Let’s take a whirlwind tour, through time and space, and into the heart of one of California's early engineering achievements, the impressive Calaveras Dam.
Imagine the sounds you'd hear in the early 1900s when the original Calaveras Dam was under construction. At 210 feet, it stood as the highest earth-fill dam in the world.
Water flows into Calaveras Reservoir from three sources: Calaveras Creek, Arroyo Hondo, and occasionally from upper Alameda Creek, diverted through a tunnel at the Alameda Creek Diversion Dam. Built in 1931 to divert water to the Reservoir, this dam completely blocked fish from migrating upstream or downstream, until 2019. More on that in a moment.
Prior to 1966, water released from Calaveras Reservoir flowed into Alameda Creek and through Sunol's filter galleries, and Water Temple, before funneling into the Sunol Aqueduct, in Niles Canyon. Now out of use, overgrown, and almost forgotten – this once-vital conduit delivered water to pipelines running under the Bay to San Francisco.
Today, water from Calaveras Reservoir is filtered at the Sunol Valley Water Treatment Plant, prior to entering the Alameda Siphons and the Hetch Hetchy Regional Water System aqueduct. This system delivers an essential supply of water to communities across the Bay Area.
Now imagine the sound you'd hear if you were a steelhead, swimming towards upper Alameda Creek, and coming across a fish ladder next to the diversion dam.
A fish ladder is a unique structure, designed to help migrating fish, swim past barriers. Three fish ladders have been installed in Alameda Creek, including one built by the San Francisco Public Utilities Commission in 2019. It allows steelhead to swim beyond the diversion dam, to their spawning grounds, for nest-building and egg-laying.
Adult steelhead use the fish ladder to navigate as much as a 35-foot climb, alternating between swimming, jumping, and resting in a series of cascades and pools. It can take steelhead a day or more to reach the top, completing part of a remarkable journey, fueled by an innate drive and determination.
For nearly a century, upper Alameda Creek was not accessible to steelhead and other fish. Thanks to projects completed by the San Francisco Public Utilities Commission, the Alameda County Water District, and other partners, these fish can now continue their ancient spawning migration, to upper Alameda Creek.