main tributary is Arroyo Hondo. The watershed includes three man-made reservoirs: Lake Del Valle, San Antonio Reservoir and Calaveras Reservoir. The Alameda Creek Watershed can be divided into six major reaches: Alameda Creek Flood Control Channel – the channelized, trapezoidal section extending from the Bay upstream to the Niles Canyon area Niles Canyon – the area above the flood control section to the confluence of the Alameda Creek mainstem and Arroyo de la Laguna Upper Alameda Creek (above the confluence with Arroyo de la Laguna) – the reach extending up the mainstem of Alameda Creek into the canyons of the Sunol-Ohlone Regional Wilderness Area and beyond Arroyo de la Laguna – the reach paralleling Interstate 680 upstream of the confluence with the mainstem Alameda Creek, including the Alamo Canal, to its source at the confluence of South San Ramon Creek and Arroyo Mocho Arroyo Valle – the reach extending from the confluence with Arroyo de la Laguna upstream through Shadow Cliffs Regional Park to Del Valle Regional Park Arroyo Mocho – the reach extending upstream from the confluence with Arroyo de la Laguna through the Livermore–Amador Valley and into unincorporated ranch and agricultural lands A more comprehensive list inclusive of minor as well as major named tributaries includes (from top of mainstem heading downstream) Valpe Creek (right), Bear Gulch (right), Whitlock Creek (right), Calaveras Creek (left), Leyden Creek (left), Indian Joe Creek (right), Welch Creek (right), Haynes Gulch (left), Pirate Creek (left), San Antonio Creek (right), Arroyo de la Laguna (right), Stonybrook Canyon (right) and Dry Creek (right). Alameda Creek now runs through the man-made Alameda Creek flood channel near the Bay, the latter is parallel to and south of the old Alameda Creek channel. Ward Creek is tributary to old Alameda Creek. Ecology, past and present Alameda Creek historically supported spawning runs of at least three salmonid species: steelhead (the anadromous form of the coastal rainbow trout Oncorhynchus mykiss irideus), coho salmon (Oncorhynchus kisutch) and chinook salmon (Oncorhynchus tshawytscha). Confirmation that adult steelhead recently captured attempting to migrate into the Alameda Creek watershed, and the rainbow trout sampled in the upper watershed (trapped above complete migration barriers), are native fish that have their closest genetic associations with other populations within the federally threatened steelhead Central California Coast Evolutionarily Significant Unit has spurred a major effort to restore this historically important steelhead stream by removing barriers to migration and improving