Investigating Drought Duration-Severity-Intensity Characteristics Using the Standardized Precipitation-Evapotranspiration Index: Case Studies in Drought-Prone Southeast Queensland

Drought characterization is crucial for identifying impacts on irrigation, agriculture, hydrologic engineering, and water resources management. This case study demonstrates the scientific relevance of the standardized precipitation-evapotranspiration index (SPEI) as a robust drought metric that incorporates influence of supply-demand balance. Using long-term data, the SPEI was calculated at multiple timescales to identify historical water deficit periods in selected drought-prone case study regions in southeast Queensland, Australia. The drought duration (D; number of months with continuously negative SPEI representing below average water resources), severity (S; accumulated negative SPEI in a drought-identified period), intensity (I; minimum SPEI), and return periods were enumerated for iconic dry events over multiple (1-, 3-, 6-, 9-, 12-, and 24-month) timescales. The SPEI was evaluated with corresponding drought indicators (precipitation and soil moisture) and climatological Rainfall Anomaly Index to yield drought severity information from a meteorological perspective. The results showed disparities in duration, severity, and intensity (D–S–I) of different droughts among the case study regions; reaffirming the significance of SPEI for regional drought impact assessment. Accordingly, this case study advocates SPEI as a convenient metric for detecting drought onsets and terminations, including drought ranking and recurrence evaluations that are vital statistics in hydrologic engineering.