In a remarkable testament to ecological resilience and human-led restoration, Putah Creek in California, once severely degraded by decades of water mismanagement, is witnessing an improbable resurgence of chinook salmon, returning in numbers far exceeding expectations. This success story, unfolding along the 85-mile stretch of a creek that flows from the Mayacamas Mountains to the Sacramento River floodplain, offers a vital glimmer of hope for the broader challenges facing aquatic ecosystems in the heavily engineered Central Valley. While the recent, highly publicized removal of four dams from the Klamath River has garnered significant attention, the quiet triumph on Putah Creek underscores the profound impact of restoring even a fraction of a river’s natural hydrological pulse.

The transformation of Putah Creek is a narrative of human intervention and eventual, crucial correction. For years, the creek’s natural flow was systematically manipulated and reduced, its course channelized and its waters warmed, rendering it inhospitable to native fish populations, particularly salmon. This human-centric approach to water management, common throughout California’s Central Valley—a region characterized by its vast agricultural output and intricate water infrastructure—led to the decimation of native species, which were ultimately replaced by invasive, heat-tolerant fish like bass. The situation reached a crisis point in 1989 and 1990 when sections of the lower creek completely dried up, leaving behind a stark tableau of dead fish and highlighting the dire consequences of ecological neglect. The then-city manager of Davis, a city through which Putah Creek flows, lamented the severe stress and mortality experienced by the creek’s wildlife.

However, this period of ecological decline sowed the seeds for future recovery. In 1990, the Putah Creek Council, an environmental advocacy group, initiated legal action against the Solano County agencies responsible for managing the Monticello and Putah Diversion dams, which had been constructed by the Bureau of Reclamation in 1957 to supply water for agriculture and urban use. The lawsuit argued that state law mandated dam operators to maintain healthy fish populations. This legal challenge culminated in a landmark settlement in 2000, known as the Putah Creek Accord. This agreement obligated water managers to release flows in a manner that more closely mimicked the creek’s natural patterns, ensuring it would no longer dry up during summer months and introducing beneficial spring pulses to support fish breeding. Crucially, the accord also introduced a fall surge of water, termed an "attraction flow," designed to entice salmon back to the creek, a strategy met with considerable scientific uncertainty.

Phil Stevens, executive director of the Putah Creek Council, reflected on the accord’s speculative nature, admitting that "Nobody knew whether the salmon would come or not." Despite these uncertainties, the accord represented a significant shift, acknowledging the legal and ecological imperative to restore riverine health. The restored flows, though modest—with 95% of Putah Creek’s water still diverted for human consumption—proved remarkably effective. Complemented by other restoration efforts, such as riparian habitat planting and community-led clean-up initiatives, these altered flow regimes began to revitalize the creek’s ecosystem. By 2012, scientists noted a significant recovery of native fish species, including Sacramento suckers and tule perch, which had "regained dominance."

The true harbinger of this ecological revival arrived in 2013 when eight chinook salmon, drawn by the attraction flows, returned to Putah Creek to spawn, marking the first such occurrence in decades. This initial trickle grew into a significant influx in subsequent years, with several hundred salmon appearing the following year and approximately 1,500 in 2016. The return of these iconic migratory fish prompted the inauguration of a "Salmon Fest" in the town of Winters, an event once considered unimaginable. Christine Parisek, a postdoctoral scholar at the University of California, Davis’s Center for Watershed Sciences, highlighted this astonishing comeback as proof that "it’s possible to recover the ecology of a system" by reintroducing natural flows, even if it requires patience and sustained effort. The fundamental lesson learned was elegantly simple: fish, it turned out, just needed water.

As the salmon population in Putah Creek began to rebound, a critical question emerged: where were these pioneering fish originating from? Salmon are renowned for their instinctual drive to return to their natal streams to spawn. Given Putah Creek’s long absence of chinook, the initial arrivals were clearly "strays" from other river systems. Research conducted in 2020 by Andrew Rypel, a fish ecologist formerly with UC Davis, and his colleagues provided the answer. They discovered that the majority of Putah Creek’s new salmon population consisted of fish that originated from Central Valley fish hatcheries. These fish were often trucked to the San Francisco Estuary during dry years, a process that can lead to poor imprinting on their specific birth waters. Consequently, as adults, these hatchery-raised salmon entered the Sacramento River and, by chance, navigated into the Toe Drain, a warm, channelized ditch that ultimately led them to Putah Creek. While the tendency of hatchery salmon to stray from their intended natal rivers is generally viewed as undesirable, potentially diluting the gene pools of wild fish, the situation on Putah Creek was unique: there were no wild fish to compromise. Rypel observed that "If you do the hard habitat work, the hatchery fish can help you," suggesting that even fish with a compromised origin could contribute to the establishment of a novel population when provided with suitable habitat.

Further scientific investigation shed more light on this remarkable phenomenon. In a 2025 study, Rypel and his team analyzed otoliths—the small, ear bones of fish that record elemental signatures of the waters they inhabit throughout their lives. This analysis revealed that some of the chinook returning to Putah Creek were not solely from hatcheries; a segment had been born directly within the creek, migrated to the ocean, and successfully returned as adults. This indicated that Putah Creek’s accidentally established chinook population was beginning to "rewild," shedding their domestic origins and fully embracing the natural salmon life cycle.

The broader context for this success is the widespread decline of salmon populations across the Central Valley. Dams, water diversions, drought, and other anthropogenic pressures have pushed many of these iconic fish towards the brink of extirpation, with projections suggesting minimal abundance by the end of the century. Putah Creek stands out as one of the few streams in the region experiencing a growing rather than shrinking salmon run. Max Stevenson, Putah Creek’s streamkeeper—a position established by the accord and funded by the Solano County Water Agency—emphasized the inclusive approach to recovery, stating, "You can go ahead and pooh-pooh the hatchery fish, but it’s all hands on deck."

Despite the significant progress, Putah Creek still faces considerable challenges. The creek bed in many areas is compacted or choked with silt, hindering salmon’s ability to find suitable spawning grounds. Stevenson has been actively working to improve spawning habitat by breaking up compacted gravel with heavy machinery and introducing new gravel, though this remains an ongoing effort. A more persistent obstacle is a 10-foot-high check dam that impedes upstream salmon migration until late fall, when irrigation season concludes and water managers remove wooden boards to allow passage. This antiquated system of fish passage proved disastrous in 2021 when torrential rains washed a large volume of organic matter into the creek, leading to low-oxygen conditions that killed incoming salmon before the check dam could be opened, effectively wiping out nearly an entire year’s spawning run. Stevenson is actively pursuing solutions, including the construction of a bypass channel or an underwater fish ladder to allow salmon to navigate the dam, or even upgrading the irrigation infrastructure to enable the dam’s complete removal.

Rypel characterizes the effort to restore salmon in such a profoundly altered environment as "reconciliation ecology"—the practice of creating space for nature within landscapes irrevocably shaped by human activity. The chinook salmon of the Central Valley are increasingly adapted to artificial conditions, including being reared on flooded rice farms, migrating along irrigation canals, and spawning in artificially placed gravel. These engineered environments may represent the future for salmon in Anthropocene California, a landscape profoundly re-engineered by human endeavor, yet still capable of supporting these magnificent creatures if humans choose to create pathways for their return. As Stevenson aptly put it, "We can make a salmon run here if we want one."