5.3b

• what are river regimes?

  the annual variations of river discharge
• what is river discharge?

  the volume of water that moves past a certain point in the river channel per second
• what affects river regimes?

  climate, geology and soils
• how does climate affect river regimes?

  • in glacial areas, an increase in temperature can create higher levels of meltwater, which increases river discharge, a drop in temperature will increase the amount of water stored in the cryosphere = decreases river discharge --> flow
  • hotter temps = more evapotranspiration --> output = intense short periods of rainfall more river discharge
• how does geology affect?

  • porous and permeable rocks allow more water to percolate, increasing baseflow and decreasing river discharge + act as aquifers - groundwater storage = flows into river slower = steady regime
  • impermeable rocks that lack joints cause greater levels of direct runoff and saturated overland flow
• how does soil type affect river regimes?

  some soil types retain water more easily than other soil types e.g. sandy soils have more air spaces between grains than clay soils = water can infiltrate quickly through sandy soils but may either go into groundwater storage in clay soils or rise to the surface in puddles
• describe the river regime of the Yukon river?

  location: Alaska and Canada

  • very low discharge in winter but a rapid rise in discharge in the early spring as rising temperatures cause rapid snowmelt
  • soils are prone to permafrost, which are impermeable all year round = overland flow will happen quickly once snowmelt occurs
• describe the river regime of the Amazon river?

  location: South America

  • gradual rise in discharge
  • the dry and wet season are not that different --> due to high levels of rainfall in most months which infiltrates the ground quickly due to thin soils and sedimentary rocks that dominate the Amazon basin
• describe the river regime of the Indus river?

  location: South and Central Asia

  • it's fed by snowmelt from the Himalayas in the spring
  • during June to September (monsoon months), the river is fed by regular precipitation
  • dry season from October to March = water deficit so lower discharge
  • drainage basin is largely consists of igneous and metamorphic rocks = less permeable so the river can quickly swell in volume during the monsoon season