Putah Creek, a waterway in California that had long suffered from human intervention, is experiencing a remarkable rebirth, marked by the significant return of chinook salmon. For decades, the river’s natural course and flow were heavily manipulated for agricultural and urban needs, severely damaging its ecosystem. However, a concerted effort to reverse this trend and restore the creek to a semblance of its natural state has yielded unexpected and abundant returns of salmon, serving as a crucial indicator of the aquatic environment’s health. This resurgence on Putah Creek, while less publicized than the recent dam removals on the Klamath River, offers a powerful testament to both human-driven restoration and the inherent resilience of these migratory fish.

The 85-mile journey of Putah Creek, originating in the Mayacamas Mountains where it runs narrow and boulder-strewn, transforms as it approaches the Sacramento River’s floodplain, widening and slowing. Throughout much of its course, however, the creek has been constrained by dams, its waters siphoned for irrigation, and its banks artificially straightened and hardened. Despite being salmon-free for many years, 2025 saw an astonishing influx of over 2,000 chinook salmon returning to spawn, a success that underscores the efficacy of restoration efforts and the tenacity of the species. "It’s the Field of Dreams thing: ‘If you build it, they will come,’" commented Andrew Rypel, a fish ecologist formerly at the University of California, Davis, and now at Auburn University, highlighting the scientific and community collaboration that made this achievement possible.

The history of Putah Creek mirrors the broader narrative of river management in California’s Central Valley, a region characterized by its intensely productive agricultural landscape and ambitious water infrastructure projects, once described by Joan Didion as "plumbing on the grand scale." In 1957, the U.S. Bureau of Reclamation constructed the Monticello and Putah Diversion dams, creating Lake Berryessa to store water for farms and cities. This impoundment drastically altered the creek’s hydrology, leading to warmer, diminished flows that became inhospitable to salmon and many other native fish species, which were subsequently replaced by invasive species like bass that tolerate warmer conditions. The ecological toll became starkly evident in 1989 and 1990 when the lower reaches of Putah Creek dried up completely, leaving thousands of dead fish in the parched riverbed. The then-city manager of Davis, through which the creek flows, lamented that the wildlife was "severely stressed, dying, or dead."

Amidst this ecological decline, the seeds of Putah Creek’s recovery were sown. In 1990, the Putah Creek Council, an environmental advocacy group, initiated a lawsuit against the Solano County agencies managing the dams. Joined later by the city of Davis and UC Davis, their case argued that California law mandated dam managers to maintain fish populations in good condition. This legal action culminated in a landmark 2000 settlement known as the Putah Creek Accord. This agreement required water managers to implement flow regimes that more closely approximated natural conditions, ensuring the creek would no longer dry up during summer months and establishing spring "pulses" to stimulate fish breeding. A crucial element of the accord was the establishment of a fall "attraction flow," a surge of water intended to entice salmon back to the creek, a move that was considered speculative at the time. "It was a speculative, ‘Well, maybe this is going to work’ kind of thing," recalled Phil Stevens, executive director of the Putah Creek Council, admitting that the return of salmon was far from guaranteed.

The flows mandated by the accord, while modest – with 95% of Putah Creek’s water still diverted for human use – proved to be remarkably effective. Augmented by other restoration initiatives, such as riparian planting and community-led cleanups, these altered flows initiated a significant ecological recovery. By 2012, scientists observed that native fish species, including Sacramento suckers and tule perch, had "regained dominance" in the creek. The following year, the first eight chinook salmon in decades, drawn by the attraction flows, ventured into Putah Creek to spawn. This initial success was followed by hundreds of salmon in 2014, and approximately 1,500 in 2016, leading conservation groups to establish a Salmon Fest in the town of Winters, an event that would have been unimaginable just years prior. Christine Parisek, a postdoctoral scholar at UC Davis’s Center for Watershed Sciences, views 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 simple, yet profound, realization was that the fish just needed water.

As the salmon population on Putah Creek began to rebound, a compelling question emerged: where were these fish originating? Salmon are renowned for their homing instinct, returning to their natal streams to reproduce. However, given Putah Creek’s long absence of chinook, the pioneering salmon were evidently "strays" from other river systems. In 2020, research led by Rypel and his colleagues revealed that the vast majority of these new salmon were, in fact, from Central Valley fish hatcheries. During dry years, these fish were transported by truck to the San Francisco Estuary, a departure from their natural life cycle that resulted in poor imprinting on their true home waters. As adults, they entered the Sacramento River and, seeking suitable habitats, navigated up the Toe Drain, a warm, channelized ditch that fortuitously led them to Putah Creek. While hatchery fish are often criticized for diluting the gene pools of wild populations due to their tendency to stray, this phenomenon proved beneficial in Putah Creek, as there were no wild fish present to be negatively impacted. "If you do the hard habitat work, the hatchery fish can help you," Rypel explained, noting how these disoriented strays inadvertently contributed to the formation of a unique salmon population.

Further investigations provided even more intriguing insights. A 2025 study analyzed otoliths – small, calcified structures within a fish’s inner ear that record elemental signatures of the surrounding water as the fish grows. This analysis allowed researchers to determine the natal waters of individual salmon. The otoliths from Putah Creek chinook revealed that some of these fish had not originated from hatcheries. Instead, they had been born in the creek itself, migrated to the ocean, and successfully returned as adults, completing their full life cycle. This indicated that Putah Creek’s inadvertently introduced chinook were beginning to shed their domestic origins and truly rewild.

The broader context for this success is the ongoing crisis facing salmon populations throughout the Central Valley. These iconic fish are contending with a multitude of stressors, including dams, water diversions, and persistent drought, leading to predictions of their potential extirpation or minimal abundance by the end of the century. Putah Creek stands out as one of the few streams where salmon runs are actually growing. "You can go ahead and pooh-pooh the hatchery fish, but it’s all hands on deck," stated Max Stevenson, Putah Creek’s streamkeeper, a role established by the accord and funded by the Solano County Water Agency, emphasizing the collaborative and inclusive approach to restoration.

Despite these significant strides, Putah Creek still faces considerable challenges. Its riverbed is often compacted or covered with silt, limiting the availability of suitable spawning grounds. Stevenson has been actively working to address this by breaking up existing gravel with heavy machinery and importing additional gravel, though the task remains extensive. A more pressing impediment to salmon migration is a 10-foot-high check dam. This structure obstructs upstream movement until late fall, coinciding with the end of the irrigation season. Only then are wooden boards removed, allowing chinook to proceed – a remarkably rudimentary form of fish passage. In 2021, torrential rains delivered a large amount of organic matter into Putah Creek, leading to low-oxygen conditions that tragically killed incoming salmon before the check dam was opened, effectively wiping out nearly an entire year’s spawning run. Stevenson is advocating for solutions such as a bypass channel or an underwater fish ladder to allow salmon to circumvent the check dam, or even upgrading irrigation infrastructure to facilitate its complete removal.

The process of reintroducing salmon to such a profoundly altered environment, Rypel asserts, exemplifies "reconciliation ecology" – the practice of creating space for nature within landscapes irrevocably reshaped by human activity. In the Anthropocene, California’s chinook salmon are adapting to new realities, being raised on flooded rice fields, navigating irrigation ditches, and spawning in artificially introduced gravel. These engineered conditions may well represent the future for salmon in a re-engineered California, a state where human ingenuity has transformed nearly every landscape, yet where opportunities for nature’s persistence still exist, provided we are willing to make space for them. As Stevenson optimistically concluded, "We can build cities, we can make factories, we can go to the moon. We can make a salmon run here if we want one."