21. Evapotranspiration Equations: Penman and Blaney & Criddle Methods

Try these first

1. 1.

   What are the two main components of evapotranspiration?

   Hint

   Think of how water leaves the soil and plants.

2. 2.

   Define Potential Evapotranspiration.

   Hint

   What happens when there is plenty of water?

3. 3.

   What does ET stand for?

   Hint

   It's all about water leaving the soil and plants.

4. 4.

   The Blaney & Criddle Method is best used in areas with high climatic variability.

   • True
   • False

   Hint

   Reflect on where simple methods work best.

5. 5.

   Calculate the PET using the Penman Method with given values: Rn = 20 MJ/m²/day, Δ = 0.1 kPa/°C, γ = 0.065 kPa/°C, f(u) = 0.5, es = 2.3 kPa, ea = 1.5 kPa.

   Hint

   Break down the calculations piece by piece for accuracy.

6. 6.

   Discuss how the choice between these two methods might change in a region that has seasonal variations in climate.

   Hint

   Consider the trade-offs between simplicity and accuracy.