CGP Drainage Basins

• Drainage Basins


  Natural Systems
• Drainage Basins


  Open, local hydrological cycles
• Drainage Basin


  • Area surrounding a river where rain falling on the land flows into that river
  • Also called the river's catchment basin
• Watershed


  • The boundary of a drainage basin, any precipitation falling beyond the watershed enters a different drainage basin
• Drainage Basins


  • Open systems with inputs and outputs
• Inputs and Outputs of Drainage Basins

  1. Water comes in as precipitation

  2. Water leaves via evaporation, transpiration and river discharge
• Stores of Water in Drainage Basins

  • Interception storage
  • Vegetation storage
  • Surface storage
  • Soil storage
  • Groundwater storage
  • Channel storage
• Flows of Water in Drainage Basins

  1. Infiltration

  2. Overland flow

  3. Throughfall

  4. Stemflow

  5. Throughflow

  6. Percolation

  7. Groundwater flow

  8. Baseflow

  9. Interflow

  10. Channel flow
• Evapotranspiration


  The process of evaporation and transpiration together
• Potential Evapotranspiration (PET)


  The amount of water that could be lost by evapotranspiration
• Actual Evapotranspiration


  What actually happens, e.g. in a desert PET is high but actual transpiration is low due to lack of moisture
• Water Balance

  1. Calculated from inputs (precipitation) and outputs (channel discharge and evapotranspiration)

  2. Affects how much water is stored in the basin

  3. Shows seasonal patterns - wet seasons have a surplus, dry seasons have a deficit