A NSW Government website

The NSW Combined Drought Indicator (CDI)


Published 3 May 2024

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 ANUClimate data that has been interpolated to a 1 km2 grid 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 PhaseDefinition
Intense Drought All three indicators (rainfall, soil water, plant growth) are below the 5th percentile.
Drought Any indicator is less than the 5th percentile.
Drought Affected (intensifying) Any indicator is less than the 30th percentile AND Negative 5-month Rainfall Index trend (DDI≤0.4).
Drought Affected (weakening) Any indicator is less than the 30th percentile AND Positive 5-month Rainfall Index trend (DDI>0.4).
Recovery All indicators are greater than the 30th percentile AND any indicator is less than the 50th percentile AND the previous category is Drought Affected.
Non-Drought All indicators greater than the 50th percentile or all indicators are greater than the 30th percentile AND the previous category is Non-drought.

Visit NSW DPI's Drought Monitoring page to find out more about the program.