The building of acequias, or irrigation canals, was an important element in Spanish efforts to colonize Texas. Much of the region occupied by the Spanish in Texas was semiarid, and irrigation was vitally necessary for the success of agriculture. Acequias had been widely used throughout Spain since the time of the Moorish conquest, and the early Spanish colonists brought with them sophisticated knowledge of how to construct large-scale irrigation systems. The earliest acequias in Texas were dug near Ysleta, below El Paso, after 1680 by Pueblo Indians under the supervision of Spanish friars. These first acequias eventually became part of a large irrigation network, portions of which were still in use in the early 1990s.
In the mid-1700s acequias were also planned or constructed at Nuestra Señora del Rosario Mission, near the site of present Goliad, at Nuestra Señora de la Candelaria Mission, near the site of present Montel, and at a number of other sites. Later, particularly after Mexican independence from Spain, numerous private acequias were built by the owners of ranchos or small farms.
The most extensive network of acequias, however, was found in San Antonio and the surrounding area. The oldest acequia there was the Concepción, or Pajalache, built in 1729, which followed a route running along what is now Garden and Roosevelt streets to Nuestra Señora de la Purísima Concepción de Acuña Mission, and from there to its lands further south. The Concepción acequia was the largest of the irrigation canals in the region and, according to tradition, was of ample size to allow the Franciscans to employ small boats to transport themselves to and from the mission and to repair the canal. It was in continual use until 1869, when it was abandoned.
Other acequias in the San Antonio area included the Acequia Madre de Valero, dug between 1718 and 1744, which ran from San Pedro Springs through the town to the farmlands below; the Upper Labor acequia in the northern portion of the city, begun in 1776; the San José y San Miguel de Aguayo Mission acequia, built around 1730; the San Juan Capistrano Mission acequia, constructed in 1731; and the San Francisco de la Espada Mission acequia, constructed between 1731 and 1745. The last included the stone Espada aqueduct, which spanned an arroyo; it is claimed to be the only Spanish structure of its type still in working use in the United States.
In addition to the irrigation canals built by the missions, several public acequias and ancillary ditches were built in the San Antonio area to serve the presidio and the lands of the Canary Islanders at the Villa de San Fernando. The construction and maintenance of the acequias required considerable amounts of labor, and some of the larger canals took more than two decades to complete. Because of their high cost, the amount of irrigated land was limited, and competition for such land was strong. Much of the better land went to the Canary Islanders, who constituted the local political and socioeconomic elite. Water rights were strictly controlled and were sometimes sold or bought separately from the land. Landowners were expected to help dig new irrigation ditches and to defray the expense of upkeep. Those who failed to comply with regulations to keep the canals in working order were subject to fines.
After the missions were secularized in the early 1790s, the city authorities undertook to oversee the distribution of water. City control was discontinued in the later half of the nineteenth century, and the remaining acequias were operated for a time as informal community enterprises or, in the case of the San Juan acequia, by an incorporated mutual company. With the expansion of San Antonio in the twentieth century most of the canals were abandoned, though traces of most of them are still evident. See also IRRIGATION.