The San Gabriel Watershed, located in southern California, covers an area of approximately 649 square miles. The hydrology of the watershed is characterized by steep, rugged terrain that leads to high water runoff rates during precipitation events. The area is also subject to periodic drought conditions. Snowpack in the watershed is limited, with the highest elevations typically receiving less than five feet of snow per year.
Surface water in the San Gabriel Watershed is predominantly managed by the Los Angeles County Department of Public Works. Major reservoirs in the area include the San Gabriel Reservoir, Morris Reservoir, and Cogswell Reservoir. These reservoirs serve as important sources of drinking water for the surrounding communities.
The San Gabriel Watershed experiences a Mediterranean climate, characterized by hot, dry summers and mild, moist winters. Over the past several decades, the area has experienced significant increases in temperature and decreases in precipitation, leading to concerns about water availability and wildfire risk.