- 2075 Chaitra · 3 marks
Actual versus potential evapotranspiration
Short answer
PET is maximum evapotranspiration with unlimited water, controlled by climate. AET is actual loss limited by soil moisture, crop type, and stage; AET ≤ PET, equal only when soil moisture is adequate.
Differentiate actual and potential evapotranspirations.
| Point | Potential evapotranspiration (PET) | Actual evapotranspiration (AET) |
|---|---|---|
| Meaning | Evapotranspiration from a large area of short green crop fully covering the ground, with unlimited water supply | Actual amount of water lost by evaporation and transpiration under existing soil moisture |
| Water supply | Not limited | Limited by soil moisture |
| Controlled by | Climate (radiation, temperature, humidity, wind) | Climate plus soil moisture, crop type and stage |
| Value | Maximum possible rate | Equal to or less than PET |
| Relation | AET = PET when soil moisture is adequate | AET < PET in dry soil (AET = k × PET, k < 1) |
| Use | Crop water requirement, irrigation planning | Water balance, actual catchment losses |
✓ Answer checked by Claude Sonnet 5.5
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