By Sarah Bardeen
This piece originally appeared on the PPIC Blog, here.
California has just experienced its third reasonably wet winter in as many years. How unusual is this? And how might three such winters in a row affect salmon? We interviewed Jeffrey Mount, senior fellow with the PPIC Water Policy Center, and Carson Jeffres, senior researcher and lab director at UC Davis’s Center for Watershed Sciences, to find out.
We’ve just had three years of decent rain in Northern California, and winter isn’t over yet. Is this unusual?
Jeffrey Mount: Typically, a wet year is followed by a dry year. I would call this a wettish year—almost entirely north of Sacramento. It’s unusual to have three in a row. We have not seen this since the late ‘90s. One quirk of these recent storms is that the state is sharply divided—it’s still very dry in the south.
Carson Jeffres: California has been quite dry and often in drought since around 2012, with two intervening wet years in 2017 and 2019. Overall, it has been pretty grim for salmon, and freshwater ecosystems have paid the price: the salmon fishery has been closed for the past three years.
What might three consecutive wet years mean for salmon in California?
CJ: These recent wet years constitute a huge opportunity for salmon, even though their numbers are way down.
Most salmon in California have a three-year life cycle: they hatch, migrate to the ocean, spend two years there, and then return and reproduce in the river where they were born. A wet year creates conditions that allow juvenile salmon to get washed onto floodplains and into estuaries, where they grow very fast, giving them a leg up before they head out to sea. The evidence for this is solid: when juvenile salmon can fatten up on floodplains and tidal wetlands, they’re more likely to survive. The abundant water also helps them avoid predators and travel to the ocean.
Let me give you an example. In 2018, just 2,500 spring-run salmon returned to Butte Creek. Then the Camp Fire happened, and that whole 2018 cohort of salmon eggs was exposed to sediment and toxic debris runoff from the burned areas. We expected that runoff to harm the newly hatched fish, but the wet winter created favorable conditions for the young fish to grow on floodplains. Two years later, nearly 23,000 of those juveniles returned as adults to spawn. That’s ten times more than their parents’ generation!
We hope to see that experience replicated in the coming years, but we have to remember that ocean conditions—the thing we have the least control over—play an important role.
JM: This winter, a series of atmospheric rivers in late 2024 produced a lot of runoff and high flows on the rivers. Then, four atmospheric rivers in early February meant Shasta and Oroville dams had to dump a lot of water— producing a second pulse of water in the Sacramento system. These pulses were timed perfectly for winter-run salmon.
CJ: High-flow events are like shaking a snow globe—juvenile fish scatter into wetlands and side channels where there’s food, slower water, and low predation. All the things that make salmon happy were taking place.
In February, adult winter-run salmon begin their migration up to the Sacramento River to spawn, and that big pulse of water will help them reach their breeding grounds. We’ve gotten lucky—in one winter, the stage has been set for the successful out-migration of juveniles followed by the successful return of adults.
What can we do for salmon in wet years to help them get through the dry?
CJ: This is where the rubber meets road. There are two really important things we need to do during wet years. First, we can provide more opportunities for water and fish to spread across floodplains during these high flows. And second, we need to store some of that water for dry times and release it when the fish need it most.
JM: That’s why we recommend developing an ecosystem water budget and someone to manage it. We need someone like Carson to monitor conditions and run a little more water through the rivers in dry periods to help fish get out to the ocean or into floodplains. Right now, we can’t do that.
CJ: If the 2020–22 drought had continued, multiple species would be in deep trouble. We got lucky with these three wet years on the Sacramento River, but the general trend is steeply downhill.
We haven’t had structural change in salmon management in the last 20 years, even though our understanding of their needs has advanced considerably. We need to use that information and experiment to learn what works. If we take risks and do things at a big scale, we may be able to recover this important species. Ecosystems and rivers are messy—there’s no way to get it perfect. But continuing to use failing approaches is worse.
I’ve struggled to find hope in recent years as salmon stocks have declined and fisheries were closed, but having three consecutive years of good conditions gives me hope.
Carson Jeffres is a senior researcher, as well as field and lab director, at UC Davis’s Center for Watershed Sciences. Sarah Bardeen is the senior center communications manager at the PPIC Water Policy Center. Jeffrey Mount is a senior fellow at the PPIC Water Policy Center.
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