The socioeconomic and environmental impacts of droughts have increased significantly, particularly among the most vulnerable groups in Asia and the Pacific. Drought impacts are functions of both the enormity of the water shortage and susceptibility on ground conditions. Three main physical drought types have been established: meteorological, agricultural, and hydrological droughts. Drought indices are derived by assimilating drought indicators into a single numerical value. Traditionally, reservoir storage, stream flows, soil moisture, and ground water table have been used for assessment and monitoring of drought. Spaceborne observations have been used to monitor drought-related variables from a meteorological viewpoint and also to assess and quantify drought impacts from an ecosystem perspective. The standardized precipitation index assigns a single numerical value to the precipitation that can be compared across the regions with markedly different climatic conditions. The percent of normal precipitation is one of the simplest measurements of rainfall for a location.