Drought is generally defined as “a deficiency of precipitation over an extended period of time (usually a season or more), resulting in a water shortage.” As the different definitions at right illustrate, though, drought can be difficult to define—so difficult, in fact, that in the early 1980s researchers found more than 150 published definitions of drought, reflecting differences in regions, needs, and approaches. Some drought definitions are conceptual—an idea or concept—which...
