San Deigo Historic Site 52 MISSION DAM AND FLUME

The old mission dam, much of which is still standing at the upper end of the Mission Gorge, was part of the first irrigation and engineering projectin California. It was constructed during the first decade of the Nineteenth Century by the priests and Indians of the San Diego Mission. Native rock and cement manufactured from available materials were employed. A gatewas let into the middle of the dam to control the flow of water down the riverbed. By this means it was intended to keep the seasonal San Diego River flowingby the Mission the year around, in order that there would be no dry spell.So much water was lost into river sands and the soil in the miles between thedam and the Mission that the Franciscans commenced work on a flume soon after the dam was completed. It was an aqueduct of tile two feet wide and over one foot deep, which rested on a bed constructed of cobblestones and cement. Its course was along the north side of the gorge. In the Roman fashion, the fall of the flume was uniform and not so great as that of the stream, therefore a good head of pressure was available at the Mission.

This is also a National Historic Landmark.