 1/3 of total as 70% were illegally drilled
• Problems with over abstraction

  • illegal wells=shallower=not percolated deep into bedrock= less filtered= may contain industrial and agricultural pollutants w/ higher levels of bacteria
  • increase in poor sanitation and water bourne disease