Morena Dam is a concrete arch dam located in San Diego County, California. It was built in 1912 by the Morena Rock Company to provide irrigation water for crops in the surrounding areas. The dam has a height of 155 feet and a length of 540 feet. It impounds the waters of the Cottonwood Creek and is used as a storage reservoir for the City of San Diego.

The hydrology of the dam is sourced from both surface flow and snowpack. The dam collects water from the Cottonwood Creek and from the mountainous regions surrounding the area. The snowmelt from the nearby Laguna Mountains also contributes to the water supply of the dam. The water stored in the dam is used for agricultural purposes and for recreation, including fishing and boating.

The dam has faced a few challenges in the past, including the 2003 Cedar Fire, which burnt a significant portion of the watershed that supplies water to the dam. Despite this, the dam has continued to provide a reliable water supply to the surrounding communities.