An ensemble empirical mode decomposition of consecutive dry days in the Zambezi Riparian Region: Implications for water management

The Zambezi Riparian Region (ZRR) is a lifeline and home to ~40 million people who depend heavily on the river basin for their livelihood. It also furnishes 8 of its riparian countries with goods and services on which hydropower production and food security anchor. The sustainability of the ZRR is threatened by extreme climate events. Here, we interrogate consecutive dry days (CDDs), an effective metric of extreme climatic events with implications on drought-driven water availability. We use ensemble empirical mode decomposition (EEMD) to understand CDDs. Results indicate that periodic characteristics of CDDs are generally few and mainly at the intra and interannual timescales. Further, the interannual variability of CDDs was found to exhibit a meridional pattern with increments propagating south-eastwards thus, areas in the south-eastern part of the ZRR (e.g. Northern Zimbabwe, Northern Mozambique, and the southern parts of Zambia) have a CDD stress disadvantage. These results suggest that the challenge of putting in place anticipatory actions should primarily focus on these fragile areas of the ZRR. Additionally, findings embodied herein provide climatic antecedent conditions for extreme events and the relevant information for long-term climate forecasts in the region. As such, these findings contribute to deepening our understanding of future risks associated with climate extremes thus, facilitating policy-making processes.

Automated summary

The Zambezi Riparian Region is a vital ecosystem, supporting about 40 million people who heavily rely on its water resources. However, the region is facing threats from extreme climate events, particularly an increased number of consecutive dry days, which impacts water availability. The study found that consecutive dry days exhibit periodic characteristics, mainly at the intra and interannual timescales. The southern vulnerable areas experience higher stress from consecutive dry days and require enhanced anticipatory actions.