*3.3. Analysis of Reference Crop Evapotranspiration*

This study estimated reference crop evapotranspiration (ET0) using the Penman-Montieth equation. Projected changes in ET0 were calculated as the difference between the

average monthly and annual ET0 for RCP 4.5 and RCP 8.5 relative to baseline (1976–2005). Results from the calculation show an increasing trend in total annual ET0 of 770.9 mm, 810.0 mm, and 817.8 mm for RCP 4.5 and 778.0 mm, 829.3 mm, and 904.5 mm for RCP 8.5 for the early-term, mid-term, and end-term relative to 729.1 mm of baseline climate (1976–2005). The intra-annual ET0 variation indicated a higher increase in the months of September, August, and October while April had the smallest increase for both climate change scenarios as illustrated in Figure 5. The increase in ET0 aligned with the increasing trend in temperature, implying that a change in temperature would have a significant impact on the amount of soil evaporation and crop transpiration.

**Figure 5.** Predicted changes in the reference evapotranspiration for RCP 4.5 and RCP 8.5 relative to baseline climate (1976–2006) for the period (**a**) 2010–2039, (**b**) 2040–2069, and (**c**) 2070–2099.
