| Arroyo Viejo | |
| Name Other: | Old Creek[1] |
| Pushpin Map: | USA California |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of Arroyo Viejo in California |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | California |
| Subdivision Type3: | Region |
| Subdivision Name3: | Alameda County |
| Subdivision Type5: | City |
| Subdivision Name5: | Oakland |
| Source1 Coordinates: | 37.7606°N -122.13°W |
| Source1 Elevation: | 450feet[2] |
| Mouth: | San Leandro Bay |
| Mouth Coordinates: | 37.7547°N -122.2014°W |
| Mouth Elevation: | 1feet |
| Tributaries Right: | Arroyo Melrose Highlands Branch, 73rd Avenue Branch |
Arroyo Viejo (“Old Creek” in Spanish[1]) is a westward flowing 5.1miles creek that begins in the Oakland Hills in Alameda County, California, and joins Lion Creek just before entering San Leandro Bay, a part of eastern San Francisco Bay.[2]
The Arroyo Viejo Creek Watershed drains 6.2sqmi beginning on the western slope of the Oakland hills and running west through the northern boundary of Knowland Park then urban Oakland before merging with Lion Creek and entering San Leandro Bay, and finally, San Francisco Bay. Rifle Range Creek begins in the Leona Canyon Regional Open Space park, then joins the Arroyo Melrose Highlands Branch, which is also joined by Country Club Creek (which flows along the northern boundary of Sequoyah Country Club). The Arroyo Melrose Highlands Branch joins Arroyo Viejo at the MacArthur Freeway. Below the freeway, the creek is joined by the 73rd Avenue Branch (which is in an underground pipe), and continues in a series of engineered channels and underground culverts to Lion Creek (also known as Arroyo de Leona)[1] and crosses Interstate 880 to San Leandro Bay within the larger San Francisco Bay.[3]
The upper tributaries of Arroyo Viejo lie in what was historically a belt of coast redwood (Sequoia sempervirens) extending from the Leona Canyon Regional Open Space Preserve up to Redwood Regional Park and east to Moraga.[4]