ABSTRACT
In all areas of the Bajio one finds innumerable references to masonry irrigation gates. At the other end of the Bajio, many haciendas of San Juan de Rio also relied on storage dams. Masonry storage dams were the principal instruments of irrigation on minor arroyos and the small rivers of the northwest Bajio. Masonry fixtures were placed at intervals within the ditches to regulate the distribution of water. The technology of irrigation is so intimately related to the techniques of determining a level line that the medieval irrigation specialists of eastern Spain were called livelladores or levelers. The Hacienda Castillo had long irrigated from headgates located near the confluence of the River Queretaro and the River Pueblito. The irrigation system of the Hacienda Espejo, built in the mid-eighteenth century, represents a triumph of colonial engineering skill. The Hacienda Espejo itself embraces a small oval valley that lies just above the valley of Queretaro.
