TWELVE
The Hydraulic Era
SALMON AND DAMS
Wild salmon are survivors—living through volcanic eruptions, ice ages, mountain building, fires, floods, and droughts. I feel certain they will persist if we can control our behavior and give back what we’ve taken from them—rivers that retain some of their healthy ecological function.
JIM LICHATOWICH, Salmon without Rivers
THE TWENTIETH CENTURY HAS BEEN called the “hydraulic era” in the American West. In fact, it took less than a century for water engineers, obsessed with providing enough water for an ever-growing population, to harness nearly every drop of naturally flowing water in California. Once sporadic and untamed, the water resources not only of the state but also throughout the American West were rapidly controlled, and the natural hydrology was re-engineered through massive public works including dams and aqueducts. Today, residents of the western states are linked to each other by an extensive web of aqueducts and pipes that bring them water every day. Dams are the modern solution to climate variability and unpredictability—trapping the water that falls during the winter months or melts in the spring, then storing and transporting that water to where it is needed during the drier summer and fall months. In addition to providing a steady flow of water to residents and agriculture, these water works also provide hydroelectric power and protection from flooding.
It has been argued that water engineering during the hydraulic era was a response to what water planners saw as a need to keep pace with a steadily increasing population and expanding agriculture across the American West. But others argue that the massive engineering of the region’s water resources was precisely what led to the rapid population growth, allowing it to grow to a size far larger than the region could support naturally.
Regardless of cause and effect with respect to population, the fact remains that the monumental changes to the region’s natural rivers, lakes, and wetlands have wreaked havoc on the natural aquatic ecosystems that these waters harbored. The plants and animals that depend on streams, lakes, and wetlands declined rapidly over the twentieth century due to large-scale land and water development in the West. Hundreds of species that are federally listed as threatened or endangered depend on rivers and streams. Over three-quarters of the native freshwater fish in the West are either extinct already or listed as endangered.
Human existence in the West relies not just on water resources but also on these other natural resources—the plants and animals—that the water sustains. The West is at a crossroads today as the human population in the region continues to increase, controlling ever more of the limited freshwater at the expense of aquatic ecosystems. Massive and profound as these public works are, they have been part of life in the West for so long that people are almost unaware of them. Few would voluntarily go back to the pre-hydraulic era, when water was unreliable from year to year and much of the agricultural industry would not have been possible. However, water development has come with a steep price to the environment—particularly to aquatic ecosystems—and the once-mighty salmon now serves as its poster child. In this chapter, we recount several of the events of the twentieth century that led to massive reconfigurations of water in California and discuss the impacts of water development on the state’s environment. We use the chinook, or king, salmon (Oncorhynchus tschawytscha)—a keystone species whose decimation over the past century has been closely linked to water development—to illustrate the effects of water development on aquatic ecosystems in general.
THE HYDRAULIC ERA BEGINS
During the westward push by pioneers in the early twentieth century, residents across much of the West experienced the region’s unpredictable climate, with its periodic droughts and floods, and set about taming the rivers. They dug canals to water their crops, in some instances using ancient Native American irrigation canals that had been preserved for centuries. As the population grew, these attempts to control the water expanded, ultimately leading to a total transformation of the natural hydrology of the region: water was stored and transported to whereever they wanted it, whenever they needed it.
FIGURE 30. Map of California showing aqueducts that bring water to Southern California, including the Los Angeles Aqueduct from the Owens Valley, the California Aqueduct from Northern California, and the Colorado River Aqueduct from the California-Arizona border. (Map redrawn by B. Lynn Ingram.)
In California, when people flocked to the abundant sunshine and mild climate of the southern part of the state, the lack of adequate water soon became apparent, particularly during periods of drought. The solution was to build the world’s largest and longest aqueduct for the time, diverting river water from the Owens Valley to Los Angeles, 230 miles south (see figure 30). The Los Angeles Aqueduct carried pristine Sierra Nevada snowmelt that fed the Owens River, water praised by John Muir, who wrote in 1901: “It is not only delightfully cool and bright, but brisk, sparkling, exhilarating and so positively delicious to the taste that a party of friends and I led to it twenty five years ago still praise it, and refer to it as ‘that wonderful champagne water;’ though, comparatively, the finest wine is a coarse and vulgar drink” (p. 185).
As it turned out, only a small amount of this pristine water was actually used by Los Angeles residents for drinking. Most of that “wonderful champagne water” was used to irrigate orchards, fill swimming pools, and water lawns, gardens, and palm trees planted by the city in its effort to transform this semiarid Southern Californian desert into an empire.
The Owens Valley water project set the tone for the water battles that followed in the twentieth century. Disputes erupted between the Owens Valley farmers, who were eventually ruined as their water disappeared, and the rapidly expanding city of Los Angeles. Major environmental impacts resulted, including the disappearance of Owens Lake, which lay at the southern end of the Owens River, in 1924. For millennia, this ancient lake had been large (twelve miles by eight miles) and had served as an important nesting and feeding stopover point for millions of waterfowl along the Pacific Flyway. When the lake completely dried up in the 1920s, 108 square miles of dry lakebed, including a mixture of evaporite minerals (those that precipitate from the dissolved salts in the evaporating water), sand, and clay, were exposed to erosion. Winds blowing in the region generated great alkali dust storms, leading to poor air quality. The Owens Valley was rapidly converted from the lush agricultural region the pioneers had created back into a semi-arid desert with grasses and shrubs—albeit one without a river running through it.
Two decades later, Southern California again looked far afield for more water to meet its growing population: this time the Colorado River was to be its new water source. The 1931 propaganda film “Thirst” aimed to convince voters to approve bonds to build another aqueduct that would ultimately bring water to Los Angeles from the Colorado River. In this movie, the chairman of the Metropolitan Water District of Southern California narrates:
All of Southern California was at one time a desert waste. We have reclaimed this desert and now we have in its place this growing empire. But the desert is ever around us, waiting and eager to take back what was once its own. And it will take it back, unless we bring in more water. Unless we take immediate steps to bring in water from an outside source, the people of Southern California will be up against a serious water shortage. But we’re fortunate at having within our reach a water source capable of supplying our needs. This source is the Colorado River. We must not think that this is something for the future; it is of the most immediate and pressing necessity. If we are to survive and to grow, we must have the water that will enable us to maintain our mastery over the desert.
The film goes on to describe the region’s rapidly declining water table, the result of more groundwater being pumped out of the ground than could be replenished by rain and runoff. The region was pumping an estimated 170 million gallons of groundwater per day. It was said, however, that the Colorado River could provide one billion gallons of water per day—over six times the amount they actually needed at the time. It is not surprising, then, that during California’s prolonged and deep Dust Bowl drought voters approved a bond to fund the 242-mile Colorado River Aqueduct, which was completed in 1941.
In Northern California, the city of San Francisco began looking eastward to the Sierra Nevada for a more reliable source of water in the early twentieth century. The city set its sights on the Tuolumne River and proposed to dam the Hetch Hetchy Valley in Yosemite National Park. A battle between the Sierra Club (led by John Muir) and the city of San Francisco (with Gifford Pinchot, the first chief of the U.S. Forest Service) lasted between 1902 and 1913. In 1913, the city was authorized to build a dam on the Tuolumne River, transforming the Hetch Hetchy Valley into a large reservoir for San Francisco and other Bay Area cities—a project that would not be fully completed until 1934.
Two decades later, the California Aqueduct was built to bring water from the wetter northern half of California to the San Joaquin Valley and Los Angeles. This project was part of the larger “Central Valley Project” funded by the Roosevelt administration during the Great Depression. These twentieth-century water projects led to a population explosion in California, from 500,000 in 1920 to over 37 million in 2012.
In the Southwest, much of its population growth would not have been possible if not for water development, particularly of the Colorado River. The Colorado drains rain and meltwater from states in its upper drainage basin—Wyoming, Colorado, Utah, and New Mexico—and brings this water into the deserts of the lower basin, including Nevada, Arizona, and California (see figure 31). In the past, it was a capricious river: a sleepy stream one day but (following a winter storm or a summer monsoon downpour) a raging torrent the next.
The taming of the Colorado River began with the construction of Hoover Dam in the 1930s, followed by numerous other dam projects on the Colorado in the following decades. These water projects have reduced devastating flash floods but have also decimated the native fish species that were adapted to the natural conditions on the river. The Colorado now provides water and hydropower for the largest cities in the West: Phoenix, Las Vegas, Denver, Los Angeles, and San Diego.
FIGURE 31. Map of the southwestern United States showing the Colorado River and its drainage basin (shaded region). (Map redrawn by B. Lynn Ingram.)
Every California river has at least one dam, and many have more than one, with 1,500 dams in this state alone. The reservoirs behind these dams hold almost 42 million acre-feet of water, which is about 60 percent of the state’s total yearly river runoff. Throughout the twentieth century, enormous water projects were built by federal and state governments in California, including the Central Valley Project, the State Water Project, San Francisco’s Hetch Hetchy Project, the Sacramento–San Joaquin Flood Control Project, the Colorado River Aqueduct, and Los Angeles’s Owens Valley Project. Water is captured and stored in reservoirs, then transported from the snow-capped Sierra Nevada range to the drier Central Valley farmlands and Southern Californian cities, where about 60 percent of the population lives. This “water on demand,” in addition to extremely fertile soils, has transformed California’s Central Valley into the “bread basket of the world”—growing 55 percent of America’s produce.
The twentieth-century era of dam construction eventually came to an end in the 1970s as the environmental impacts of water development could no longer be ignored. The extensive system of dams and aqueducts in the American West had been built when the interconnections between waterways and the ecosystems they support were poorly understood and not yet in the popular press. Since then, research and restoration has begun in an attempt to save aquatic ecosystems that are on the verge of collapse. Today, the flows left in rivers to restore aquatic ecosystems—dubbed “environmental flows”—are a hotly debated topic between farmers, fishermen, environmentalists, and scientists.
Healthy watersheds—and the ecosystems they support—go largely unappreciated because they lack a market value. Nevertheless, rivers provide food, materials, and recreation, and freshwater ecosystems regulate environmental conditions that benefit humans. For instance, wetlands improve water quality by filtering out pollutants and impurities, and they provide an important buffer during periods of flooding.
ENVIRONMENTAL COSTS OF THE HYDRAULIC ERA
Declining diversity in freshwater habitats in the western United States is largely a result of the combined effects of natural hydrologic patterns, pollution, and nonnative species invasions. In California, fish provide the best indicators of aquatic deterioration. Of the 129 native fish species in the state, 40 percent are in decline, 37 percent are eligible for listing as threatened or endangered, and 5 percent are extinct. Most of these species (60 percent) are found exclusively in California, so their decline is thought to be due to factors within the state, directly related to water and land development.
The Salmon Story
The plight of the once prolific salmon on the Pacific coast illustrates the impact of water development on aquatic life. Salmon have important linkages with many ecosystems from the ocean to streams and are therefore considered a keystone species. The chinook salmon have evolved along with western watersheds over thousands to millions of years and have been a mainstay of coastal Native American diets for at least five millennia. Although natural population sizes of salmon have fluctuated over this time period, at no point in the past have their numbers dropped as low as they have over the past century.
The natural range of chinook salmon encompasses the northern Pacific Ocean from California to the Gulf of Alaska and includes entire watersheds of the western states: from the rain forests of the Cascades in the Northwest to the Sierra Nevada range and deserts of California and as far inland as Rocky Mountain streams. Salmon by the millions once migrated up rivers along the Pacific coast, transforming streams into sparkling “silver pavement.”
In his book King of Fish: The Thousand-Year Run of Salmon, geomorphologist David Montgomery at the University of Washington describes how salmon migration patterns and speciation co-evolved with the geomorphology of western North America over the past twenty million years. During this time, the plateau between the Rocky Mountains and the Pacific fragmented into the fault-blocked basin and range topography in Nevada, while the mountain ranges along the Pacific coast, from California to Alaska, were uplifted. These topographic changes inland and along the coast formed many disconnected watersheds with distinct stream conditions. The isolation of these streams eventually led to the evolution of different salmon species.
For many millennia, the streams and rivers of these coastal watersheds have provided breeding grounds for the salmon. Hatching in the cold, rapidly running mountain streams, the young salmon fry develop into juvenile salmon and then make their way downstream and eventually out to sea. There, they spend their adult years in the open waters of the Pacific before beginning their arduous and improbable return-migration to their ancestral streams, where they lay their eggs in the cold water and gravel beds before they die. How they accomplish this remains to some extent a mystery, but these faithful fish are emblematic of the interconnectedness of conditions in the oceans, in the climate, and on land.
The Climate Connection
Salmon populations have fluctuated in response to climate change over the northern Pacific Ocean operating on a variety of timescales. When sea surface temperatures are unusually cold off the coast of the Pacific Northwest, the upwelling of nutrient-rich waters enhances the growth of phytoplankton and krill, allowing salmon populations to do well. During periods when reduced upwelling leads to higher surface water temperatures, krill and phytoplankton decrease, leaving less food for salmon and causing a decline in their populations.
Nate Mantua, a climatologist at the University of Washington in Seattle, has shown, with his colleagues, that salmon population size changed in Alaska and the Pacific Northwest in response to ocean conditions over the past century. They demonstrated that North Pacific sea surface temperatures were generally warmer from 1925 to 1947 and again from 1977 to 2000; between 1947 and 1977 and again after about 2000, sea surface temperatures were generally cooler. These shifts in ocean conditions are part of the Pacific Decadal Oscillation discussed in previous chapters. Here, we note simply that this climatic shift, or oscillation, has had direct effects on salmon productivity throughout this vast region.
Salmon populations have also responded to broader climatic shifts on longer timescales—like those described in chapters 9 and 10. For instance, a study looking at the chemistry in sediments cored from a Kodiak Island lake in Alaska has documented shifts in salmon abundance over the past two thousand years. During the three to five years that adult salmon spend in the ocean, they assimilate an isotope of nitrogen (nitrogen-15) in their tissues that is unique to the marine environment. After the salmon migrate back into the watershed (in this case, they migrate up the rivers into a lake), the nitrogen-15 from their tissues ends up in the lake sediments after the fish die and decompose. Analyses of nitrogen-15 in the lake sediments collected in layers provide a measure of the amount of salmon entering the lake from the ocean over time. The lake sediment cores reveal a pattern of fluctuating populations, with a low abundance of Alaskan salmon prior to AD 800, then increasing from AD 800 to 1200, and decreasing again after AD 1200. This pattern correlates with climate changes over the American West. During the Medieval Climate Anomaly (discussed in chapters 9 and 11), ocean surface temperatures off the coast were more often cooler than usual; these data correlate with a period of greater abundance of salmon as seen in the lake sediments. Subsequently, the isotope data in the lake sediments indicate that salmon populations dropped during the Little Ice Age, a time when ocean temperatures were often unusually warm, with frequent and intense El Niño events (see chapters 10 and 11).
Despite the natural fluctuations in salmon abundance associated with changing climatic conditions, salmon have been a mainstay for Native American populations along the Pacific coast for at least 5,000 years. Many tribes today still consider salmon critical for their survival as a culture and a people. The relationship between these tribes and salmon along the Pacific coast evolved as salmon habitats and annual runs became more stable and abundant during the mid-Holocene, when sea levels stabilized following the last ice age (as described in chapter 7). The native people understood the salmon’s natural migration patterns and managed for a sustainable harvest, using barbed spears, harpoons, dip nets, and seine nets. Prior to European contact, Native Americans in California each year caught and consumed an estimated 15 million pounds of salmon. Farther north, on the Columbia River, a population of 50,000 Native Americans harvested between 20 and 40 million pounds of salmon annually—representing about 5–20 percent of the annual salmon runs, depending on yearly variability in salmon populations. These harvests did not seriously affect the salmon over the thousands of years that humans have lived along the Pacific Coast. Yet now, over the past century, the salmon along the West Coast have almost disappeared.
Causes of Salmon Declines
Today, salmon are at the center of some of the most contentious environmental battles in the West, all swirling around water and land development. The steady decline of the salmon along the West Coast began in the mid–nineteenth century, when pioneers settled the region and began altering the landscape. In California, hydraulic gold mining was the first major assault on migrating salmon. Streams were choked with sediment that was washed out of the Sierra Nevada foothills by enormous hoses. Moreover, commercial fishing of salmon began in rivers in the 1860s and in the ocean in the 1890s. But it was the twentieth-century era of dam building, the hydraulic era, that had the greatest impact on salmon populations, reducing them to a small fraction of their former levels. Other factors affecting the salmon—such as logging and cattle grazing in the watersheds, pollution from abandoned mines, gravel mining in streams, overfishing in the ocean, and periods of natural climate variability with unusually warm ocean conditions—have also contributed to their plight. But all of these factors combined are thought to have played only a minor role compared with the severe impacts of dam building on West Coast rivers.
Dams physically block salmon migration, preventing the fish from reaching their spawning habitat, and this is thought to be the primary cause of salmon decline. In California, juvenile salmon that manage to reach the Sacramento–San Joaquin Delta and the San Francisco Bay often fail to reach the ocean because many are entrained in the huge battery of pumps in the southern delta that transport water to the California Aqueduct and down to the San Joaquin Valley and Southern California (see figure 30). The small juveniles have evolved to follow the currents, and these pumps have reversed the currents in the delta to flow south, away from the estuary and the Pacific Ocean. Millions of salmon fingerlings are lost each year, sucked into the pumps and killed, decimating future salmon populations. In addition, the delta pumps draw a greater proportion of river water during droughts, when farmers have a greater demand for water, leading to even higher fish mortality during an already stressful time.
Although salmon populations have fluctuated over time as part of natural cycles, their numbers have reached an all-time low over the past several decades. Fisheries biologist Jim Lichatowich writes in his book Salmon without Rivers:
The salmon are among the oldest natives of the Pacific Northwest, and over millions of years they learned to inhabit and use nearly all the region’s freshwater, estuarine, and marine habitats. Chinook salmon, for example, thrive in streams flowing through rain forests as well as through deserts; they spawn in tributaries just a few miles from the sea and in Rocky Mountain streams 900 miles from saltwater. From a mountaintop where an eagle carries a salmon carcass to feed its young, out to the distant oceanic waters of the California current and the Alaskan Gyre, the salmon have penetrated the Northwest to an extent unmatched by any other animal. They are like silver threads woven deep into the fabric of the Northwest ecosystem. The decline of salmon to the brink of extinction is a clear sign of serious problems. The beautiful ecological tapestry that northwesterners call home is unraveling; its silver threads are frayed and broken. (p. 6)
In many ways, the salmon in Pacific coastal rivers reflect the health of the entire watershed: their decline is a warning sign that these ecosystems are suffering. The chinook salmon experienced unprecedented declines from 2006 to 2011, when their numbers dropped so low that the entire salmon fishery from the northern Oregon border to Mexico was closed in 2008 and 2009 and was severely restricted in 2010.
The coping strategies developed by salmon, dubbed the “portfolio effect,” have allowed salmon from California to Alaska to survive for millions of years. Salmon hatcheries may produce more juveniles, but they have been unable to overcome the obstacles and habitat destruction that has accompanied water development in the West.
California’s Central Valley: Disappearing Wetlands and Lakes
Another poignant example of the environmental price of water development is the disappearance of enormous expanses of wetlands in California’s Central Valley, including three enormous lakes that were located in the southern end of central California. A century ago, California’s vast Central Valley would change seasonally as precipitation and river flows changed. This expanse of grassland dotted with oak trees in the dry summer season would be transformed into lush wetlands and marshes during the wet winter season as the rivers, including the Sacramento and San Joaquin, drained the Sierra Nevada and overtopped their natural levees. Large trees—sycamores, willows, cottonwoods, and oaks—once grew along these rivers in abundance. The Central Valley was also home to prolific wildlife: grizzly bears, antelope, Tule elk, salmon, and millions of migratory birds along the Pacific Flyway during the winter, including pelicans, geese, ducks, and cranes.
Although hunting, fishing, and other activities took a heavy toll on the wildlife there throughout the late nineteenth and early twentieth centuries, heavier impacts to wetlands began during the mid- to late nineteenth century as settlers were encouraged to drain and reclaim these “unproductive” wetlands. The catastrophic 1861–62 floods, and large floods that followed, prompted landowners in the Central Valley to begin small-scale land reclamation and flood control measures. But the greatest blow to wetlands of the Central Valley resulted from the era of dam building in the twentieth century, particularly the Central Valley Project in the late 1930s. These water projects, including the building of levees along the Sacramento and San Joaquin rivers and their tributaries, prevented winter and spring floodwaters from spreading out into their natural floodplains, destroying wetlands, shallow lakes, and habitats for fish and wildlife.
The Central Valley once contained four to five million acres of wetlands; by the late twentieth century, only 400,000 acres remained. As the wetlands disappeared, so did the wildlife that depended on them, including the wintering waterfowl—from tens of millions in the 1940s to only about three-and-a-half million by the end of the twentieth century.
Particularly heartbreaking was the fate of the three ancient lakes—Buena Vista, Tulare, and Kern—in the southern end of the Central Valley. These lakes, and the wetlands between them, formed the most extensive contiguous region of wetland in California, covering an estimated 500,000 acres. Tulare was at one time the largest freshwater lake west of the Great Lakes, with four times the surface area of Lake Tahoe. Dating of sediments cored from the Tulare Basin shows that the lake formed over a million years ago, making it one of the oldest lakes in California. These three lakes and their wetlands hosted an incredible diversity of wildlife, with thousands of wild horse, elk, antelope, deer, grizzly and brown bear, wolf, coyote, ocelot, lion, wildcat, beaver, and fox. Birds numbered in the millions, including ducks, swans, marsh wrens, rails, and geese, using the lakes as a stopover point along the Pacific Flyway. Tulare Lake also hosted the southernmost run of chinook salmon in the United States.
The wetlands between these lakes were initially filled in (“reclaimed”) following the winter of 1861–62, after the series of severe atmospheric-river storms that generated floods submerging the entire Central Valley (see chapter 2). More serious impacts on the lakes began in the early twentieth century, when the rivers that fed them (the Kern, Tule, Kings, and Kaweah) were diverted to irrigate crops in the Central Valley. What had been the source of water for these great lakes for over a million years was cut off, and the lakes dried up completely. The wildlife that made this region home was lost along with the water. The remaining dry lakebeds were then ploughed and planted with crops, primarily cotton. As a final irony, these crops had to be irrigated with the very river waters that had been diverted from the lakes in the first place. Today, it is difficult to find even the remnants of these ancient lakes within the expanse of crops in the southern San Joaquin Valley.
The Colorado River and Delta
Elsewhere in the West, water development similarly took place without any consideration for the ecological consequences for rivers and their watersheds, floodplains, or deltas. On the Colorado River and its major tributaries, for instance, aquatic ecosystems began declining in the decades after Hoover Dam and fifty-seven other major dams were built on the river and its tributaries starting in the 1930s. Important features of the Colorado River were altered after the construction of these dams, which hold back warm, sediment-laden water, and these sediments then settle out of the still water behind them. At the same time, the deeper parts of the reservoirs become cooler without direct heat from the sun. Thus, the water that is released from the dams to the river downstream is clearer and much cooler than the natural Colorado River water (warm and muddy) to which the native fish species had been accustomed for millennia. All of the 35 species of fish that evolved in the Colorado River—including minnows, chubs, and suckers—suffered from the changing environmental conditions after dams were built.
The Colorado River delta has also been decimated from dam construction and water diversion. The Colorado reaches its delta just south of the Mexican border, where it then empties into the Gulf of California. There, the impacts of damming and water diversions are perhaps the most severe—but least apparent. Before entering the gulf today, only a trickle of the Colorado River remains, and, at times, especially during the dry years, the river no longer reaches its natural delta. Historically, this extensive delta covered about two million acres of woodlands, wetlands, and deserts. In the 1920s, naturalist Aldo Leopold paddled through the “endless green lagoons” (p. 150) of the Colorado River delta to the Gulf of California. Yet today, 93 percent of the delta’s wetlands and woodlands have been reduced to a barren, unproductive mudflat.
Major impacts are felt even beyond the delta, in the Gulf of California itself, where the Colorado River once emptied, bringing nutrients, freshwater, and sediments and supporting a prolific marine ecosystem. Freshwater and saltwater mixed in this region for thousands of years, forming rich nursery grounds for fish, shrimp, and waterfowl. But, along with the Colorado River, marine life in the northern Gulf of California has suffered a major decline. Researchers at the University of Arizona have studied changes in the abundance of the Colorado delta clam (Mulinia coloradoensis), a species that once flourished at the outlet of the Colorado River in the gulf. These clams provide a measure of ecosystem health, and research shows that, a thousand years ago, these clams were at least twenty times more abundant in the Gulf of California than they are today.
The Sacramento–San Joaquin Delta
The Sacramento–San Joaquin Delta is the hub of California’s water distribution system and has been at the center of controversy among environmentalists, farms, fishermen, and cities in the state for four decades. Once a 700,000-acre tidal freshwater marsh, the delta has been gradually converted into a network of channels and islands that limit fish habitat. Moreover, rivers upstream have been impounded behind reservoirs and diverted for agriculture and cities, causing further declines in the delta’s habitats. Pumping of water in the southern delta to the San Joaquin Valley farms and Southern California via the California Aqueduct has caused currents in the delta to reverse toward the south, rather than flowing west into the San Francisco Bay and out the Golden Gate. These currents pull small fish toward the southern delta, entraining and killing thousands of endangered delta smelt and juvenile chinook salmon. The delta smelt is endemic to the delta and has been declining since 1990. After 2000, the smelt declined even further as pumping through the delta increased.
In the early 1980s, one proposed solution to these problems was the Peripheral Canal, a forty-three-mile, concrete-lined channel that would have linked the Sacramento River directly to the California Aqueduct. In 1982, however, voters—divided along geographic lines with those in the south voting in favor and those in the north voting against—rejected the construction of this canal. Yet the idea of a canal or tunnel is being reconsidered today, and its proponents argue that it would allow for water exports to the south without the harmful pumping of water in the southern delta. A tunnel, they say, would also protect the delta from seawater intrusion should an earthquake breach the levees protecting this water source. Those opposed to the tunnel are concerned that it would allow for the diversion of too much water away from the delta and the San Francisco Bay estuary, causing increased salinity and further ecosystem declines.
We now understand the impacts that water development has had, and continues to have, on the natural environment and wildlife in the western United States. Policymakers have begun to restore water resources and aquatic habitats, which means that all of us must make water conservation an even higher priority, realizing that we must share this life-giving resource with the natural world. This will be even more imperative in the future, since our water resources may be further taxed as global warming brings changes in climate, sea level, and the hydrologic cycle. This topic is the focus of the next chapter.