ABSTRACT
Droughts are a normal part of the climate, and they can occur in any climate regime around the world, even deserts and rainforests. Like other hazards, droughts can be characterized in terms of their severity, location, duration, and timing. Droughts can arise from a range of hydrometeorological processes that suppress precipitation and/or limit surface water or groundwater availability, creating conditions that are significantly drier than normal or otherwise limiting moisture availability to a potentially damaging extent. Drought risk management involves hazards, exposure, vulnerability and impact assessment, a drought early warning system (DEWS), and preparedness and mitigation. DEWS typically aim to track, assess, and deliver relevant information concerning climatic, hydrologic, and water supply conditions and trends. This chapter discusses some of the most commonly used drought indicators/indices that are being applied across drought-prone regions, with the goal of advancing monitoring, early warning, and information delivery systems in support of risk-based drought management policies and preparedness plans.
