Old mission dam and flume: preliminary findings of new research on the waterworks system of mission San Diego de Alcalá, San Diego County, California.
The Old Mission Dam and Flume is an historically significant system of water control structures on the San Diego River, San Diego County, California. This system, designed and built from the late 1700s to the early 1800s by Franciscan missionaries and Kumeyaay Indians associated with the Mission, was intended to provide a reliable year-round supply of water to Mission San Diego de Alcalá and to the irrigated fields supplying crops to the Mission and the Presidio. The dam itself remains largely intact, but the outlet works, other appurtenances, and most of the flume that directed water to the Mission fields have either been destroyed or are inaccessible. The few published descriptions of the dam and flume system provide conflicting and occasionally fanciful accounts of this important structure. The objectives of this paper are to resolve some of these discrepancies based on a critical evaluation of the published literature and field measurements of the remaining structures, and to identify issues requiring additional work. This paper also serves as a preliminary report of ongoing research into the Mission water system, to be published at a later date.