Aggregate Dryness Index (ADI)
Index name: Aggregate Dryness Index (ADI).
Ease of use: Red.
Origins: The result of work done at California State University, United States by Keyantash and at the University of California-Berkeley, United States by Dracup in 2003.
Characteristics: A multivariate regional drought index that looks at all water resources across many timescales and impacts. It was developed to be used across uniform climate regimes.
Input parameters: Precipitation, evapotranspiration, streamflow, reservoir storage, soil moisture content and snow water content. The inputs are only used if the region for which ADI is being calculated contains the variable.
Applications: Can be used in the context of multiple types of droughtimpacts. Looking at the total amount of water in a climate regime allows a better understanding of water availability to be made.
Strengths: Takes into account water stored as well as moisture that comes from precipitation.
Weaknesses: Does not take into account temperatures or groundwater, which are accounted for in the description of the ADI.
Resources: The methodology and mathematics are explained in the literature, with examples provided. No code is available for this index.
References: Keyantash, J.A. and J.A. Dracup, 2004: An aggregate drought index: assessing drought severity based on fluctuations in the hydrologic cycle and surface water storage. Water Resources Research, 40: W09304. DOI: 10.1029/2003WR002610.