Projected Drought Prevalence in Malawi’s Lufilya Catchment: A Study Using Regional Climate Models and the SPI Method

Abstract

Droughts are caused either by a deficiency in precipitation compared to normal levels or by excessive evapotranspiration exceeding long-term averages. Therefore, assessing future drought prevalence based on projected climatic variables is essential for effective drought preparedness. In this study, an ensemble of three Regional Climate Models (REMO2009, RCA4, and CCLM4-8-17) was used for Representative Concentration Pathways (RCP 4.5 and RCP 8.5), covering two future time periods (2025–2069 and 2070–2100). The quantile distribution mapping technique was employed to bias-correct the RCMs. The ensemble of RCMs projected an increase in rainfall, ranging from 40% to 85% under both RCP 8.5 and RCP 4.5. Both RCPs indicated an increase in daily average temperatures. RCP 4.5 projects an increase in average daily temperature by 1% between 2025 and 2069 and 6.5% between 2070 and 2100, while under RCP 8.5, temperatures are expected to rise by 3.7% between 2025 and 2069 and 12.7% between 2070 and 2100. The Standard Precipitation Index (SPI) was used to translate these projected climatic anomalies into future drought prevalence. The results suggest that RCP 4.5 forecasts an 8% increase in drought prevalence, while RCP 8.5 projects an 11% increase in drought frequency, with a greater rise in moderate and severe droughts and a decrease in extreme drought occurrences.