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poster - International Conference of Agricultural Engineering

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climate. Therefore a special coefficient is used (K pan ) to relate one to the other. ET o and E pan<br />

are required to calculate (K pan ) coefficients. K pan values depend upon the location <strong>of</strong> the<br />

evaporation pan, the average daily relative humidity, the average daily wind speed, and the<br />

type <strong>of</strong> area surrounding the pan. The pan evaporation rate (and thus the value <strong>of</strong> K pan ) is<br />

different if the pan is surrounded by bare soil as opposed to a vegetated surface.<br />

ET o = K pan × E pan<br />

ET o : reference crop evapotranspiration, K pan : pan coefficient, E pan : pan evaporation<br />

If the water depth in the pan drops too much (due to lack <strong>of</strong> rain), water is added and the water<br />

depth is measured before and after the water is added. If the water level rises too much (due to<br />

rain) water is taken out <strong>of</strong> the pan and the water depth before and after is measured.<br />

3. Results and Discussion<br />

3.1 Overall Daily Reading <strong>of</strong> Atmosphere Data<br />

Daily averaged meteorological data recorded in the study field (Ismailia city) from (15/4) to (5/5)<br />

are shown in Table 1. The rate <strong>of</strong> evaporation is the amount <strong>of</strong> water evaporated over a given<br />

period <strong>of</strong> time. On open bodies <strong>of</strong> water, the rate is affected by several ground and atmospheric<br />

factors <strong>of</strong> which the main ones are: Solar radiation, Relative humidity, Winds, temperature. It is<br />

important to note that the effects <strong>of</strong> ground and atmospheric conditions on large water bodies<br />

can be different to the effects on an evaporation pan.<br />

TABLE 1: Meteorological data recorded during the experiment: air temperature, relative<br />

humidity (RH), and average wind speed.<br />

Day Julian Day<br />

Temperature<br />

Hummidity<br />

MAX TEMP MIN TEMP MAX RH MIN RH<br />

AVG Wind SPEED<br />

15 April 106 28.6 12.0 83 35 9.5<br />

16 April 107 29.4 14.4 85 38 7.9<br />

17 April 108 30.7 12.5 84 28 6.3<br />

18 April 109 34.0 14.4 71 23 7.3<br />

19 April 110 36.5 16.8 69 22 8.9<br />

20 April 111 35.3 17.0 65 26 6.0<br />

21 April 112 29.1 15.9 80 38 8.0<br />

22 April 113 22.6 13.9 81 48 9.2<br />

23 April 114 26.0 13.0 88 35 7.0<br />

24 April 115 28.1 12.9 80 35 9.3<br />

25 April 116 30.9 14.0 80 32 9.2<br />

26 April 117 31.0 14.8 82 35 7.2<br />

27 April 118 34.3 14.8 80 25 6.1<br />

28 April 119 26.8 14.7 85 44 9.1<br />

29 April 120 28.1 14.9 87 39 6.4<br />

30 April 121 28.8 15.2 81 36 7.2<br />

1 May 122 27.4 13.5 83 35 6.6<br />

2 May 123 26.0 12.4 88 37 6.4<br />

3 May 124 28.5 12.9 83 32 6.3<br />

4 May 125 29.9 13.9 84 31 6.2<br />

5 May 126 30.8 14.4 84 30 6.2<br />

7 June 159 34.9 14.7 86 33 8.3<br />

8 June 160 29.3 14.6 87 46 6.9<br />

9 June 161 30.5 12.5 85 38 6.5<br />

10 June 162 33.8 13.1 78 30 8.4<br />

11 June 163 35.3 14.9 79 28 6.8<br />

12 June 164 31.3 15.8 86 43 7.4<br />

13 June 165 32.5 16.1 86 40 6.3<br />

14 June 166 32.7 14.9 85 35 6.3<br />

15 June 167 31.5 14.4 84 37 7.1<br />

16 June 168 34.8 18.0 81 40 7.4<br />

17 June 169 36.8 19.6 83 37 8.0<br />

18 June 170 36.5 17.2 82 39 7.9<br />

19 June 171 36.1 15.0 86 37 9.1<br />

20 June 172 40.1 15.0 73 27 8.9<br />

21 June 173 42.4 14.5 70 22 6.2

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