The NSW Combined Drought Indicator (CDI)
The Combine Drought Indicator (CDI) is used by NSW DPI to classify drought in New South Wales. It integrates weather, climate, soil, and land-use datasets into a single framework to help decision making.
The CDI combines meteorological, hydrological and agronomic definitions of drought using indicataors for rainfall (RI), soil water (SWI), and plant growth (PGI). By using multiple indicators, the CDI provides a comprehensive assessment of drought conditions in NSW.
View the Combined Drought Indicator at edis.dpi.nsw.gov.au
The indicators track how rainfall, soil water, and plant growth perform over the last year relative to the historical record. The rainfall indicator is based on Bureau of Meteorology rainfall station data that has been interpolated to a 5 km2 grid (Australian Water Availability Program) and averaged over a period of 12 months. The soil water and plant growth indices are modelled using a soil moisture and crop growth model.
Used together in a logical framework, these indicators are used to categorise drought in NSW:
| CDI Phase | Definition |
|---|---|
| Intense Drought | All three indicators (rainfall, soil water, plant growth) are below the 5th percentile. |
| Drought | At least one indicator is below the 5th percentile. |
| Drought Affected (intensifying) | At least one indicator is below the 30th percentile and the rainfall trend is negative over the past 90 days. |
| Drought Affected (weakening) | At least one indicator is below the 30th percentile and the rainfall trend is positive over the past 90 days. |
| Recovery | All indicators are below the 50th percentile but above the 30th percentile. |
| Non-Drought | At least one indicator is above the 50th percentile. |
Visit NSW DPI's Drought Monitoring page to find out more about the program.