SWALIM - Combined Drought Index

CDI :

Note on use of NDVI

The CDI monitoring tool explores the use of three climatic conditions that influence drought conditions. This includes rainfall, temperature and the Normalised Vegetation Drought Index (NVDI) which is a proxy of soil moisture. The NDVI is a dimensionless index that describes the difference between visible and near-infrared reflectance of vegetation cover and can be used to estimate the density of greenness on an area of land.

Since the beginning of 2021, there has been a poor correlation of the NDVI and the ground information, therefore resulting to false values of CDI. In this regard, the use of NDVI in generating CDI values has been halted. Meanwhile, SWALIM is in the process of looking for alternative component to represent soil moisture in place of NDVI

The current values of CDI shown on the map does not include the NDVI values rather a combination of temperature and rainfall.

List of Acronyms

CDI: Combined Drought Index

PDI: Precipitation Drought Index

TDI : Temperature Drought Index

NDVI : Normalized Difference Vegetation Index

RFE : Rainfall Estimates

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LEGEND

Value	Tag	Description
< 0.4	extreme	Major loss of crops and pasture, extreme fire danger, total water shortages, drying of deep reservoirs and usage restrictions
0.4 - 0.6	severe	Wider scale of loss of crops and pastures, imposed water rationing and livestock migration
0.6 - 0.8	moderate	Damage to crops, pastures, drying of shallow reservoirs; voluntary water rationing
0.8 - 1.0	mild	Going into drought, short term dryness slowing planting, growth of crops. Also coming out of a drought – water deficits, partial loss of crops and pasture
> 1.0	normal	No drought