Drought is a complex phenomenon which is difficult to define, measure and quantify. Drought hazard refers to long physical events during which there is less water than normal. Just as there is no ‘one-size-fits-all’ definition of drought, there is no single index or indicator that can account for and be applied to all types of droughts, climate regimes, and sectors affected by droughts. This webinar will examine indicators and models used for characterizing and monitoring hydrological droughts, which are generally defined as occurring when there is less water than normal in rivers or groundwater. Drought in these compartments of the water cycle is directly responsible for restrictions of water supply for households, industry and irrigated agriculture, and it endangers fish and other biota living in rivers.