Mapping drought patterns and impacts: A global perspective – A research report by IWMI

Regions with an unreliable and vulnerable nature of river discharge, and having the largest drought deficits and durations are highlighted in this report.

This study by the International Water Management Institute (IWMI) examines the global patterns and impacts of droughts through the mapping of several drought-related characteristics – either at a country level or at regular grid scales. Characteristics cover various aspects of droughts – from global distribution of meteorological and hydrological drought risks to social vulnerability and indices related to water infrastructure.

The report begins with a review which suggests that while the research and mapping of disaster risks, water scarcity, climate change and related subjects has been significant, there has been little, if any, attempt to date to comprehensively describe and map various aspects and impacts of a drought as an individual natural disaster and as a global multifaceted phenomenon. The aim of this study is, therefore, to start filling this niche.

The study should be seen as a starting point for global mapping of drought patterns. A limited set of maps which is designed and analyzed in this study may, with subsequent contributions from other research groups, develop into a comprehensive global drought indicators’ ‘atlas’ in the future.

The maps are produced by integrating a number of publicly available global datasets. The subsequent discussion of maps allows a number of policy relevant messages to be extracted. It appears that arid and semi-arid areas also tend to have a higher probability of drought occurrence.

The report has a section on “Drought Characteristics and Indices” which briefly describes the indices and characteristics presented and mapped in this study – primarily focusing on the origin of indices and rationale for mapping.

Some of them are drought related indices, which were either used locally rather than globally, or used out of the context with drought studies. Some others are existing indices, which although designed for a different purpose originally, carry useful drought-related information if used either as is or with certain modifications.

Mean Drought Run Duration
Fig: Mean Drought Run Duration based on monthly river discharge (sum of durations of all identified drought runs divided by the number of runs)

The report points out that in drought years, the highest per capita loss of river flow occurs in areas that do not normally experience climate–driven water scarcity.

It also illustrates that the African continent is lagging behind the rest of the world on many indicators related to drought preparedness and that agricultural economies, overall, are much more vulnerable to adverse societal impacts of meteorological droughts.

Regions with an unreliable and vulnerable nature of river discharge, and having the largest drought deficits and durations are highlighted, pointing to the danger of focusing on drought mitigation measures on river flows alone.

The ability of various countries to satisfy their water needs during drought conditions is examined using storage-related indices.

Download the report here -

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