High Quality Content by WIKIPEDIA articles! Aliso Creek (Spanish for "Alder Creek"; also called Alisos Creek) is a 19-mile (31 km)-long urban stream that runs through Orange County in the U.S. state of California from the Santa Ana Mountains to the Pacific Ocean, collecting seven main tributaries. The creek is mostly channelized, and as of 2004, the 30.4-square-mile (78.7 km2) watershed had a population of 149,087 divided among seven incorporated cities.