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S. Ouda
Shahidian et al. [32] as follows:
ET(P-M) = a + b ∗ ET(H-S)
(1)
Thus, we used BISm model [17] to calculate ET(P-M) and ET(H-S) using 2016
weather data. The agro-climatic zones developed by Ouda and Noreldin [33] were
used to ease calculations. Figure 1 illustrated these five agro-climatic zones.
An equation for each agro-climatic zone was developed, where different (a) and
(b) values were estimated. The quality of the fit between ET(P-M) and ET(H-S) was
presented in terms of the coefficient of determination (R
2 ), which is the ratio of the
explained variance to the total variance and through calculation of root mean square
error per observation (RMSE/obs), which gives the standard deviation of the model
prediction error per observation [34].
Thus, the above-developed equations were used to project ETo value similar to
ET(P-M) using the data of RCP6.0 scenario and apply it to BISm model [17] in 2030.
The projected value of ET(P-M) was then used in BISm model [17] to calculate Kc
values for the selected crops in each of the five agro-climatic zones of Egypt.
Fig. 1 Map of agro-climatic zones of Egypt. Source Ouda and Noreldin [33]