poster - International Conference of Agricultural Engineering

surfaces requires information on their surface resistance to water loss. The use of the
Penman–Monteith equation in irrigation practice requires empirical coefficients to modify in
general to reduce but sometimes to increase the estimates of reference crop
evapotranspiration. It is of course the need for such empirical crop coefficients that is the major
criticism of the use of evaporimeters.
One meteorologically based device used for irrigation management is the evaporimeter, which
can be any evaporation measuring device such as an atmometer (Broner and Law, 1991) or
evaporation pan, whose data can be related to crop water use by applying crop coefficients as
are used to modify evapotranspiration models. The World Meteorological Organization (WMO)
has recommended that the evaporation pan be adopted as the standard instrument for crop
water use determination. The best known of the pans are the "Class A" evaporation pan and
the "Sunken Colorado Pan". The pan has proved its practical value and has been used
successfully to estimate reference evapotranspiration by observing the evaporation loss from a
water surface and applying empirical coefficients to relate pan evaporation to ET O (Stanhill,
2002, Thomas, et al., 2002). The problems involved in the use of Class A pan as expensive
and not easy movable were recognized.
According to our knowledge, no reports are available on using the economical and flexible
evaporation pan. The objective of this study is to develope a simple economical
evapotranspiration pan. The aim is to assess the feasibility of and also to provide guidelines for
setup and use of the evaporation pan for irrigation
2. Materials and Methods
Experiments were conducted at the soil and water department’s farm, Faculty of agriculture,
Suez Canal University. The main aim of this research is to propose evaporation pan and
calculate its K pan and compare it with the K pan of evaporation pan class A.
2.1. Pan Development Stages
Four galvanized steel pans with 16, 30, 39, and 57 cm diameter and 30 cm height were built-in.
The pans were from available materials in the market and at affordable prices. The pan
constructed with mesh covers and install unit to determine the increase and the decrease in the
water level (figure 1).
2.2. Field Experimental setup
The first field experiment was conducted from 15/04/2011 to 05/05/2011 and the second
experiment was conducted from 7/6/2011 to 21/6/2011. In order to calibrate the different pans
and determine k pan compared to k pan of the evaporation class A pan (120 cm diameter and 25
cm height) at the same condition, the following steps are considered (Figure 1). First, three of
the pans were distributed and put on wood base exept for the fourth size (16) which is installed
vertically at a djustable height of 150 cm above the soil. After that the horizontal of pans was
adjust by using water leveling apparatus to ensure the accuracy of prototype obtained. Second,
every three pans of the same type were distributed in one place to standardize the conditions
applicable to them. Third, the evaporation class A pan was Put with different pans to compare it
with the different pans. Finally, wind speed was measured by Anemomete (accuracy 0.1 km
/hr) for used in equations to calculate the K pan . Also, the temperature and humidity were
measured by digital temperature and humidity device at the time of sunrise and noon. The
water level reading in pans was started in same time from first day until last day.