Evolutional characteristics of hydro-meteorological drought studied using standardized indices and wavelet analysis

Abstract

The study presents a more recent historical analysis of hydro-meteorological droughts in the Olifants Basin, South Africa from 1980 to 2013 using the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI) and the Streamflow Drought Index (SDI). Time series of SPI, SPEI and SDI were analyzed for drought intensity and duration using wavelet analysis. Results indicate different periodicity and temporal variability of drought with significant meteorological drought incidence in 1991–2004 within the 2–8-year band and hydrological drought in 1996–2004 within the 3–5-year band. Spearman correlation analysis revealed a significant correlation (p < 0.01) between SPI and SPEI irrespective of the timescale. However, the strongest correlation occurred at the same timescale for SPI and SPEI: 3-month timescale (r = 0.904, p < 0.01), 6-month timescale (r = 0.936, p < 0.01), 9-month timescale (r = 0.946, p < 0.01) and 12-month timescale (r = 0.947, p < 0.01). A significant relation also existed between SDI and SPI (r = 0.731, p < 0.01) as well as between SDI and SPEI (r = 0.631, p < 0.01). Findings further indicate varying degrees of drought ranging from near normal to extremely dry conditions during 1980–2013. It is expected that strategies and policy actions on drought factor in the recurring nature of droughts so as to minimize the negative impact on water resources and other human–hydro-ecological systems.