This thesis traces the history of irrigation, and related agricultural practices, in a remote valley on the western slope of the Peruvian Andes. Based on three-and-a-half years of ethnographic fieldwork, it presents a comparative study of three communities, one that examines similarities and differences in their use of land, water and labor, in order to show how the local indigenous technology has changed through time. The author argues that hydraulic practices were once quite uniform throughout the highlands, forming a widespread management tradition that was originally imposed by the Incas. By means of careful comparison and generalization, he manages to specify exogenous influences that have drastically altered that tradition, the basis of village life, throughout much of the region during the last two centuries.