Simulation of Climate Change Impacts on Crop Yield in the Saskatchewan Grain Belt Using an Improved SWAT Model

Climate change has a potentially significant influence on agricultural production in southern Saskatchewan. Crop yields are susceptible to weather patterns and seasonal fluctuations in this sub-humid region owing to the predominance of rain-fed farming practices. A modified Soil and Water Assessment Tool (SWAT-M) and the output from 10 high-resolution (0.22 degrees) regional climate models (RCMs) were used to develop simulations of spring wheat and rain-fed canola in 296 rural municipalities (RM) for a historical baseline period (1975-2004) and three 30-year future periods: near (2010-2039), middle (2040-2069), and far (2070-2099). We combined SWAT-M with the S-curve method to adjust yield to the original drought stress in the source code and evaluated eight indices of extreme precipitation and temperature. Results of calibration and validation suggest that the simulated crop yields generally agree with observed data. Crop yield showed lesser performance compared with streamflow and soil water content (SWC) along with percent bias, ranging from -9.6% to -14.8%, while streamflow calibration ranges from -5.3% to -7.7%. The multi-model ensemble median showed increasing radiative forcing in the temperature and precipitation indices, such that the RCM-projected weather indices were found to be warmer and wetter than those estimated using regional historical data. The results of simulating canola and spring wheat indicate an increase in crop yield of 17% and 9.7% in the near future, 28.2% and 15.6% in the middle future, and 44.7% and 32% in the far future, respectively. Although, there has been an increase in the median wheat and canola yields, a significant reduction in the annual production is observed. This decline in yield amounts to around 1000 kg/ha and is anticipated to occur in the near and middle future. This trend is quite pronounced in the extreme south and southwest regions. Overall, this innovative research framework, along with the region-specific model outcomes in the form of crop yield projections, will aid in the formulation of future agricultural policies aimed at promoting effective climate adaptation strategies.