Put simply, droughts are caused by a prolonged depletion of precipitation in a certain ecosystem or climate over a long period of time. Unlike normal dry spells, droughts are so severe that they can thoroughly dry out vast expanses of land, like deserts. Droughts can be extraordinarily damaging and expensive to the people who live in the environments where they occur, especially in terms of the agricultural industry.
According to the National Drought Mitigation Center, a drought is a natural hazard that can result in a serious water deficiency in a given region. Sometimes droughts can take years to develop from the prolonged decrease in rain levels over a long time. Droughts can be caused not only by these naturally occurring problems, but also by the stress and reliance humans have developed on water. When humans require vast amounts of water from their environment for agricultural, cleaning and recreational purposes in addition to drinking, they can drain the ecosystem. This can result in a set of circumstances that facilitates the development of a drought.
Droughts can be devastating, not only to an ecosystem, but also to the economics of the people living where they occur. They can cost billions of dollars in damages and lost productivity.