Question

Line up the following methods for ET\(_{0}\) estimation according to year of development, earliest to latest.
A. Blaney and Criddle
B. Radiation
C. Penman-Monteith
D. Modified Penman
Choose the correct answer from the options given below:

• A. A, C, B, D
• B. A, D, C, B
• C. A, D, B, C
• D. C, B, D, A

Hint:

The evolution of ET models went from simple to complex: Temperature-based (Blaney-Criddle) \(\rightarrow\) Combination of energy and aerodynamics (Penman) \(\rightarrow\) Simpler energy-based (Radiation) \(\rightarrow\) Refined combination with plant physiology (Penman-Monteith).

Answer 1

The Correct Option is C

Step 1: Recall the historical development of evapotranspiration (ET) estimation methods.
The methods evolved from simple empirical formulas based on temperature to more complex models incorporating radiation, wind, and plant physiology.
Step 2: Place each method in its historical context.
- A. Blaney and Criddle (1950): This is one of the earliest and simplest empirical methods, based primarily on temperature and daylight hours.
- D. Modified Penman (1963 by FAO, based on Penman 1948): Howard Penman's original combination method (1948) was a major breakthrough. The "Modified Penman" generally refers to the FAO-24 version, which adjusted coefficients and became a widely used standard. It came after Blaney-Criddle but before the widespread adoption of specific radiation methods or the Penman-Monteith refinement.
- B. Radiation (e.g., Jensen-Haise 1963, Priestley-Taylor 1972): Methods based primarily on solar radiation as the main driver of ET were developed as an alternative to the more data-intensive Penman method. They generally post-date the original Penman work.
- C. Penman-Monteith (1965): This is a further refinement of the Penman equation, incorporating a surface resistance term to better account for the physiological control of transpiration by plants. It is now considered the global standard (FAO-56 Penman-Monteith).
The chronological sequence is: Blaney and Criddle \(\rightarrow\) Modified Penman \(\rightarrow\) Radiation \(\rightarrow\) Penman-Monteith. This corresponds to A, D, B, C.