About the Eswatini Drought Monitor
The Eswatini Drought Monitor provides a monthly assessment of drought conditions across the country using a scientifically robust indicator known as the Composite Drought Indicator (CDI). The system is designed to offer real-time insights to everyone involved in proactive drought preparedness and response in the Kingdom of Eswatini.
What is the Composite Drought Indicator (CDI)?
The CDI combines four different types of drought-relevant datasets into a single map that reflects the overall severity of drought conditions:
- Land Surface Temperature (LST) – measures heat stress and temperature anomalies
- Normalized Difference Vegetation Index (NDVI) – captures vegetation health and greenness
- Standardized Precipitation Index (SPI) – assesses rainfall deficits
- Soil Moisture – reflects water availability for crops and plants
These datasets are combined using a weighted average system, with flexibility to adjust the weights depending on regional characteristics or if certain data is missing.
How is the CDI Computed?
The CDI is generated in a mostly automated process that includes the following steps:
- Data Retrieval – The system checks for the latest datasets from global sources, and automatically downloads and stores LST, NDVI, SPI, and Soil Moisture data.
- Processing – Computes percentile ranks and long-term trends using 40+ years of data where available.
- Weight Adjustment – If needed, experts can change the weight of each dataset depending on data quality or relevance.
- CDI Map Generation – Monthly drought maps (CDI) are produced indicating the drought levels per Inkundla (region).
- Validation – The Technical Working Group (TWG) reviews the maps and provides expert feedback.
- Final Publication – Once validated, the CDI is published and made available to the public on this platform.
What Do the CDI Categories Mean?
CDI drought classifications are relative, meaning they compare current conditions to a long-term historical baseline for each specific location. This helps answer the question: "How rare or severe are current drought conditions compared to what’s typical in this area?"
For example, if an area is classified under Severe Drought (D2), it means that in the long-term record (usually 40+ years), conditions have only been this dry less than 10% of the time. This percentile-based method allows us to detect both long-term droughts and short-lived, extreme events—always in the context of local climate norms.
| Category | Description | CDI Percentile | Meaning |
|---|---|---|---|
| None | Normal or wet | >30.01 | Common or wetter-than-average |
| D0 | Abnormally Dry | 20.01 – 30.00 | Drier than usual, but not yet drought |
| D1 | Moderate Drought | 10.01 – 20.00 | Unusual dryness—seen ~1 in 5 years |
| D2 | Severe Drought | 5.01 – 10.00 | Rarely this dry—<10% of the time |
| D3 | Extreme Drought | 2.01 – 5.00 | Extreme dryness—only ~2–5% of years |
| D4 | Exceptional Drought | 0.00 – 2.00 | Among the driest conditions on record |
Who is Involved in Validation?
The Technical Working Group (TWG)—comprising representatives from Eswatini’s NDMA, the Ministry of Agriculture, MET, Department of Water Affairs (DWA) and the University of Eswatini (UNESWA) —plays a crucial role in the review and validation process.
Their responsibilities include:
- Reviewing the generated maps monthly.
- Benchmarking against other datasets and ground reports.
- Approving or requesting changes before publication.
ABOUT EDM
The Eswatini Drought Monitor is developed through a collaboration between the National Disaster Management Agency of Eswatini, the Ministry of Agriculture, and the Eswatini Meteorological Service.
