Central Valley Project
Based on Wikipedia: Central Valley Project
In 1969, more than 117,000 winter Chinook salmon swam up California's rivers to spawn. By 2017, that number had collapsed to just 1,123—the second-lowest count since modern tracking began. The story of how one of the world's most abundant fish populations crashed is, in many ways, the story of the Central Valley Project itself: a monument to human ambition that transformed California into an agricultural powerhouse while unraveling ecosystems that had thrived for millennia.
The Great Thirst
California's Central Valley is a geological paradox. This vast depression—stretching 450 miles from Redding in the north to Bakersfield in the south—contains some of the most fertile soil on Earth. The problem is water, or rather, the maddening distribution of it.
The Sacramento Valley in the north receives between 60 and 75 percent of all precipitation that falls in the entire Central Valley. The San Joaquin Valley to the south, despite being much larger, gets only about 25 percent. This wasn't a problem for the Indigenous peoples who lived there for thousands of years. They adapted to the Mediterranean climate with its bone-dry summers and wet winters, building hunter-gatherer societies that worked with the land's natural rhythms.
The Spanish colonial period introduced cattle ranching and the mission system, built on the forced labor of California's native tribes. But even the Spanish model of grazing livestock largely accommodated the land's natural limitations.
Everything changed with the Gold Rush of 1848.
Newcomers and Old Problems
After gold fever swept through California, settlers stayed to farm. Most had come from places with reliable summer rainfall. They looked at the rich soil and assumed they could grow anything. They were half right.
Large cattle ranchers soon dominated the landscape. Henry Miller, the most successful of them, eventually controlled 22,000 square miles—an area larger than Massachusetts, Connecticut, and Rhode Island combined. Chinese workers built levees along the Sacramento-San Joaquin Delta, creating the first irrigated orchards in the region.
But ordinary farmers discovered a harsh reality. The Sacramento Valley flooded with punishing regularity each spring. The San Joaquin Valley, meanwhile, was essentially a semi-arid desert. Cities drawing water from the delta found their supply inadequate during the dry months. The dream of California as an agricultural paradise seemed destined to remain just that—a dream.
Unless someone could figure out how to move water from where it fell to where it was needed.
Eighty Years of Political Warfare
The first serious proposal for what would become the Central Valley Project appeared in 1873, when Barton S. Alexander completed a report for the United States Army Corps of Engineers. The concept was simple in principle but staggering in execution: capture water in the wet north and transport it to the dry south through a vast network of dams, canals, and pumping stations.
The Bureau of Reclamation—the federal agency responsible for managing water in the American West—showed interest as early as 1904 but made little progress. A series of devastating droughts in the early 1920s finally created the political will for action.
In 1933, California passed the Central Valley Project Act, authorizing the sale of revenue bonds to raise $170 million. Then the Great Depression intervened. With the state treasury empty, California turned to the federal government for help. What followed was a bureaucratic shuffle as the project bounced between state and federal control, between the Bureau of Reclamation and the Army Corps of Engineers.
The battles weren't just administrative. The Central Valley Project became a proxy war over California's future. Large landowners fought small farmers. Private power companies battled advocates of public utilities. Irrigation districts clashed over water rights. Indigenous communities, whose ancestral lands would be flooded by new reservoirs, had essentially no voice in the process.
Environmental concerns were largely ignored. The dominant question was not whether to transform California's waterways, but how.
Roosevelt's Colossus
Construction finally began in earnest during Franklin D. Roosevelt's New Deal, making the Central Valley Project one of the largest public works initiatives of the era. When completed, it would be the world's biggest water and power project—a title it held for decades.
The system that emerged is almost incomprehensibly vast. Twenty dams and reservoirs store about 13 million acre-feet of water. (An acre-foot is roughly 326,000 gallons—enough to cover a football field to a depth of about one foot. Thirteen million acre-feet would flood the entire state of Connecticut to a depth of three feet.) Each year, about 7.4 million acre-feet flows through the project's canals and aqueducts.
Shasta Dam, the system's centerpiece, rises 602 feet above the Sacramento River north of Redding. Behind it lies Shasta Lake, capable of holding over 4.5 million acre-feet of water. The dam generates 680 megawatts of electricity—enough to power half a million homes.
But Shasta Dam was just the beginning.
The Plumbing of California
Understanding the Central Valley Project requires thinking of California as a massive hydraulic machine. Water enters the system from three main sources: the Sacramento River, the Trinity River, and the American River. Through an elaborate series of diversions, tunnels, and canals, this water is captured, stored, and redirected across hundreds of miles.
The Trinity River Division exemplifies the project's ambition. The Trinity River flows toward the Pacific Ocean, its watershed entirely separate from the Sacramento's. Engineers built Trinity Dam to create Trinity Lake, the project's second-largest reservoir. From there, water travels through the Clear Creek Tunnel to Whiskeytown Lake, then through the Spring Creek Tunnel to Keswick Reservoir, generating 474 megawatts of power along the way. Finally, this diverted Trinity water joins the Sacramento River—a different watershed entirely.
It's as if engineers had surgically connected the circulatory systems of two separate organisms.
The American River Division, located east of Sacramento, adds another layer of complexity. Folsom Dam—famous to many as the site of a state prison—stores over a million acre-feet in Folsom Lake while generating 200 megawatts of power. Eight additional earthen dams prevent the reservoir from spilling over its natural boundaries. Downstream, Nimbus Dam regulates the flow and powers the Nimbus Fish Hatchery, an attempt to compensate for the destruction of natural spawning grounds.
Where the Water Goes
The Sacramento Canals Division takes water from the Sacramento River and distributes it through a web of smaller canals and pumping stations. The Tehama-Colusa Canal stretches 110 miles. The Corning Canal adds another 21 miles. Together with various diversion dams and pump plants, this network irrigates about 100,000 acres while supplying municipal water to communities throughout the region.
But the longest journey belongs to water destined for the San Joaquin Valley.
Water from Shasta Lake flows down the Sacramento River to the Sacramento-San Joaquin Delta, where freshwater from California's interior meets salt water from San Francisco Bay. Before the Central Valley Project, this mixing zone shifted seasonally—salt water pushing inland during dry months when river flows dropped.
Now, controlled releases from Shasta and other reservoirs keep the salt water at bay, protecting both farmland and drinking water supplies. At the delta, some water is diverted into the Delta-Mendota Canal, which carries it southward through the San Joaquin Valley. Along the way, it fills San Luis Reservoir (shared with California's separate State Water Project) and eventually reaches the San Joaquin River at Mendota Pool.
Meanwhile, Friant Dam on the San Joaquin River diverts that river's natural flow into canals heading even farther south, to the Tulare Lake basin and as far as the Kern River. The system essentially hijacks two rivers—the Sacramento and the San Joaquin—and redistributes their water across an area larger than many countries.
The Transformation
The results were extraordinary. Five million acre-feet of water now irrigates three million acres of farmland annually. Another 600,000 acre-feet supplies cities and towns. California agriculture, made possible largely by the Central Valley Project and its state-run counterpart, now accounts for about seven percent of California's gross state product.
The semi-arid desert of the San Joaquin Valley became one of the most productive agricultural regions on Earth. Cities that would have been constrained by their water supplies grew into major metropolitan areas. Spring floods that had devastated Sacramento Valley communities for generations came under control.
And the hydroelectric capacity—over 2,000 megawatts—helped power California's postwar industrial boom without burning fossil fuels.
By almost any economic measure, the Central Valley Project succeeded beyond its planners' wildest dreams.
The Price
But nature keeps its own accounts.
The salmon were the first obvious casualties. Chinook salmon had evolved over millions of years to navigate California's rivers, swimming upstream to spawn in cold mountain streams, their offspring riding the current back to the ocean. Dams blocked these ancient migration routes. Water diversions left rivers too shallow, too warm, or simply dry. Hatcheries could breed fish, but they couldn't replicate the genetic diversity and resilience that wild populations had developed over countless generations.
The winter Chinook run—the salmon that spawn in the cold waters below Shasta Dam—fell from over 117,000 fish in 1969 to barely a thousand by 2017. The fall run in the Klamath and Trinity rivers collapsed so completely in 2017 that California and Oregon declared a fisheries disaster. Commercial fishing operations that had sustained coastal communities for generations found themselves with nothing to catch.
Riparian zones—the ecologically rich corridors along riverbanks—shrank or disappeared entirely. Wetlands that had served as nurseries for countless species dried up. The delta's delicate ecosystem, caught between salt water and fresh, struggled to maintain balance as water managers pulled ever more flow from the system.
Historical sites and Native American tribal lands vanished beneath the rising waters of new reservoirs. Communities that had existed for centuries were simply drowned.
And then there was the pollution. Intensive irrigation doesn't just deliver water to crops; it also carries away whatever the water touches. Agricultural runoff laden with pesticides, fertilizers, and dissolved salts flowed into rivers and seeped into groundwater. The Spring Creek Debris Dam, built in 1963, exists solely to prevent acid mine drainage from the Iron Mountain Mine from poisoning the Sacramento River—a problem that had nothing to do with the Central Valley Project but was made worse by altered river flows.
The Reckoning
By the 1990s, the environmental costs had become impossible to ignore. Congress passed the Central Valley Project Improvement Act in 1992, mandating that 800,000 acre-feet of water annually be released into rivers and wetlands to meet state and federal ecological standards. The Refuge Water Supply Program and other initiatives attempted to restore some of what had been lost.
Then came the Endangered Species Act.
The delta smelt, a small fish found only in the Sacramento-San Joaquin Delta, became a symbol of the conflict between agricultural water use and environmental protection. When surveys found no smelt in the delta for two consecutive years—2019 and 2020—it signaled that even the adapted, degraded ecosystem that had replaced the original was now failing.
Regulatory decisions based on endangered species protections forced the Bureau of Reclamation to reduce water deliveries to parts of the San Joaquin Valley. Farmers who had built their operations around assured water supplies suddenly faced devastating shortages. The same infrastructure that had made the valley bloom now couldn't deliver what it had promised.
In February 2020, President Trump signed new federal biological opinions—essentially, determinations about how much water could be diverted without driving endangered species to extinction. Later that month, seventy-five project customers, including the massive Westlands Water District, received permanent federal water contracts, cementing their legal right to Central Valley Project water even as the biological reality of providing that water grew increasingly uncertain.
The Unfinished Project
Some elements of the Central Valley Project were never completed. The Auburn-Folsom South Unit includes several planned dams that remain unbuilt. Other features were partially constructed before funding or political support evaporated.
These incomplete pieces hint at an alternate history—a Central Valley Project even larger and more transformative than what exists today. They also represent a kind of geological bookmark, a point where California's ambitions finally exceeded what even the federal government could finance or justify.
Today, the Central Valley Project operates in an uncomfortable middle ground. It remains essential infrastructure, supplying water to millions of acres of farmland and hundreds of thousands of people. Its hydroelectric plants generate carbon-free electricity. Its dams prevent the catastrophic flooding that once made parts of the valley uninhabitable.
But it can no longer pretend that its operations come without cost. Every acre-foot delivered to a farm is an acre-foot not flowing through a river. Every dam that generates power also blocks salmon from reaching their ancestral spawning grounds. Every diversion that makes agriculture possible in one place makes ecosystems impossible in another.
The Shape of Scarcity
California's Mediterranean climate hasn't changed. Wet winters still alternate with dry summers. Droughts still arrive in cycles, as they have for millennia. What has changed is the number of demands on a finite water supply.
The Central Valley Project was designed for a California of 7 million people. Today, nearly 40 million live in the state. Agricultural productivity has increased far beyond 1930s projections. Environmental awareness has transformed from an afterthought into a legal mandate. Climate change has begun altering the timing and quantity of precipitation in ways that twentieth-century engineers never anticipated.
The project's twenty dams still stand. Its canals still carry water across hundreds of miles. Its turbines still spin, generating power for the Western grid. But the confident optimism that built this system—the belief that human engineering could simply override natural limits—has given way to harder questions about allocation, sustainability, and justice.
Those 117,000 salmon that swam up California's rivers in 1969 didn't know they were living in the last years of abundance. They were following patterns older than human civilization, responding to cues written into their DNA across countless generations. Now their descendants, the 1,123 that returned in 2017, carry the genetic legacy of catastrophic population collapse—bottlenecked, vulnerable, and dependent on human decisions for their survival.
In that sense, the salmon and the farmers now have something in common. Both inherited a system they didn't create, both depend on water that someone else controls, and both face a future shaped by choices made decades ago by people who couldn't imagine how those choices would compound.
The Central Valley Project was the world's largest water and power project when it was built. It transformed California and helped create the modern American economy. It also set in motion consequences that will take generations to fully understand—let alone resolve.
That's the thing about moving rivers. The water goes where you send it, but the effects flow in directions no one predicted.