Geography 327      Hydrology


"all the processes by which water in the liquid or solid phase at or near the earth's land surface becomes atmospheric water vapour" (evaporation, transpiration, sublimation)


Controls on evaporation rate

Universal factors

  1. energy
  2. temperature
  3. humidity
  4. wind

Additional controls on evaporation from water bodies

  1. water quality
  2. depth of the water body
  3. area of water body

Additional factors controlling the rate of evaporation from soil

  1. soil moisture content
  2. soil texture
  3. depth to water table
    coarse sand 35 cm
    fine sand 70 cm
    heavy loam 85 cm

  4. soil colour
  5. vegetation

Determining evaporation

theoretical (physically-based) approaches

  1. turbulent (mass) transfer
  2. energy balance approach

direct measurement

  1. lake water balance:

  2. atmometer
  3. lysimeter


"evaporation ... from the vascular system of plants"

Potential evapotranspiration

Relative importance of evapotranspiration

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