SPI-based drought characteristics using CHIRPS over Zambia: 1981–2024

Droughts are becoming more frequent, intense and severe. However, there is lack of information on the drought characteristics in developing countries like Zambia. Further, the spatio-temporal changes in drought characteristics have received little consideration in relation to meteorological and agricultural droughts. Therefore, the aim of this study was to assess Standardized Precipitation Index (SPI)-based drought characteristics (events, duration, inter-arrival time, magnitude and severity) across Agro-ecological Regions in Zambia. The climate_indices python package was applied in computing SPI based on Gamma distribution at 1-, 3- and 6-month/s timescales using CHIRPS v2 data from 1981–2024 for ONDJFM. Drought thresholds of SPI < −1.2 were computed using the theory of runs. Results show that inter-arrival time at SPI-1, SPI-3 and SPI-6 exhibited significant increasing trends (p-value <0.05). However, drought events, magnitude and duration at SPI-6 exhibits significant decreasing trends. The combined drought categories increases from SPI-6 (19,392) followed by SPI-3 (19,619) and SPI-1 (20,260). The detected drought conditions from 1981–2024 was moderately dry. It is therefore, short-term water deficits of up to 6 months are increasing in Zambia and thus they have to be considered in agricultural management, drought assessment and in informing policy, National Development Plan and National Adaptation Plans.