The San Dimas Experimental Forest (SDEF) is managed by the USDA Forest Service, Pacific Southwest Research Station, as a field laboratory for ecosystem and watershed studies in chaparral and related Mediterranean-climate ecosystems. From its establishment in 1933, the SDEF has been a center for hydrologic research in mountain watersheds.  This research has included intensive monitoring of precipitation and water yield in mountainous terrain and studies that manipulated the natural vegetation across watersheds to maximize water yield.