Operating Shasta in a New Climate

Moving from crisis management to long-term stability

Purpose

Shasta Reservoir is the centerpiece of the Central Valley Project - a major infrastructure component with effects reaching far beyond its confines in the upper Sacramento Valley. As the Bureau of Reclamation undertakes reinitation of consultation on the new operation of the Central Valley Project and State Water Project under the Endangered Species Act, Reclamation would like to engage with interested parties and the public as part of a multilayered and multifaceted effort to envision a modernized Shasta Reservoir that operates within a different environment than which existed almost 80 years ago.


Introduction

A Northern California icon, Shasta Dam and Reservoir are at a crossroads as Reclamation readies a new set of operating criteria for the Central Valley Project. The dramatic and widespread effects of California’s recent drought have called into question the many purposes the reservoir serves and the need to forge revised rules that reflect the likelihood of further harsh conditions and the need to respond with resolve and equanimity. 

Aerial view looking down over a dam, reservoir, and river with a blue sky and mountains.
Aerial view looking down over a dam, reservoir, and river with a blue sky and mountains.

It’s one of the most impressive public works projects ever built. It transformed the future of California, moving billions of gallons of water to farms and people each year. Almost 80 years after its completion, Shasta Dam and Reservoir remain the backbone of the Central Valley Project."

-- Ernest Conant, Regional Director, California-Great Basin, Bureau of Reclamation

Click play and unmute to watch introductory video.

Water releases from Shasta Reservoir fulfill several obligations and responsibilities, such as necessary instream flows to the Sacramento River, flood management, ecosystem support, deliveries to farms and wildlife refuges, hydropower production, and, in tandem with the State Water Project's Lake Oroville, helping to maintain water quality standards in the Sacramento-San Joaquin Delta.

A dry lake with exposed shorelines and mountainous terrain.

But the California of the 21st century is much different and complex place than what existed when Shasta was unveiled in the depths of the Second World War. Climate change has pushed an already volatile weather pattern into a more variable and more demanding realm.  

A black and white photograph of a major dam under construction.

Extreme heat saps the soil of needed moisture, reducing runoff and creating tinderboxes for wildfire.

A distant mountain range is engulfed in a cloud of smoke from a forest fire.

Less snowpack puts a greater pressure on reservoir storage. Creeping sea level rise means more water releases are needed to address salinity in the Sacramento-San Joaquin Bay-Delta, which provides critical water supply for the Bay Area. 

Given the worst aspects of climate change, experts believe Shasta’s operation must change if it is to continue meeting the needs of people and the environment. The alternative is a grim reality marked by conditions that favor neither water users nor the environment. To succeed, some hard decisions await. 


A System Challenged by Change

With a storage capacity of about 4.5 million acre-feet, Shasta is dwarfed by its cousins on the Colorado River, Lake Powell and Lake Mead, which have a combined storage capacity of about 50 million acre-feet of water. Unlike those reservoirs, which are heavily dependent on snowpack, Shasta is primarily fed by runoff from rainfall.

In most years, Shasta fills and makes required releases as multiple storm systems roll through the region between fall and spring. To achieve the greatest benefit from its temperature control device that keeps the downstream river nice and chilly for fish, the optimal reservoir storage should be 3.8 million acre-feet to 4.5 million acre-feet of water as the year transitions to warmer months and the demand for supplies increases.   

Every drop of water in the reservoir is accounted for, whether it is flows for the Sacramento River, allocations to senior water rights, allocations for other irrigation and municipal contractors, or water quality preservation 200 miles downstream. There are many demands on the water from Shasta, and it must operate within strict enviromental parameters, making hard choices for water managers. It is susceptible to the harshest effects of drought, with impacts visible after only two dry years.

Drought is a regular occurrence in California, where the margin between wet and dry years means the difference between reservoirs filled to the top or struggling to hold water in the early fall.  

The lack of available water for irrigation in 2022 was a disaster. It's clear we must take all possible measures to prevent a reoccurrence or at least do everything we can to mitigate that impact on our family farms, our communities, and our environment." 

-- Donald Bransford, owner of Bransford Farms

A dry field and trees in the background.

Climate change has super charged the impact of the state’s extreme weather events, with prolonged, hotter droughts and intense storm events that can flood wide swaths of low-lying areas. 

The consequences are broad and unambiguous: rising sea levels mean more storage is needed to repel salinity in the Delta. Drought combined with hotter temperatures mean a larger cold-water pool is needed to help maintain winter-run Chinook and other species survival. At times, there simply isn’t enough water to go around. 

A woman speaking.

The existing paradigm is not built for reliability or resilience. Kristin White, Reclamation’s Deputy Regional Director for Operations, said the increasing intensity and severity of California's dry periods “has led us to re-think how we operate Shasta Reservoir to get through these droughts … benefit from the wetter years [and] have a more predictable and reliable outcome coming out of drought where there is a lot more certainty of what to expect.” 

That means finding ways to ensure there is enough water left in the reservoir when the wet days of winter are a distant memory. 

“That additional storage gives us more flexibility to manage for ecosystems and endangered species, agricultural water deliveries as well as municipal and industrial water supply,” White said, adding that having the water available “gives us maximum flexibility to address all of those areas in a more predictable manner that people can start planning for as soon as the signs start showing that we are in fact going into a drought.” 


Salmon in the Spotlight

Adequate water quality conditions are critical for the recovery and resilience of the endangered winter-run Chinook salmon that return to the Sacramento River each summer to spawn.

Fish swimming together.

The Sacramento River winter-run Chinook salmon are found nowhere else in the world. Prior to the construction of Shasta Dam, they migrated to spawn in the headwaters of the Sacramento, Pit, and McCloud rivers, and Battle Creek. Today, one remaining population spawns in the Sacramento River below Keswick Dam.

A dam with rushing water and power lines.

Winter-run Chinook evolved spawning in the cold, spring-fed rivers high above Shasta, but now their survival is largely contingent on water released from Shasta Dam.

Successfully managing water temperatures is a critical component to the survival of fish on their journey through the Sacramento River to spawn, incubate, and migrate as juveniles towards the ocean to mature.

Salmon eggs need cold, clean water throughout incubation, and winter-run Chinook spawn in the gravel beds of the Sacramento River during the hottest months of the year. When enough cold water is not available, such as during droughts, warmer stream temperatures can lead to egg mortality and fewer baby salmon. When the dry years pile up, the effect of their population numbers is profound.

"While winter-run Chinook salmon are one of the best studied fish species in the Central Valley, estimates of temperature-dependent mortality of eggs and young fish reflect field monitoring of other life stages," said Josh Israel, science division manager with Reclamation's Bay-Delta Office. "The information we have about environmental factors influencing incubating winter-run Chinook salmon eggs and fry is limited and there remains more to learn about egg and fry mortality."

Fish eggs collected in a tray.

The devastating effects to winter-run Chinook caused by drought, combined with the dwindling numbers of returning fish, have sparked a sense of urgency by federal and state agencies, their tribal partners, and other interested parties. They've undertaken extraordinary actions to protect, preserve and possibly expand the population of the species, from the installation of water chilling units at Livingston Stone National Fish Hatchery to the  reintroduction of salmon eggs  in the McCloud River above Shasta Reservoir.

Reclamation Supervisory Mechanical Engineer David Klipp talks about the Chillers at Livingston Stone in July 2022


The Way Forward

The Shasta Reservoir of 1945 dramatically reshaped California’s water supply portfolio, tapping into the vast watersheds of the north for the benefit of people hundreds of miles away in the Bay Area and the fertile San Joaquin Valley. For decades the crown jewel of the Central Valley Project worked wonders and secured California’s place as a global supplier of agricultural products. 

That paradigm has given way to one that features increasing climate extremes and a dramatically slimmer margin between wet and dry years. Responding to the challenge requires a planning strategy that anticipates worst-case scenarios without compromising the many benefits of the Central Valley Project. It’s not a de facto proposition and will require nimble maneuvering if adverse circumstances are to be avoided. 

People talking.

In her  April 26, 2023, testimony  to Congress, Reclamation Commissioner Camille Calimlim Touton portrayed a scenario that demands a reassessment of the agency’s water supply management.   

“Climate change has made it likely that we will continue to experience the same, or worse, hydrology in the future,” she said. The reprieve offered by the bountiful rain and snow in the West “is an opportunity to get ahead of the planning.” 

A woman speaks into a microphone.

Climate change has made it likely that we will continue to experience the same, or worse, hydrology in the future... The reprieve offered by the bountiful rain and snow in the West is an opportunity to get ahead of the planning."

-- Camille Calimlim Touton, Commissioner, Bureau of Reclamation

The stakes are critical. Winter-run Chinook salmon are struggling to survive. The lack of available water in 2022 devastated Sacramento Valley farmers, communities, birds, and other species. It’s clear continuation of the status quo is not an option. 

Tractors plow dry soil with mountains in the background.

Given that, experts believe the Shasta of the future cannot be swung by dramatic changes to its water supply. That means limiting the inefficiencies of spilling water if the next year is wet, honing measures to protect fish with drought response and maintaining the cold-water pool and overall storage volume if the following year is dry. 

It also means working with senior water rights holders to find the means to take preemptive actions to alleviate the most egregious consequences of future droughts. 

Undertaking such significant change to Shasta’s operation must be done with respect and accordance to a variety of statutory, regulatory and contractual obligations."

-- Ernest Conant, Regional Director, California-Great Basin, Bureau of Reclamation


Taking Action

Drought is a slow-moving disaster. It evades easy responses, instead requiring a robust and ready-made response strategy that uses all the tools federal, state and local officials have at their disposal – water conservation, water quality standards, drought barriers and forbearance agreements with senior water rights holders. 

One way to manage through future droughts is adoption of the so-called “Victorian Objectives,” a pursuit developed by Australian officials during their Millenium Drought. A conservative, preventative approach, the Victorian Objectives designate current hydrology (drought, dry, average, wet, very wet) and plan appropriate responses that lessen the brunt on the environment and water users.  

“Our adaptive management approach is based on shared risk across entitlement holders, including the environment, across different climate scenarios,” said Andrew Sharpe, executive manager with the Victorian Enviromental Water Holder in East Melbourne. 

Other approaches include adjusting operations to achieve the most beneficial tradeoffs in water use, reducing deliveries to users at critical times, transfers, and boosting production at the Livingston Stone National Fish Hatchery. 

Looking ahead, more engagement in a science and fish monitoring program could accelerate implementation and improve the current understanding of how fish respond to changing conditions in the riverine environment and address conditions beyond water management alone.

Two people hold fishing nets in a shallow river.

It’s clear the Shasta Dam and Reservoir are called upon to meet the societal and environmental needs that were not contemplated three generations ago. The recent droughts, while painful, are but a small measure of longer, more intense drought episodes from long ago that peek at us through the portal of tree ring data and other measuring means. A comprehensive management framework for Shasta is vastly preferable to an approach that merely tries to get along year to year. 

Establishing a revamped management approach for Shasta requires careful analysis, collaboration, impartiality, and cooperation. Some believe the water storage and delivery system is broken. Others say a renewed spirit of dedication and creativity can get the job done, perhaps through the implementation of emerging voluntary agreements that seek to maximize the combined benefit of enhanced instream flows and habitat restoration. Emerging, cutting-edge science is crucial to future management. 

What’s clear is the need to modify Shasta’s operations in a way that avoids the crisis conditions experienced during the driest three-year period on record. 

“Generally, the expected result is that we get through droughts better than we got through the last one. What we hope is the actions that we've crafted are going to lead us to Shasta Reservoir being higher if went through similar droughts than what we’ve seen in the past.”

-- Kristin White, Deputy Regional Director of Operations, California-Great Basin, Bureau of Reclamation


What's Next

Changing the way Shasta Dam and Reservoir are operated is a monumental initiative underscored by a system in crisis. No one agency can be the torchbearer. It will take a combined effort from all who depend upon a vibrant and reliable Shasta to ensure available water and a stable environment. 

It’s a task that requires meaningful dialogue, skillful maneuvering and adaptive management. It is not a sweeping, top-down endeavor but a concentrated, measured effort, that, like the construction of the dam itself, must be achieved with clear objectives and milestones. The work is just beginning.   

 

A large dam and river with a mountain and tree-lined hills.

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Logos of major government agencies.

Acknowledgements

We would like to thank all of our partner agencies: California Department of Water Resources, U.S. Fish and Wildlife Service, NOAA Fisheries, and the California Department of Fish and Wildlife. 

We would also like to thank the following contributors that supplied photo and video resources: The Yurok Tribe, California Department of Water Resources, Reclamation Fish Biologist John Hannon, and Reclamation Project Manager Amy Holland.

Conceived, written and produced by Gary Pitzer, Tara Jane Miranda Campbell and Aric Coppola.

Bureau of Reclamation

California-Great Basin 2023