booklet 4 - water balance and regimes

• What is river discharge?

  Volume of water flowing through a river
• How is river discharge expressed?

  In cumecs (cubic metres per second)
• What is the formula for calculating discharge?

  Discharge = cross sectional area x velocity
• What causes variations in run-off?

  Size of drainage basin, geology, rainfall
• Why is the type and intensity of precipitation important in river discharge?

  Intense rainfall increases runoff into rivers
• How does drizzle affect runoff?

  It is held on trees and grass, evaporates
• What happens to runoff when snow melts?

  Runoff values might be high after melting
• What is a river regime?

  Variability in a river's discharge throughout the year
• What factors influence a river regime?

  Precipitation, temperature, evapotranspiration
• What are the characteristics of the River Avon regime?

  • Flow rises in autumn
  • Late summer minimum
  • Increased evapotranspiration in summer
• What are the characteristics of the Mohawk River regime?

  • Spring maximum due to snowmelt
  • Increased rain from cyclones
  • Low temperatures lead to frozen conditions
• What are the characteristics of the Nile River regime?

  • No discharge from Nov to June
  • Flow increases from Blue Nile
  • Steady flow from White Nile
• How does heavy rain affect runoff?

  It causes greater runoff into rivers
• How does snow affect runoff?

  It has a longer lag time before runoff
• What is the effect of impermeable soils on runoff?

  They likely cause more runoff due to less infiltration
• How does rock type influence runoff?

  Impermeable rock reduces percolation and increases runoff
• What human activities can affect runoff?

  Agriculture, urbanization, deforestation
• How do drainage systems affect river regimes?

  They control water flow and regime variability
• What is the impact of deforestation on runoff?

  It leads to less interception and more runoff