Drought is a prolonged dry period in the natural climate cycle that can occur anywhere in the world. It is a slow-onset disaster characterized by the lack of precipitation, resulting in a water shortage. Drought can have a serious impact on health, agriculture, economies, energy, and the environment. People describe it as a “creeping phenomenon” because it slowly impacts many sectors of the economy and can last from just a few weeks or months to multiple years.

Just as drought is difficult to define, it’s also difficult to monitor—particularly to mark the beginning and end of a period of drought.

The Importance of Drought Monitoring

• Drought monitoring involves measuring changes in precipitation, temperature, and surface and groundwater supplies, among other factors.
• Drought indicators for a community should be selected based on its specific drought impacts.
• A drought early warning system can initiate actions that mitigate the impacts of drought on a community.

Drought Monitoring Indicators and Indices

• Drought monitoring involves observing indicators and indices that evaluate changes in a region’s hydrological cycle.
• Drought indicators describe drought conditions and include precipitation, temperature, streamflow, ground and reservoir water levels, soil moisture, and snowpack.
• Drought indices, which include indicators, provide measurements to describe the severity, location, timing, and duration of drought and the impact of drought on a region over time.
• Indicators and indices can be used on their own, in combination, or in a large composite indicator.

Drought Monitoring Indices

• Enhanced Vegetation Index (EVI)
• Evaporative Stress Index (ESI)
• Normalized Difference Vegetation Index (NDVI)
• Temperature Condition Index (TCI)
• Vegetation Condition Index (VCI)
• Vegetation Drought Response Index (VegDRI)
• Vegetation Health Index (VHI)
• Water Requirement Satisfaction Index (WRSI and Geospatial WRSI)
• Normalized Difference Water Index (NDWI) and Land Surface Water Index (LSWI)
• Soil Adjusted Vegetation Index (SAVI)

Conclusion

EOfactory offers a unique toolset for studying droughts and their impacts on ecosystems. The unprecedented scale of available global observations has shed light on the biophysics of the drought phenomenon and has led to new drought indicators for research and practical applications.