Drought: The knowledge base

Drought is an irregular and recurrent natural feature of climate. For the purposes of this discussion, drought represents an accumulated deficit in the water budget of some system of interest, leading to one or more impacts on that system. Such impacts are usually viewed and labeled as negative, but can be positive from other perspectives; indeed, some natural systems have evolved to obtain advantage from sporadic dry conditions. Such systems may be hydrological, agricultural, biological, ecological, or economic. Impacts from a given sequence of atmospheric events can vary, sometimes substantially, among different sectors, depending on sequencing and timing, prior climate history, and the existing condition of the system of interest.