Estimation of Future Crop Water Requirements for 2020 and 2050, Using CROPWAT

The objective of this study was to determine the impacts of potential climate change on daily and total crop water requirements (CWR) of peaches in Southern Ontario using CROPWAT in conjunction with the climate scenarios derived from SDSM. Baseline climate is based on the 30 year-period, 1971-2000 of the mean monthly normals, and two time periods in the future centered on the decades of 2020s (2010-2039) and 2050s (2040-2069). The climate parameters of temperature, precipitation, relative humidity, sunshine duration and wind speed were downscaled using the SDSM (version 3.1) method. To determine the future crop water requirements (CWR), the CROPWAT model (FAO, 1992) was used to simulate the daily and the season total CWR and irrigation requirements for the present and the future decades. Results compared to the base climate show an increase in crop water requirements of 6.0 % (39 mm) per season using the SDSM-CGCM1 model for 2020s and 3.0% (20 mm) per season using both the SDSM-HADCM3 A2 & B2 models for 2020s. About 8 % (56 mm) increase in using the SDSM-CGCM1 and HADMC3 A2 models for 2050s, and 7.0 % (43 mm) per season. However, the irrigation requirements decreased, compared to the current situation, by 6.0 % (18 mm) (assuming 90% irrigation efficiency) using the SDSM-CGCM1 for 2020s and by 27% (81 mm) for both SDSM-HADCM3 A2 & B2 models for 2020s. While in 2050s, a decrease of 2.71% (8 mm), 21% (64 mm) and 6% (59 mm) using the SDSM-CGCM1, SDSM-HADCM3 A2 and SDSM-HADCM3 B2, respectively for 2050s.