| Cottonwood Creek | |
| Name Other: | Arroyo Alamo |
| Name Etymology: | Spanish |
| Pushpin Map: | USA California |
| Pushpin Map Size: | 250 |
| Pushpin Map Caption: | Location of the mouth of Cottonwood Creek at San Luis Reservoir in California |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | California |
| Subdivision Type3: | Region |
| Subdivision Name3: | Merced County |
| Source1: | source |
| Source1 Coordinates: | 37.1247°N -121.19°W |
| Source1 Elevation: | 2080feet |
| Mouth: | mouth |
| Mouth Location: | Confluence with San Luis Reservoir, Merced County |
| Mouth Coordinates: | 37.105°N -121.1325°W |
| Mouth Elevation: | 548feet |
Cottonwood Creek is a southeastward-flowing 4miles tributary stream of San Luis Creek,[1] originating in the eastern foothills of the Diablo Range in Merced County, California. The creek's mouth, before the San Luis Dam was built across the course of San Luis Creek, was originally at its confluence with San Luis Creek at approximately 250feet. Today, Cottonwood Creek enters San Luis Reservoir, which raises the elevation of the creek's mouth to 548feet, where it becomes Cottonwood Bay on the north side of the reservoir. The source of the creek is at Red Hill, a summit on the eastern slope of the Diablo Range.
Cottonwood Creek, originally named by the Spanish Arroyo Alamos, was named for the Fremont cottonwood (Populus fremontii) trees which are still abundant along the lower creek.[2]
The Upper and Lower Cottonwood Creek Wildlife Areas are administered by the California Department of Fish and Wildlife (CDFW), and bracket the historic mouth of Cottonwood Creek, now submerged as Cottonwood Bay on San Luis Reservoir. This area is now home to a herd of tule elk, visible from the Pacheco Pass (Highway 152), which dispersed there from 1978 to 1981 CDFW translocations of the large ungulates to the Hewlett-Packard San Felipe Ranch on Mt. Hamilton in Santa Clara County.[3]