The initial success of any new mission was dependent upon the planting and harvesting of crops. Sparse rainfall and the need for irrigation water made the design and installation of an acequia system a high priority. So important was irrigation in Spanish Texas that cropland was measured in suertes, the amount of land that could be watered in one day.
The Moslems introduced the use of acequias (irrigation ditches) to the arid regions of Spain. Once arrived on the frontier, the Franciscans found the system well suited for use in the desert Southwest. In order to distribute the water, missionaries and Indians built seven gravity-flow ditches, five dams and an aqueduct-a 15 mile network that irrigated about 3,500 acres of land.
The best preserved of these acequias is the one near Mission Espada. Espada Dam, completed by 1740, diverted river water into an acequia madre (mother ditch). It is still in operation, but now plays a secondary role beside the modern dam. The water was carried over Piedras Creek through Espada Aqueduct-one of the oldest arched Spanish aqueducts in the United States. Using floodgates, the aguador (water master) controlled the volume of water sent to each field for irrigation and for such auxiliary uses as bathing, washing, and power for mill wheels. Today, nearby farms still use the water from this system.