20.4. Empirical Methods

Try these first

1. 1.

   What is the Blaney-Criddle equation used for?

   Hint

   Look for the equation involving k, p, and T.

2. 2.

   Define the Thornthwaite method.

   Hint

   Focus on temperature and its importance in this context.

3. 3.

   What is the main purpose of empirical methods in estimating ET?

   • To provide direct measurements
   • To use observed data for estimations
   • To replace all measurement methods

   Hint

   Think about why we use formulas instead of measuring directly.

4. 4.

   True or False: The Hargreaves method is less accurate than the Thornthwaite method.

   • True
   • False

   Hint

   Recall the characteristics of both methods.

5. 5.

   A regional agricultural extension office is analyzing ET for potential irrigation planning. They have data showing the monthly average temperature as 30°C, the percentage of daylight in July as 60%, and a crop coefficient of 1.2. Use the Blaney-Criddle method to calculate ET.

   Hint

   Start with the equation definition and plug in the values carefully.

6. 6.

   A soil and climate research team is comparing the Thornthwaite and Hargreaves methods. They observe monthly temperatures averaging 20°C in winter. Discuss which of the two methods might give them a better estimate and why.

   Hint

   Think about the factors each method considers.