The 2023/24 summer drought tracked by the Agricultural Drought Early Warning System (ADEWS) for South Africa

Abstract

Commercial grain production in South Africa is largely rainfed and concentrated in semi-arid areas in the summer rainfall region, where drought is a leading cause of low agricultural harvests, sometimes resulting in food insecurity. During the 2023/24 summer growing season, a high-intensity, rapid-onset flash drought occurred from mid-January to late March, resulting in significant grain price increases due to lower production of white maize, the main staple in South Africa. Despite only lasting two-and-a-half months, agricultural impacts were significant because the drought coincided with the peak of the maize growing season during tasselling and grain filling. Using this drought as a case study, we evaluated the ability of a South African Agricultural Drought Early Warning System (ADEWS), available at https://www.drought.agric.za/, in communicating drought conditions and impacts on productivity. This ADEWS integrates weather data, short-to medium-range forecasts, remote sensing data, and crop and rangeland simulation outputs to provide near real-time monitoring of drought indicators. Validation against observed maize yields showed strong performance, with statistically significant correlations between observed maize yields and several ADEWS products, including the Vegetation Condition Index (VCI), maize Water Requirement Satisfaction Index (WRSI), Percentage of Average Seasonal Greenness (PASG), and simulated yields from the Decision Support System for Agrotechnology Transfer – Crop Environment Resource Synthesis (DSSAT-CERES-Maize) model. Despite the limited duration of the drought, ADEWS effectively captured its severity, timing and production impacts. Therefore, this case study reflects the value of ADEWS in keeping stakeholders informed, and in supporting early warning and decision making for drought preparedness in South African rainfed agricultural systems.