A great deal has been said about the "urban revolution"—a process of differentiation that split an originally village-centered agrarian society into an urban and a rural sector: town and village. Prior to the urban revolution and with extraordinary consequences, the fate of agricultural man was profoundly shaped by what may be suitably called the "hydraulic revolution." In hydraulic economy preparatory labor consisted essentially in the gathering, conducting, and distributing of one auxiliary material—water. The chapter suggest that this type of agrarian economy be called "hydraulic agriculture" to distinguish it from rainfall farming and hydroagriculture. Development in political structure is most consequential when the primitive governments of hydraulic tribes, managed largely by part-time functionaries, evolve into statelike organizations, managed by a body of full-time officials. Hydraulic civilization came into being not through a technological but through an organizational revolution.