Enhancing drought monitoring in Southern Alberta: A comparative evaluation of drought indices for regional applicability

• Eight drought indices evaluated for Southern Alberta using streamflow and groundwater data • Indices grouped into three distinct categories based on performance characteristics • SPEI emerged as the most effective overall drought indicator • SPEI-9 showed strongest correlation with streamflow variability • SPEI-6 effectively captured groundwater level fluctuations • PDSI, EDI, and SPI offered complementary perspectives on drought conditions. Southern Alberta is highly prone to frequent and severe droughts, posing significant risks to its agricultural, socioeconomic, and ecological systems. This study evaluates the performance of eight meteorological drought indices; Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Self Calibrating Palmer Drought Severity Index (PDSI), Reconnaissance Drought Index (RDI), Effective Drought Index (EDI), China Z-index (CZI), Deciles Index (DI), and Percent of Normal Precipitation (PNP) across multiple timescales in terms of their drought monitoring skills. Using climate data from 37 meteorological stations, we evaluated each index’s ability to capture drought events and validated their performance against streamflow data, groundwater levels, and historical drought records from the Canadian Drought Monitor (CDM). The precipitation-based indices (SPI, CZI, DI, PNP) showed strong inter-correlation (> 0.90), while temperature-inclusive indices (SPEI and RDI) better aligned with hydrological responses. Among all, SPEI-9 showed the highest correlation with streamflow (0.50–0.69) and groundwater (0.42–0.47), particularly during summer and fall. The Cohen’s kappa analysis indicated substantial agreement (0.63–0.82) between SPEI, SPI, and RDI at longer timescales. Furthermore, SPEI and SPI effectively captured the major droughts in 2001-2002, 2009–2010 and 2015. While EDI and PDSI had weaker hydrological correlations (< 0.63), they provided valuable complementary insights. Overall, SPEI-9 is recommended as the most robust index for drought monitoring in Southern Alberta, with SPI, EDI, and PDSI offering additional support for comprehensive drought assessment.