ABSTRACT
Water is the most ubiquitous yet most variable of the mineral resources of the world. Alone among the constituents of our environment, water may be found simultaneously in one area as a liquid, a gas, and a solid. Unlike most other Earth resources, water (on land and in the atmosphere) is also continuously variable in its availability in one state or another. A further complication is that, geographically speaking, its patterns of concentration are always changing.
