poster - International Conference of Agricultural Engineering

Develop A Simple Economical Evaporation Pan
Mohamed A. Rashad 1 , and El-Sayed E. Omran 2 *
1 Agricultural Engineering Department, Faculty of Agriculture, Suez Canal University, Egypt.
2 Soil and Water Department, Faculty of Agriculture, Suez Canal University, Egypt.
* Corresponding author. E-mail: ee.omran@gmail.com - e.omran@scuegypt.edu.eg
Abstrat
The objective of the current study was “to develop a Simple Economical Evaporation Pan
(SEEP)”. The pan made using inexpensive materials which are simple, low cost, and can easily
be placed in several locations of an irrigated field. Four different pans sized very small (16cm),
small (32cm), medium (40cm) were compared to the standard large (57cm) pan. The pan
consists of a galvanized washtub with standard brass toilet bowl floats. Twelve pans (3
replicates for 4 diamter) were evaluated and tested to determine if the pans of the same size
responded similarly to each other, and how the variation was different between pan sizes. For
the test, 432 different readings were available over a period of time. The results show that pan
size 57 cm was the nearest from the standard class (A) in evaporation rate. But that not mean it
is the best one. The final decision for the best pan is based on the economical and many other
factors. The medium pan (M= Ф 40) did not respond exactly the same as the larger pan (L= Ф
57). However, the small pan (S= Ф 32) responded in a similar manner to the medium pan (M=
Ф 40) when compared to the large (L= Ф 57) pan. The very small pan (VS= Ф 16) representing
the evaporation that occurs from the large pan. Overall based on this study, the very small
sized pan (VS= Ф 16) offers a potentially less expensive alternative to irrigation scheduling. The
advantages of economical evaporation pan are facial in measurement and in transportation and
lower in cost of installation which make it easy for farmers to have evaporation pan and
calculate water requirement for all plant.
Key words: Economical Pan, Evaporation, Irrigation Scheduling.
1. Introduction
The current available methods for measuring rates of evaporation are limited. Unfortunately,
the three accurate direct methods of measurement available, i.e. weighing lysimeters, Bowen
ratio and eddy flux instrumentation, are unsuitable for monitoring evaporation as a routine direct
measurement at meteorological enclosures (Strangeways, 2001).
Field devices that integrate environmental effects and measure evaporation can be used to
schedule irrigation. These devices respond to water removal and water addition, like rainfall or
irrigation. Crop water use is commonly predicted using weather data to estimate reference
evapotrationspiration (ET 0 ). Evapotranspiration is not easy to measure. Specific devices and
accurate measurements of various physical parameters or the soil water balance in lysimeters
are required to determine evapotranspiration. The methods are often expensive, demanding in
terms of accuracy of measurement and can only be fully exploited by well-trained research
personnel. Although the methods are inappropriate for routine measurements, they remain
important for the evaluation of ET estimates obtained by more indirect methods.
The only two practical methods suitable for routine use in meteorological station networks are
measurements using evaporimeters and calculations based on other meteorological
measurements. The second is the approach, introduced by Penman in 1948 to estimate open
water evaporation (Penman, 1948) and extended by Monteith in 1965 to directly estimate
evaporation from vegetation covered surfaces (Monteith, 1965) which is now the method
recommended by the FAO to calculate reference crop evapotranspiration (Allen et al., 1998).
However, to apply the Penman–Monteith equation to natural vegetation or agricultural crop