Espada Dam and Acequias, Spanish Engineering in Early Texas
Author: Melinda Luna PE
September 2024
Espada Dam and the Espada Acequia are Spanish engineering projects in Early Texas that can still be seen today. The Mission San Francisco De La Espada is part of the National Park System.
The Mission was established in 1690 in east Texas and because of disease, drought, and other factors, it relocated to the San Antonio area. The mission was built to house priests and others to convert the local native Americans to Catholicism thereby establishing Spanish in the New World. The Spanish had learned of the construction of such projects from the Romans and Moors in Europe. Spanish had already begun other projects in the area with San Pedro Ditch, Concepcion, Alamo Madre, and other ditches. The work was done with native American labor and some settlers who received land grants.
The Espada Dam was built over a natural ledge in the San Antonio River. The dam points downstream which is an unusual design. The dam is built of flagstone with cemented gravel and rocks. According to tradition, goat’s milk serves as a cementing agent in the mortar. The height is about 8 feet, and the length is 270 feet. The water behind the dam rose and was diverted to the Espada Acequia. Over time, the sediment in the water would further cement the stones. The dam has experienced many floods as the water rises over the dam. No written records of the building of the project have been found. At the time, grades were laid out by using a frame in the shape of an equilateral triangle, with a plumb line hanging at the apex. The grade of the ditch was reported to be 1.5 per mile. Levees were formed on the banks when each spring the ditches were cleaned out and the sediment deposited on the banks. The acequias were built of the same stone and cement. The aqueduct where it crosses an arroyo are arches with the old Roman rule of making the width or thickness of the piers one-third the arch span. The bottom width of the ditch is 5 feet and once there was 6 miles of ditch length. The system provided water for crops such as corn, pumpkins, beans, melons sweet potatoes, and cotton. The area of irrigation was 3, 500 acres of land or 5.5 square miles.
It is estimated that the dam and acequia stopped being maintained around 1875. In 1895, the Espada Ditch Company was formed to repair the system. The lead in the Ditch company was A. Y Walton, Jr who owned land along the ditch. Water was sold to adjacent landowners to pay for the repairs. In 1941, the San Antonio Conservation Society purchased the property to make sure it was preserved. Then in 1965, the United States Department of the Interior designated Espada Aqueduct as a Registered National Historic Landmark. The Historic American Engineering Record documented the landmark, and the information can be found at the Library of Congress and online https://www.loc.gov/item/tx0217/
The San Antonio River Authority constructed the San Antonio Channel Improvements that were designed to maintain a base flow on the west bank while allowing water to overtop the dam. This project was completed in June 2023.
Many ASCE Texas section members have participated in one way or another in preserving the dam and Acequia itself and its history. Firstly, Edwin P Arneson in the Southwestern Historical Quarterly with his paper Early Irrigation in Texas dated October 1921.
Joesph F Minor at the Texas Tech University, Water Resources Center served as project manager for the HAER project. The ASCE History and Heritage Committee, the ASCE Texas Section, and the ASCE San Antonio branch were sponsors of the project completed in 1968.
The dam and acequias are worth a visit to see the historic National Civil Engineering Landmark in Southern San Antonio, Texas. The system is still providing water to adjacent landowners today.
Historic American Engineering Record, C., Texas Tech University, W. R. C., American Society Of Civil Engineers, C. O. H. A. H., American Society Of Civil Engineers, T. S., American Society Of Civil Engineers, S. A. B., Minor, J. E. & Rogers, G., Lowe, J., photographer. (1968) Espada Acequia, Diversion Dam, San Antonio River, Military Drive vicinity, San Antonio, Bexar County, TX. San Antonio Texas Bexar County, 1968. Documentation Compiled After. [Photograph] Retrieved from the Library of Congress, https://www.loc.gov/item/tx0217/.
