10/16/2026
There is a ditch running through the south side of San Antonio that has been moving water to farmland since before the United States existed, and it is still moving it this morning.
The Espada acequia was begun around 1731 and finished by 1745. Spanish engineers laid it out by gravity alone, following a grade so slight that water walks it rather than runs, about twenty three inches of fall per mile today. Where the ditch had to cross a creek, they built an aqueduct in the 1740s: two cut limestone arches with a diamond shaped pier between them, set point first upstream so a flood splits against it instead of shoving it over. The channel on top is four feet wide and four feet deep.
Before that, the water crossed the creek in hollowed out logs.
It is the only Spanish colonial aqueduct in the country still standing and still carrying water. In 1897 a flood ran roughly six feet over the top of it and it stayed put. The mortar has a reputation for having been mixed with egg whites and goat's milk, which is a good story and is not true. What actually happened is less romantic and more impressive. Lime dissolved in the river water precipitated out into the masonry year after year until the structure quietly cemented itself.
Of the seven acequias the missions dug, totaling about fifteen miles, only two still flow, and only one still works the way it was designed to.
The farmers downstream never measured water by the gallon. They measured it in hours. A water hour was your turn, and in 1895 it cost a dollar and by 1968 it cost ten. A ditch commissioner kept the turns honest and had authority to shut a gate on anybody taking more than their share. The Spanish even had a word for the amount of land you could water in a day, a suerte, and over time the word drifted until it simply meant a farm plot.
About a dozen properties still take water off it. Two hundred and eighty years is a long run for a public works project.