poster - International Conference of Agricultural Engineering

3.2 Description of the Tested Pans
The variability in pan level readings within a particular treatment was analyzed using the
coefficient of variation (Table 2). The expectation is that the smaller pans would respond to
evaporation rates (change in water level) in a similar manner to the larger pans. The analysis
was made to determine if the pans of the same size and same screen material 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 that did not include a refill of a pan or a
significant rainfall event (where a pan overflowed through the drain hole).
TABLE 2: Description of pans that were tested.
Label– diameter, cm Description SD Mean Variance CV**
VS- 16 Very Small 2.3553 8.75 5.547 26.91
S-32 Small 0.900029 5.63 0.810 15.97
M-40 Medium 0.918361 6.08 0.843 15.11
L-57 Large 1.008692 6.48 1.017 15.58
Class A Pan 1.150611 7.01 1.324 16.42
**CV is the coefficient of variation calculated for the three replications of each treatment based on the average of the individual
reading CVs (SD/Mean difference in water level for the three replications) over the entire period of study.
3.3 Relation between Kpan and Epan and different pans dimensions
Figure 2 shows the E pan , ET O and K pan results. At the same period, the water level of four
different pans was measured by using the schematic prsented in figure (1). Moerover,
measuring water level in pan class (A) was prsented.
These different results in K pan and E pan were according to different between pans in dimensions and
materials and zero point from pan to pan adding to different in daily atmosphere data. ET O is
constant to all pans in day. But, it's variable from day to day according to the different in daily
atmosphere data that entered in crop water program.
3.4 Response of the smaller pans in comparison to the larger pan
To get an idea of the overall performance of developed pan, the relashionship and linear
correlation line for the average wáter loss or gain between the large pan and the small pan
were plotted together. The results show that there are a linear correlation between the small
(Ф 16cm) and large pan (Ф 57cm). At last from the resulting data, pan Ф 57cm was the nearest
from the standard class (A) in evaporation rate. But that it is not mean Ф57 cm is the best. K pan
(Ф16- Ф32- Ф40) has no large difference between them. But the best pan limits according to
price and many parameters, so Ф16cm is the most simple economical evaporation pan. The
very small pan did a better job of representing the evaporation that occurs from the large pan.
The pan is suitable for the small holder farms (i.e., window screen and a short rod length). The
very small pan may be a reasonable alternative. Statistical results did not show any significant
differences (based on P