River regimes

• River regime


  The annual variation in the discharge or flow of a river at a particular point, and is usually measured in cumecs.
• Simple regimes


  River experiences a period of seasonally high discharge followed by low discharge.
• Complex regimes


  • Large rivers cross several different relief and climatic zones
  • Experience different seasonal and climatic events
  • E.g. Mississippi, Ganges
• Much of the flow is not from immediate precipitation or run-off, but is supplied from groundwater between periods of rain. This can mask fluctuations in river flow caused by immediate precipitation as, for example in Britain, the River Kennet flows over chalk so it maintains its flow even at drier times due to the base flow being fed from chalk aquifers.
• River regimes diagram

  A) glacial

  B) Snowmelt

  C) Oceanic rainfall

  D) Monsoonal

  E) Simple

  F) Simple

  G) Complex

  H) Simple

  
• The regimes of the rivers Amazon, Yukon and Murray-Darling

  A) Amazon

  B) Yukon

  C) Murray-Darling

  
• River Yukon, Alaska, USA

  • High flow: Spring and summer
  • Low/no flow: Winter
  • Seasonable variability: Very large
  • Human influences: Relatively few - most of its landscape is wilderness
  • Major influences: Tundra and mountain climates, high summer temperatures, rainfall and snowmelt coincide
• Amazon River, Brazil


  • High flow: Wetter season
  • Low/no flow: Drier season
  • Seasonable variability: Moderate - fed by Andean rivers outside rainforest region
  • Human influences: Increasing - mostly deforestation
  • Major influences: Rainforest climate, seasonal precipitation, high evapotranspiration levels
• Murray-Darling River, Australia


  • High flow: Wet season
  • Low/no flow: Dry season
  • Seasonable variability: High
  • Human influences: Its waters a drawn by:
  • Australia's major cities
  • Farms for irrigation
  • Major influences: Seasonal sub-tropical climate, large rain shadow - long periods of drought