“A hydraulic empire is a social or government structure which maintains power and control through exclusive control over access to water. It arises through the need for flood control and irrigation, which requires central coordination and a specialized bureaucracy. The term can be generalized to cover any power structure maintained by exclusive control of a basic resource needed to live. Though tribal societies had structures that were usually personal in nature, exercised by a patriarch over a tribal group related by various degrees of kinship, hydraulic hierarchies gave rise to the established permanent institution of impersonal government. Most of the first civilizations in history, such as Ancient Egypt, Mesopotamia, China and pre-Columbian Mexico and Peru, are believed to have been hydraulic empires. The typical hydraulic empire government is extremely centralized, with no trace of an independent aristocracy—in contrast to the decentralized feudalism of medieval Europe.