Drainage Basin

  • Created by: Ali Bland
  • Created on: 18-03-15 13:29
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  • Drainage Basin
    • This is an area of land drained by a river and its tributaries
    • Its an open system with inputs,outputs, stores, flows/transfers and outputs
    • A drainage basin acts as a largely closed system because it has a very definite outer edge or boundary
    • There is little, is any transfer of water between drainage bains
    • The movement of water within the drainage basin is illustrated by the drainage basin hydrological cycle
  • Drainage Basin Hydrological Cycle
    • Precipitation
      • All forms of moisture that reach the Earth’s surface e.g. rain, snow, sleet and hail
    • Evapotranspiration
      • the loss of water from a drainage basin into the atmosphere from the leaves of plants + loss from evaporation
    • Interception
      • This is when precipitation lands on buildings, vegetation and concrete before it reaches the soil
    • Depression Storage
      • When water is stored temporarily on the ground surface in the form of puddles
    • Baseflow, or groundwater flow
      • The very flow transfer of water through rocks
    • River Channel
      • The river forms the "exit" for water transferred through the drainage basin
    • Percolation
      • The deeper transfer of water into permeable rock - those with joints or are porous
    • Throughflow
      • The movement of water downslope within the soil layer
    • Infiltration
      • The downward movement of water into the soil surface
    • Overland Flow
      • A rapid form of water transfer over the surface of the ground
  • The Water Balance
    • This is the balance between inputs and outputs in a drainage basin
    • This is expressed as P=O+E+/-S
      • P= Precipitation
      • O=Total Runoff
      • E=Evapotranspiration
      • S=Storage
    • When the inputs and outputs are balanced it is said to be a dynamic equilibrium


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