Located to the north of Mission Espada are the remnants of what was once a much more extensive system of water control and irrigation planned and constructed by the monks who manned the missions along the banks of the San Antonio River. The Espada Dam enabled the missions to collect water from the river and divert it via a limestone aquaduct over the Piedras Creek into the acequias, or irrigation ditches, of the fields nearby. While the main current of the river has been diverted to protect the system, it still carries water into the fields as it did in the eighteenth century.