The 1st and 2nd Los Angeles Aqueducts in 2001. [Photo by Jet Lowe for the Historic American Engineering Record]
"Under no contingency does the natural face of Upper California appear susceptible of supporting a very large population: the country is hilly and mountainous; great dryness prevails during the summers, and occasionally excessive droughts parch up the soil for periods of 12 or 18 months. Only in the plains and valleys where streams are to be found, and even those will have to be watered by artificial irrigation, does there seem the hope of being sufficient tillable land to repay the husbandman and afford subsistence to inhabitants." 
So wrote Navy lieutenant Henry Augustus Wise, after spending considerable time in the Golden State in 1847. Although Lieutenant Wise would no doubt be surprised to know that California is now home to almost 40 million people, the fundamental water constraints that he described exist today. As Zev Yaroslavsky, a member of the Los Angeles County Board of Supervisors, put it: "Water is probably the single most vexing issue that we have in ... places like Southern California, because it's in such short supply. Water is a more valuable commodity in some respects than oil — or it will be over time." 
Indeed, metropolitan Los Angeles could not support a fraction of its current population without imported water, which today accounts for nearly three-quarters of supply. Water distribution and treatment alone account for about 18 percent of all energy consumed in the region, making it the invisible energy hog, rarely seen, poorly understood and ever on the verge of crisis.
Throughout the 19th century, settlement in California flourished as a result of gravity-fed irrigation. But by 1913 — when the Los Angeles Aqueduct was completed — all gravity-fed supply had been exploited. From then on Southern California water planners would look farther afield, at inter-basin transfer routes that would require uphill pumping. The first of these was the Colorado River Aqueduct, built in 1933, which carried California’s allotment of that river’s bounty from the Arizona border across 240 miles of scorching desert. But the most energy-hungry water project in the state — and among the most energy-intensive infrastructure projects on the planet — was the last of these aqueducts: the California State Water Project. To appreciate why it needs so much energy requires a brief lesson in California geography.
Top: The California Aqueduct begins at Clifton Court Forebay in the San Joaquin Delta. [Photo courtesy of the California Department of Water Resources] Bottom: Further south, the California Aqueduct crosses beneath the 1st Los Angeles Aqueduct. [Photo by Chris Austin]
Long before Hollywood Boulevard had its sidewalk stars or 90210 was a trendy ZIP code, the area that would become the Los Angeles Basin experienced some inconvenient geologic activity. A series of tectonic interactions between the Pacific and North American Plates — complicated by the San Andreas Fault — caused a chunk of the Earth's crust to compress and heave up, forming one of area's few east-west mountain ranges. Known to geologists as the Transverse Range, these mountains form a nearly 200-mile-long barrier. The topography does have advantages; it shelters Los Angeles from the desert to the east, and it's also provided, for the entertainment industry, a low-cost stand-in for the landscapes of Africa and Asia, not to mention Hazzard County, Georgia. But this barrier also separates Los Angeles from that part of the state where the water supply — from the western drainage of the Sierra Nevada Mountains — is most reliable. Vast quantities of water — most of it from snowmelt — flow westward from these mountains into the Central Valley. And located at the southern end of this valley, where the Transverse Range meets the Sierra Nevadas and the Coast Range, are the Tehachapi Mountains, which form an unavoidable barrier between Los Angeles and the ample runoff of the western Sierra Nevada.
Steepness and elevation make the Tehachapi Mountains a great place to ride a mountain bike, but a challenging barrier across which to deliver water. Using a system of gravity-fed siphons, as with the Los Angeles Aqueduct, would have been impossible: the grades are too steep for above-ground pipes to be fed by the gravity-powered action of siphons. Tunneling, which would have allowed gravity-powered siphons to function, is geologically infeasible in this seismically active zone. So Los Angeles had little choice. The only alternative has been to use energy to pump a river-sized aqueduct uphill and over the mountains. The resulting infrastructure — begun in the late 1950s under the auspices of the State Water Project, or SWP, and known as the California Aqueduct — would be not only the most massive infrastructural project in the state's history but also its single largest user of energy.
The 444-mile California Aqueduct works by pumping water uphill and then letting it flow downhill by gravity. It begins near sea level, pumping water from the Sacramento River Delta, near San Francisco; the water gradually climbs to the southern end of the Central Valley, at the base of the Tehachapis. In the course of this 278-mile section, 6 major pumping stations lift the water from sea level to an elevation of about 1,300 feet. Once the water reaches the mountains, the massive Edmonston Pumping Plant uses 9 gigantic pumps to lift the water a final 1,926 feet over the Tehachapi Mountains — after which point it can course leisurely downslope toward the faucets, fountains and swimming pools of Southern California.
Edmonston is one of the single biggest consumers of energy worldwide; the plant can pump an acre-foot of water (enough to supply one to three households yearly) in under 10 seconds, but to do so requires the rough equivalent of the energy in three 55-gallon fuel drums. In short, to get from the Sacramento River to the crest of the Tehachapi Mountains, one year’s worth of water requires just slightly less electricity than the combined amount used by all residences in the city of Los Angeles. While hydro-electric generators recover some energy as the water flows downhill after being pumped to the crest of the Tehachapis, this recovery accounts for only about one-quarter of total energy input. 
Left: Five of the 14 pumps at the Edmonston Pumping Plant. The 80,000-horsepower centrifugal pumps extend six floors below the blue tops visible here. Right: Cable trays run electrical wire at the plant. [Photos by Chris Austin]
In arid regions this is the difficult tradeoff: needed water is remote and heavy, and transporting heavy things long distances means using energy. Factor in mountainous landscapes, and the energy costs rise higher still. It's not surprising, then, that for the typical Southern California home, water delivery is the third biggest energy user, after air-conditioning and refrigeration.  In growing beyond the limits that could be supplied by a gravity-fed system, greater Los Angeles has bound its fate to the price of energy. When energy is expensive, water is expensive. Demand for water in the region now outstrips supply by about half the volume that Edmonston pumps yearly — an imbalance that has required conservation measures. And although demand for water is expected to increase significantly, the supply isn't likely to get larger. In fact, it’s likely to shrink as the impacts of global climate change intensify. 
Any attempt to address this dilemma through increased supply will be energy intensive: either water must be imported from even farther away (e.g., Oregon or Washington), requiring yet more pumps, or undrinkable water must be turned into drinkable water. Desalination, which turns seawater into freshwater and has been used widely in the Persian Gulf, is an extremely power-hungry technology; and even the most ambitious desalination plans would account for only 6 percent of California's freshwater supply.  Wastewater recycling, derided by its detractors as “toilet to tap," is another energy-hungry technology.
Today there is growing recognition that such dramatic strategies might not be needed if the emphasis shifted from supply to demand: if people simply used less. And there is some good news here: in the past 30 years, water use in Los Angeles has remained roughly constant, even as the population has grown by nearly one million.  Various tactics — such as restrictions on lawn watering, voluntary adaptation of low-flow showerheads and low-flush toilets, more aggressive pricing — have reduced per capita water consumption, and in the process saved large amounts of energy. Still, Los Angeles has a long way to go in terms of water conservation. At 168 gallons per day, the average L.A. household lags slightly behind Tucson, Phoenix and El Paso in terms of conservation, and far behind Germany, where the average household uses less than half as much. 
In the complex calculus of Southern California water, much has changed, and over time efficiency will surely increase. But all the while, as political leaders and utility managers grapple with the interrelationship of water and energy, there will remain, down an isolated service road at the base of the Transverse Range, a river in a pipe that is flowing uphill.
California Aqueduct at the Chrisman Pumping Plant, 13 miles before reaching the Edmonston Plant. [Photo courtesy of the California Department of Water Resources]
A few hundred miles away, the main aqueduct of the Central Arizona Project, the country's largest and most expensive water-delivery system, wends its solitary way through the blazing Arizona desert toward millions of homes, vast agricultural fields, low-slung silicon-chip plants, and Phoenix’s Wet’n’Wild waterpark. The CAP makes an eastward turn from the Colorado River’s Lake Havasu Reservoir not far from where California’s Colorado Aqueduct — one of three that supply the Los Angeles Basin — makes its westward turn. Between these two thirsty aqueducts — which provide irrigation for California’s Imperial Valley and municipal water for Las Vegas — it’s not surprising that by the time the 1,450-mile-long Colorado has reached the Gulf of California, the river is little more than a rivulet of toxic sludge.
In Arizona, water is such an emotional issue that at the end of a major drought in 1941, Governor Sidney Osborn declared April 26 a "Day of Thanksgiving for Water," complete with a chuck-wagon lunch and dancing in the streets of Phoenix.  The history of the water supply for Arizona’s two major cities, Phoenix and Tucson, has been a rollercoaster of abundance and scarcity. Large-scale water engineering is what makes it possible for people to inhabit this dry land; this has been true going back to the ancient Hohokam culture, which flourished from the 9th through the 14th centuries and then disappeared, most likely due to drought. One limitation faced by the Hohokam was that their water supply traveled by gravity alone.
Today gravity systems have been superseded by pumping technology. But coordinating population growth and water supply in Arizona has proven to be far more difficult than lifting water uphill. As Tucson and Phoenix have expanded, water infrastructure and population growth have chased each other in a cycle of ever increasing cost, dependency and vulnerability; as improved infrastructure allowed more reservoirs to be filled and more groundwater to be pumped, both in-migration and urbanization were spurred on. But southern Arizona’s climate is characterized by hard-to-predict cycles of drought; as population grows, the state needs ever-larger buffers against that uncertainty. As Charlie Ester, the Water Resource Manager for the Salt River Project, the utility that provides water for much of the metro Phoenix region, puts it: "If it does not rain every year, and reservoirs go dry, and there is nothing to pump, we're moving." 
Central Arizona Project system map. Click image to enlarge. [Via Central Arizona Project]
The Central Arizona Project is without doubt the apotheosis of this unfolding drama. In the decades before it was built, Phoenix depended largely on impounded surface waters stored in large reservoirs, while Tucson, with a much smaller watershed, depended on pumping groundwater from its sizable aquifer. By the 1920s, despite similarities in the overall quantities of municipal water, Phoenix’s reservoir system contained three thousand times more water than did Tucson’s. To meet demand, Tucson was pumping so much groundwater that by 1935 the city was dedicating between 65 and 75 percent of its electricity for this purpose; and by the early 1940s, it was removing groundwater at a rate faster than it could be recharged, leading to a lowering of the water table that would continue for decades.  By the early postwar years, all the "easy water" had been already appropriated and groundwater supplies were diminishing rapidly; on many occasions residents were asked to curtail water use, and in 1951 Phoenix supplies were so short that police patrols were dispatched to stop people from watering lawns or washing cars.  Thus it was abundantly clear that a massive project — on a scale that only the federal government could mount — would be needed to carry water from the Colorado River.
Authorized in 1968, begun in 1973, and completed in the early 1990s, the Central Arizona Project would become the icon of Arizona water supply, as well as one of the defining symbols of western water excess — the largest and most expensive water-transfer project ever undertaken in the United States.  Thanks to CAP, water falling as rain and snow in the Rockies as far north as Jackson, Wyoming, would now water the golf courses and fill the swimming pools of Tucson and Phoenix. In exchange, according to a schedule established in the enabling legislation, Arizona communities were expected to reduce their withdrawals of groundwater to prevent depletion of the aquifers.
The Central Arizona Project was intended to free southern Arizona from chronic water woes. But as with the California State Water Project, CAP has linked the supply of water to the price of energy. Also as in California, Arizona’s project is gravitationally challenged: 14 pumping stations are required to keep water moving along this 336-mile infrastructural straw, which includes a rise of 3,000-feet in its journey from Lake Havasu to southwest Tucson. Roughly one-quarter of the output of the Navajo Generating Station in Page, Arizona, is dedicated to this purpose. In one year the CAP’s pumps use the same amount of electricity as is consumed by about 210,000 typical Arizona homes. 
To some extent the yearly water bills for CAP customers reflect the price of moving water: For every dollar paid in household water bills, about 42 cents go to energy costs. But these surcharges have had minimal impact to date. According to journalist Shaun McKinnon, a reporter for the Arizona Republic, Phoenix residents still use water copiously, and the typical household water bill is lower than in many eastern cities. 
Central Arizona Project canal. [Photo by Tim Roberts Photography; used with permission from Shutterstock]
But all this could change soon. CAP and the communities it supplies are vulnerable to future increases in energy prices — even more so than in thirsty Southern California. Although CAP uses less power in aggregate than the California State Water Project, it uses more energy per capita; thus the risk and uncertainty of energy price spikes in Arizona are borne by fewer rate payers. And while the California State Water Project is powered by a diversified and less price-volatile energy portfolio, with hydro-electricity constituting the single largest energy source, CAP depends upon that single power plant in Page, which is fueled by coal.  Arizona, with much less precipitation and more rugged topography, and with no significant hydropower resources, has few options other than the Navajo Generating Station, located along the Utah border. This means that the future price of energy — and hence of water — is bound to the price of coal. Today that cost is relatively low. But decreasing supplies and, more important, tighter regulation of pollutants, including greenhouse gases, could dramatically change the equation. Under the most extreme scenario of cap-and-trade pricing for CO2 emissions, for instance, pumping costs could quadruple by 2030. 
Although rate increases would certainly pinch Arizona households (especially in Phoenix, where per capita water use is higher than in Tucson), the effects would likely not be dramatic, at least initially; any increases would be based on relatively low base prices, and households can usually adapt by changing exterior landscaping or taking shorter showers. For water-intensive industries, however, the margins are not so flexible. High-tech manufacturing has been one of the drivers of the Phoenix economy — enabling its great growth — but many of its industries have an insatiable thirst.
Intel, for example, has invested nearly $10 billion in the region and created more than 10,000 jobs in the Phoenix suburb of Chandler. There, where the subdivisions give way to scrub and saguaros, three silicon chip fabrication plants glisten in the sun, extending over the equivalent of 17 football fields. Making chips is a water intensive process, and this industrial campus consumes two million gallons daily (the plants actually require 7 million, but recycling reduces the net use). Intel is, in fact, the largest water consumer in town, although it pumps nearly three quarters of its wastewater (after purification) back into the aquifer, in effect banking it for the future.  This water supply comes at a significant energy cost: in addition to the energy used for pumping in and out of the aquifer, Intel’s water requires extensive filtration to achieve the purity level necessary for washing chips, a laborious process made more so by the mineral content of desert water.  With so much investment in this location, Intel seems unlikely to leave solely on account of rising water rates. But would the next Intel, scouting new locations, choose not to locate in Central Arizona due to concerns about the rising costs of water in an arid region? 
Central Arizona Project Pumping Plant #5. [Photo by Chris Austin]
The impact of rising energy prices on Arizona’s supply of affordable water will depend upon how much of that water is provided by CAP, relative to less energy-intensive sources. Currently, the typical CAP allocation of municipal supply ranges from 30 to 40 percent. But, as the Arizona Republic's McKinnon notes: “It only takes one or two dry years and the reservoirs can go down fast.” If the reservoirs drop, Phoenix will rely more heavily on the Central Arizona Project, and prices will reflect that. The conditions for the perfect desert storm that Phoenix officials fear most include prolonged drought (tree-ring records reveal that this has been common in the region over the centuries); increased CAP water rates due to drought and rising energy prices; and greenhouse gas legislation. Still worse would be prolonged drought throughout the Colorado Basin, which would reduce the volume of Colorado River water; among the southern basin signatories to the longstanding Colorado River Compact —which apportions the water among several U.S. state and Mexico — Arizona is lowest on the priority list. 
Ultimately, if western water becomes still more scarce and expensive, the region will need to negotiate a hard tradeoff between urban and agricultural users. For there is actually enough water in the West to keep people hydrated and clean, and maybe even to maintain green lawns and full swimming pools. But most water in the West is now used to irrigate crops; city dwellers get what’s left. And in these arid lands agriculture has been subsidized for decades through the provision of water below the cost of delivery. There may come a time when western water managers will need to ask whether desert agriculture — a vital source of America's food supply — is worth the cost.
Back in my office in Vermont, as I watch torrents of rain fall onto already saturated ground, I long for some droughty Southwestern weather. Vermont could hardly be more different from my birth state of California, at least with respect to water. Here in northern New England it rains so much that I didn’t water my lawn once this summer. Lake Champlain, into which most of Vermont’s water drains, contains over 20 million acre-feet — enough to supply greater Los Angeles for more than four years with no need to refill. And the nearby Great Lakes — with 20 percent of the freshwater on the planet (and 95 percent in the United States) — contain nearly a thousand times more water.
Clearly the real problem with water supply is less about scarcity than about distance and elevation; there’s plenty of water on the North American continent, but it requires extraordinary infrastructure and energy input to transport it from source to tap. A complicating factor is that sunshine attracts people, and in recent years the highest population growth rates have been in the Sun Belt — warm and dry regions tht are already at a hydrological breaking point.
Hinds Pumping Plant on the Colorado River Aqueduct lifts water through the Eagle Mountains. Click top image to enlarge. [Photos by Ron Gilbert]
But what does it mean to be water-rich? It's often assumed that east of the Great Plains, water is plentiful. This was true once, when populations were lower; but today parts of the Mid-Atlantic and Southeast verge on crisis. In 2007-08, the Southeast had such a prolonged and severe drought that boat launches in reservoirs wound up hundreds of feet from water lines, neighboring states battled over river allocations, and Georgia Governor Sonny Perdue called for a statewide "day of prayer for rain." Even Florida, once rich in freshwater habitat, is experiencing a crisis; with an astounding 90 percent of supply coming from pumped groundwater, the state is depleting its aquifers so fast that entire houses are being swallowed up by sinkholes as the ground subsides. 
Climate change will only complicate these problems. As global temperatures rise, we can expect to see more droughts, more evaporative losses in reservoirs and canals, and more expansion of the water-poor zone. Supplying thirsty cities will require ingenuity and conservation; it will also require more energy, because if supplies shrink, many cities will need to depend upon water basins farther afield. But at least, since the price of water remains low in most places — even in arid places — there is time to prepare.
There is another crucial climate-change variable in the water-energy nexus. Rising temperatures will likely cause rising sea levels. Low-lying coastal cities will need to undertake expensive public works projects to counter the effects of rising water tables and storm surges — and all such projects will require energy-hungry pumps. Already we’ve seen the impact of storm surges on New Orleans, much of which lies below sea level and where land is sinking almost an inch every two years. If sea levels rise, Katrina-like surges could become common. And as Katrina showed, even an extensive flood-protection system — New Orleans' network includes 148 large drainage pumps with a combined capacity greater than the flow of the Ohio River — can prove inadequate. In response to this failure, the Army Corps of Engineers has started to construct a $14 billion infrastructure system of levees, barriers, gates and flood pumps designed to withstand 16-foot storm surges. This project will require the world’s largest pumping station, a $500-million monster with the capacity to spew an astounding 150,000 gallons of water per second (or about 15 Olympic swimming pools per minute). It’s unclear exactly how much energy this will require; but there is no doubt that rising sea levels will mean rising energy needs. And so in New Orleans — and in low-lying coastal cities around the world — the management of water will be inextricably connected to the price of energy.
Aqüeducte de les Ferreres, Tarragona, Spain. [Photo by Joan Grífols]
Several years ago, when visiting Spain, I toured the bridge at Ferreres, built by the Romans during the reign of Augustus and located north of the Mediterranean city of Tarragona — a spectacularly preserved 250-meter-long segment of a 25-kilometer-long aqueduct. This ancient imperial construction underscores that water supply has always been fundamental to the establishment and prosperity of cities — and that water infrastructure, necessarily large-scale and sturdy, is often one of the most durable legacies of vanished civilizations. Roman engineering was indeed a marvel. The gravity-fed aqueducts of Rome supplied hundreds of thousands of citizens (in a city with high standards of personal cleanliness) with more than 250 gallons per person per day — more than some of America’s desert cities can feasibly provide today. And the Roman water-delivery system was so extensive that few inhabitants lived more than 50 meters from a water outlet. 
Two millennia later, many ancient Roman aqueducts remain serviceable (after some retrofitting). Operating with no external energy requirements, these brilliantly engineered channels functioned for centuries; in most cases they were vulnerable only to seismic activity — and eventually, of course, to conquest. But despite modern materials and engineering methods, the water delivery system of the American West is comparatively ephemeral — for the sole reason that it depends so heavily on energy. We have built major cities in response to the engineered availability of water, and we did so in an era when energy was cheap and apparently plentiful. But ultimately the price of energy might be as destructive to our public water supplies as invading barbarians were to Rome's.
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