If you went to school in San Diego while in the fourth grade, you studied the chain of California Missions, and in particular, Mission San Diego de Alcala. The mission is the birthplace of California and its Spanish roots, and it is the link to the past. But there is a hidden part of the mission that played an important part in the establishment of the mission settlement: the Old Mission Dam.
The mission was founded in 1769 by Father Junipero Serra and its original settlement was actually at the location now known as Presidio Park, just above Old Town. But five years later, the mission was moved to its present location in Mission Valley, in part to have better access to dependable water (the San Diego River was actually a useful river back then).
The friars scouted out a location about six miles upriver as an ideal spot to construct a dam and basin, but construction wasn’t begun until 1809. Indian labor from the mission’s population was used to build the dam and flume and it was one of the most ambitious in the California mission chain.
According to archaeologist Ruth Alter, the dam was built across the head of Mission Gorge, the 244-foot long, 13-foot thick, 13-foot wide dam was constructed of stone and cement on exposed bedrock, creating a permanent reservoir behind it. Water was released through gates and spillways into a six-mile long gravity fed tile lined flume, down the gorge and Mission Valley, ending in a settling basin near the Mission. Construction was completed by 1815 and the padres had the water they needed.
The usefulness of the dam to the mission would not last very long: the missions were secularized in 1833 and by 1867, the dam was in disrepair and mostly in ruins. The remains of the dam are still in place, but the flume system is long gone.
Today, you can still visit the Old Mission Dam as part of the Mission Trails Regional Park. In fact, there is still a pool of water that is held back by the now historic structure.
The Old Mission Dam is a nationally registered historic landmark and a starting point for hikes into Oak Canyon, the East Fortuna Mountain region, or along Father Junipero Serra Trail and the San Diego River. This is an excellent area for bird watching and just relaxing. The pathway to the San Diego River is wheelchair accessible.
Father Junipero Serra Trail and the Old Mission Dam parking lot are open 8:00 a.m. to 5:00 p.m. from November 1 through March 31, and 8:00 a.m. to 7:00 p.m. from April 1 through October 31.
courtesy of: http://sandiego.about.com/