Multiple drought indices for agricultural drought risk assessment on the Canadian prairies

A multi-index drought (MID) model was developed to combine the strengths of various drought indices for agricultural drought risk assessment on the Canadian prairies, as related to spring wheat crop yield. The model automatically selects and combines optimum drought indices derived from the preceding and current months as they become available to better match the conditions (both spatially and temporally) where they work well. The cross-validation results showed that (1) the prediction accuracy of the MID model is better than (or occasionally equal to) using any single drought index for all modelling stages, (2) drought indices derived from the recharge period are useful for early drought risk detection, (3) model prediction accuracy improved as the growing season progressed with the most accurate assessments at the beginning of August, and (4) the model performed best in the more arid locations in the southern prairies, which tend to have a more variable precipitation regime. The model assessment results provide the spatial intensity distribution of possible drought progression and recession before and during the growing season, and can be used with complementary information in agricultural drought risk management and mitigation strategies