Drought Definition: A Hydrological Perspective

Abstract

This paper summarises different techniques for defining a drought. Hydrologists as distinct from economists or social scientists define drought according to water deficits in some component of the hydrological cycle (precipitation, soil moisture, river flow and groundwater) or the impact on the level of service provided to public water supply, irrigation or hydropower demands. Generic features of droughts are their severity, frequency, duration and spatial extent. For operational purposes it is essential that a wide range of analytical procedures are used according to the response characteristics of the resource system. However, for comparisons of drought severity over time and between countries, there may be merit in applying simple procedures for drought frequency assessment.