“Salmon have always been very important to indigenous cultures in our state and all along the West Coast, and just the people that grew up in California. ... A lot of people grow up watching the salmon spawn or going to the hatcheries,” Andrew Rypel, director of the Center for Watershed Sciences and professor at UC Davis, told The Epoch Times.
The creek flows from the Mayacamas Mountains and the Vaca Mountains down to Solano County and has native coldwater fishes including chinook salmon, rainbow trout, and steelhead.
But in the 1950s after Lake Berryessa was created, the native fishes began to rapidly decline, particularly anadromous fishes like salmon and steelhead, Rypel said. In addition, the prolonged drought in the 1990s caused large portions of Putah Creek to dry up, nearly driving the native fish to extinction.
The Putah Creek Council, UC Davis, and the city of Davis filed a lawsuit against Solano County’s water agencies and other cities. Farmers were accused of using too much water, and they were told to use less. But they said Monticello Dam, which created Lake Berryessa, decreased its water supply during times of drought, threatening their businesses and livelihood.
After 10 years, the result of the lawsuit was the Putah Creek Accord in 2000, which allowed for year-round water flows to prevent the creek from drying up and protect the habitat. Since then, the Solano County Water Agency, landowners, friends of the Putah Creek Council, and other organizations have tried to restore the creek by adding water back to increase the flows. A new “streamkeeper” position was created to monitor and manage the creek while coordinating with students and other stakeholders to restore the body of water.
“When I got to Davis in 2017, for the few years prior to that, there had been all of a sudden ... a handful of salmon that were showing up in the fall. Never a lot, just a handful,” Rypel said. “And basically what happened during my time over the last eight years was that every year the numbers kept increasing.”
People found out that almost all of them were coming from the federal hatcheries or state hatcheries around the area. Usually, juvenile salmon migrate to the ocean to live as adults and swim back to fresh water to spawn.
In 2017, graduate student Lauren G. Hitt and other researchers started looking at the carcasses found along the creek to see where the salmon had been.
“We had figured this out because the hatcheries put little tags in a [portion] of the fish that lets you know where they came from. But we had also done some otolith microchemistry,” said Rypel, who explained that otoliths are the little ear bones that allow fish to find their balance in water. “Those little bones also lay down rings, just like trees do. So you can tell how old they are, and then the chemistry of that material also basically tells you where they were in that year of life.”
Researchers monitored adult chinook salmon in Lower Putah Creek every year on a weekly basis between October and January. They conducted surveys in the upstream-to-downstream direction and counted the number of both live and dead salmon. Each carcass was recorded with a GPS. They looked at the otoliths, measuring and observing them under a stereomicroscope to see the annual growth rings.
One of the challenges in restoring the creek and increasing the salmon population is bringing enough cold water, which comes from Lake Berryessa and tends to warm up as it flows downstream. For big reservoirs, cold water resides at the bottom while warm water is on top.
“It’s been, I think, a great success story of how we can have salmon on the landscape, but also agriculture and people and cities, and … to me, it’s a real California story,” said Rypel.
In fall 2024, researchers counted a total of 735 spawning adults in Putah Creek, compared to the handful counted in 2017.
Other areas are also making efforts to increase the salmon population amid similar water usage conflicts.
Under the new plan, diversions would be limited to between 50 percent and 70 percent at certain times of the year.
The Modesto Irrigation District previously told The Epoch Times in an email that the plan would impact the local farming community and others who rely on the water. It stated that long-term impacts will include reduced affordability of locally grown food, lower-quality drinking water, and burdens on disadvantaged communities.
San Francisco’s public utilities commission, the third largest supplier in California, argued that the plan could cause user water shortages.
Both sides are trying to find a balance between maintaining water supplies for agriculture and urban users, and protecting and promoting the wildlife environment.
