The San Juan Creek watershed covers in south Orange County and a very small portion of Riverside County. The Santa Ana Mountains occupy most of the north, east and south parts watershed, while the San Joaquin Hills border the watershed on the southwest. Along with San Juan Creek, the two largest tributaries - Trabuco and Bell Creeks - both originate in the Santa Ana Mountains. Although more than half of the watershed is undeveloped land, it also includes parts of the cities of Dana Point, Laguna Hills, Laguna Niguel, Mission Viejo, Rancho Santa Margarita, San Clemente, San Juan Capistrano, and the unincorporated communities of Trabuco Canyon (near Rancho Santa Margarita) and Rancho Mission Viejo (east of San Juan).