Evaluation of some empirical methods of estimating potential evapo- transportation is a well-researched topic, it can be used as a guide or framework for your Academic Research.
A comparison of 4 empirical methods of calculating potential evapotranspiration (PE) using climatic data for the estimation of the length of the growing season from rainfall – potential evapotranspiration model was carried out using 15 years of estimates recorded in Shaki, Southwestern Nigeria. The length of the growing season estimated from the 4 empirical methods of PE was related to the moisture
requirements of some selected tropical crops. Data were analyzed by one – way ANOVA taking each yearly mean as the average of the 15 years (1991 – 2005) for the station. Results show that the methods
varied greatly in their ability to define the magnitude and variability of the length of the growing season. The original Penman and the modified Penman of McCulloch models showed no significant difference
in their use for the determination of the length of the growing season. However, the Thornthwaite, the Priestly, and Taylor showed differences in the estimates of the length of the growing season. Priestly and Taylor gave the least estimate of the length of the growing season. The relative reliability of each method in terms of accuracy of both measured and extrapolated meteorological data utilized was also discussed.
In the wet and dry climate, the length of the growing season
is mainly controlled by the availability of water. However,
depending on rainfall in the determination of the length of
the growing season of agricultural crops could be of great
risk in farming operations. This is because the difference
in the soil with regards to the storage capacity and
availability of soil moisture strongly influence agricultural
potentialities than the volume of rainfall. This may be due
to the fact that rainfall might runoff without entering the
soil, particularly on hilly terrain. Hence, the balance
between water within the root zone of the soil caused by
rainfall and the water loss resulting from evapotranspiration is of fundamental significance in the determination of
the length of the growing season of agricultural crops in the area.
Therefore, rainfall (P) and potential evapotranspiration
(PE) are pre-requisite parameters in the determination of
the growing season. However, the difficulty encountered in
using the rainfall and PE model lies mainly in the inability
to properly measure or estimate the 2 components. It is
observed that while precipitation is measured in
numerous places in Nigeria, the accurate field
measurement of PE is not only rare but difficult (Bello,
1997). In particular, class A evaporation pan, which has
been widely used in Nigeria for estimation of evaporation,
is unreliable (Olaniran, 1983).