Projected 21st Century Drought Condition in the South Saskatchewan River Watershed: A Case Study in the Canadian Prairies

In this study, a CMIP6 ensemble of 26 GCMs and SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios from CanDCS-U6 is used to project drought conditions in the South Saskatchewan River Watershed. The near-current period (2015-2030) and two future periods (2041-2060 and 2071-2100) are analyzed based on the Standardized Precipitation Evapotranspiration Index (SPEI) at 1-, 3-, 6-, 12-, and 24-month timescales. Projections indicate a shift in average SPEI values from above zero (no drought) in the base period (1951-1990) to more negative values in the future. Results show an increase in drought severity and frequency under climate change conditions. The percentage of time with no drought conditions is projected to decline from 55-70% in the base period to 25-45% by 2071-2100. Severe and extreme droughts, rare in the base period (below 4%), are projected to increase to up to 19% by 2071-2100. The area experiencing drought is expected to expand from 36-49% (for different SPEI timescales) in the base period to up to 76% by 2071-2100. Drought frequency is projected to be higher under SSP1-2.6 and less frequent under SSP2-4.5. Results showed that longer SPEI timescales are associated with higher drought occurrence rates and severity. The spatial pattern of drought is also projected to significantly change, with higher frequencies expected in the eastern parts of the watershed under climate change.