Will California Save the Last Winter Run Salmon This Year?

California’s State Water Board can save this year’s population of endangered winter run chinook salmon eggs and fry from cooking to death in too-hot river temperatures, as the fish did in 2014 and 2015. And they can improve the chances for later-spawning fall run chinook— the backbone of the salmon fishery—to survive below Shasta Dam as well. But they have to act now.

New modeling from the National Marine Fisheries Service shows that, if the State Water Board fails to act, and the U.S. Bureau of Reclamation operates Shasta Dam as it plans to this year, about 80% of endangered winter run salmon will die from temperature-dependent mortality alone:

In reality, this level of temperature-dependent egg mortality means that the entire year’s cohort of wild winter run chinook will likely die before reaching the ocean this year. We’ve seen this movie before—in 2014, when winter run suffered 77% temperature-dependent egg mortality, over 94% of the entire juvenile population died before reaching Red Bluff Diversion Dam—and that’s before additional mortality as they migrate down the Sacramento River to the Delta and then to the ocean. Similarly, in 2015, when 85% of the endangered winter run was killed by lethal water temperatures at the egg, only 4.5% survived to Red Bluff—meaning more than 95% of the entire year class was killed before migrating half way to the Delta. And it wasn’t just the endangered winter-run; lethal water temperatures also devastated the fall run Chinook salmon that spawned in the Sacramento River, with the U.S. Fish and Wildlife Service estimating that 97.7% of them were killed upstream of Red Bluff Diversion Dam.

The experience of 2014 and 2015 nearly caused the extinction of wild winter-run chinook and the population has not yet recovered. This critically endangered species certainly can’t take another year of near-total mortality of an entire year of baby salmon. And while salmon fishermen face a severely restricted fishing season this year to protect salmon stocks, the Bureau of Reclamation’s planned operations of Shasta would slaughter the fall run Chinook salmon upon which fishermen rely.  

The good news is that we know how to do better. All it takes is for California’s State Water Board to act now to direct the Bureau of Reclamation to reduce water releases and operate Shasta Dam according to model runs that reduce temperature-dependent mortality to an estimated 50%—still not ideal, but much better than 80%. Here are the results of those runs:

The main difference between these two model runs is that the Bureau of Reclamation would not be permitted to drain Shasta Dam in the latter to deliver water to its irrigation contractors. In the first modeling run shown above, water released from Shasta Dam (shown on the graph with the y axis labeled “Keswick Discharge (TCFS)”) spike up to an average of 9,000 cubic feet per second (cfs) in June, 10,000 cfs in July, and 8,000 cfs in August. That water is almost exclusively released for delivery to irrigation water contractors on the Sacramento River above Sacramento.  Doing so drains water storage in Shasta, with end of September storage at less than 1 million acre feet of water, which is likely to be catastrophic if 2022 is dry.

In the second modeling run shown above, releases from Shasta are reduced to 6,000 cfs in June and held there through August. Reducing those releases increases the amount of cold water that is retained in Shasta and allows that water to be used to cool river temperatures when winter run chinook eggs and fry need it to survive, from June to the end of September. That is why temperature-dependent mortality estimates fall to 50% in this run. This approach also maintains more cold water in Shasta reservoir at the end of September that can be used to help cool fall run eggs and fry in October, if air temperatures remain warm, and increases end of September storage to 1.4 million acre feet, providing some insurance in case 2022 is also dry.

The Bureau of Reclamation and DWR are currently delivering millions of acre feet of water to water contractors at the expense of meeting their obligations to the public under the terms of their water rights. That’s true in the Delta, where the CVP and SWP are violating water quality standards, and it’s true at Shasta Dam.

The State Water Board has the authority and the mandate to protect California’s native fish from being slaughtered at the hands of a water rights holder like the Bureau of Reclamation. It has failed over the  last two decades to protect the Delta Smelt, a unique species found only in California’s Bay-Delta estuary, that has declined from a population in the millions to a mere two fish found in the last six months. The State Water Board must not fail again and allow more extinctions of California’s native fish and wildlife to happen on its watch. The Board must act now to require Reclamation to reduce releases from Shasta Dam (and Keswick Dam) to a maximum of 6,000 cfs during the months of June through August to protect these public trust resources from a repeat of the devastation that they suffered in 2014 and 2015.

About the Authors

Kate Poole

Senior Director, Water Division, Nature Program

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