A couple of miles outside the town of Page, three 775-foot-tall caramel-colored smokestacks tower like sentries on the edge of northern Arizona’s sprawling red sandstone wilderness. At their base, the Navajo Generating Station, the West’s largest power-generating facility, thrums ceaselessly, like a beating heart.

Football-field-length conveyors constantly feed it piles of coal, hauled 78 miles by train from where huge shovels and mining equipment scraped it out of the ground shortly before. Then, like a medieval mortar and pestle machine, wheels crush the stone against a large bowl into a smooth powder that is sprayed into tremendous furnaces — some of the largest ever built. Those furnaces are stoked to 2,000 degrees, heating tubes of steam to produce enough pressure to drive an 80-ton rod of steel to spin faster than the speed of sound, converting the heat of the fires into electricity.

The power generated enables a modern wonder. It drives a set of pumps 325 miles down the Colorado River that heave trillions of gallons of water out of the river and send it shooting over mountains and through canals. That water — lifted 3,000 vertical feet and carried 336 miles — has enabled the cities of Phoenix and Tucson to rapidly expand.

This achievement in moving water, however, is gained at an enormous cost. Every hour the Navajo’s generators spin, the plant spews more climate-warming gases into the atmosphere than almost any other single facility in the United States. Alone, it accounts for 29 percent of Arizona’s emissions from energy generation. The Navajo station’s infernos gobble 15 tons of coal each minute, 24 hours each day, every day.

At sunrise, a reddish-brown snake slithers across the sky as the burned coal sends out plumes of carbon dioxide, nitrogen oxide, mercury, lead and other metals. That malignant plume — containing 16 million tons of carbon dioxide every year — contributes to causing the very overheated weather, drought and dwindling flows of water the plant’s power is intended to relieve.

Its builders knew that the Navajo Generating Station, which began being constructed in 1969, would cause enormous pollution. An early government analysis warned that burning so much coal would degrade the region’s air by “orders of magnitude,” and federal scientists suggested Navajo and other coal plants in the region could turn the local terrain into a “national sacrifice area.” But for more than a decade, the pollution went largely unchecked. Climate change wasn’t yet a threat, and the other option for getting water into central Arizona — damming the Grand Canyon — seemed worse.

At times, officials have tried to mitigate the plant’s problems, pouring $420 million into improvements to limit sulfur dioxide emissions as acid rain blanketed parts of the country, for example.

But again and again, the federal government and the other agencies responsible for the plant have dodged calls to clean up the facility and have pushed some of the most stringent environmental requirements far into the future.

In a series of reports, ProPublica has examined how the West’s water crisis is as much a product of human error and hubris as it is of nature. The Navajo Generating Station is a monument to man’s outsized confidence that it would always be possible to engineer new solutions to an arid region’s environmental limits.

Now, 15 years into a historic drought, it is becoming increasingly clear that the era of engineering more and more water out of the Colorado River is coming to a close. The Navajo Generating Station is more a caution than a marvel, showing how much energy it takes to move water through an artificial river system, and the unforeseen damage produced by doing so.

The plant’s environmental toll is sure to fuel arguments for its eventual closing. For now, it has been granted a reprieve from complying with the Obama administration’s new Clean Power initiative, which requires Arizona to reduce its carbon output by 52 percent. But the Environmental Protection Agency has said that it expects to work with the Navajo tribe to reduce emissions separately from Arizona’s mandate, and will likely revisit that issue in the future. The plant will also soon be subject to a new federal environmental review process triggered by its renewed lease on Navajo lands.

To date, though, the Navajo has always found a way to survive as an essential piece of the infrastructure needed to tame the wild Colorado.

Last year, the plant’s owners and their supporters negotiated a compromise with the EPA that will allow it to continue operating until 2044.

“The mechanics of moving water is just lost on people,” said Jared Blumenfeld, administrator of the EPA’s region for the Pacific Southwest, including Arizona, Nevada and California. “It’s something that is just invisible. I don’t think people connect the dots on how enormous an undertaking it is to move water around, especially in a time of drought.”

It was with awesome feats of engineering that the West was built. To settle a vast, inhospitable region that lacked water, Americans harnessed the Colorado River — which tumbles 1,450 miles from the boulder-strewn flanks of the Rockies to the Sea of Cortez — and daringly used it to remake one-fifth of the country.

More than 100 dams were built across the system. Where the river’s path was inconvenient, its reach was extended with tentacles of tunnels and trenches deep into Southern California and Arizona. Parts of the river were even reversed; water sent eastward through pipelines beneath the Continental Divide. Each project was like a small surgery meant to strengthen and preserve the West’s access to the river before it was overused. And the more people who relied on the river, the more bandages and appendages engineers attached to it.

Over time, the engineers turned the river into one of the world’s largest plumbing systems, where a person and a button control even the wildest rapids in the Grand Canyon. The river’s tail waters have been allowed to flow their natural course into Mexico for just a few days out of the last 16 years.

The capacity to control a river — to tame its floods, to store its water so that it can be used even in drought and to displace it so that it can be streamed through the landscape for irrigation — is one of the greatest engineering advancements in modern civilization.

But as surging population, excessive demand for water, climate change and drought continue to menace the American West, the ability of mega-projects to sustain the same old patterns of consumption has diminished. The techniques used to extend the Colorado River’s vitality have instead begun to squeeze the life out of it.

It is not only the Navajo Generating Station — aging, polluting — that is so troubled. Many of the most significant pieces of infrastructure lose water, no longer function the way they were designed to as water levels drop, or have required hundreds of millions of dollars in fresh investments.

The Hoover Dam, completed in 1936, was erected to hold two years of river flow in reserve. Its walls stretch 1,200 feet across the Boulder Canyon, are 726 feet high and 660 feet thick. But today, the dam holds back lots of air, and less water, since the lake levels have dropped more than 140 feet from their high.

Lake Powell, which sits behind the 700-foot-tall Glen Canyon Dam and is the nation’s second-largest water reserve, is even more troubled. The lake has recently fluctuated between 39 and 51 percent full, and if the drought ended tomorrow, it could take nearly a decade for it to fill back up. But the larger problem is not that Lake Powell could one day approach what experts call “dead pool,” meaning there is no longer enough water for it to flow through the dam’s gates or generate the hydropower that the West’s electricity grid depends on.

It’s that the reservoir leaks like a sieve. As much as 123 billion gallons of water — 2.6 percent of the annual flow of the entire Colorado River — likely seeps into fissures in the porous sandstone underlying the lake and disappears each year, according to a 2013 study. Another 168 billion gallons evaporates off the surface annually, as the sprawling lake bakes in the arid desert climate. A facility whose central purpose is to save water instead loses a mind-boggling amount of it. Were Lake Powell to go away, the American Southwest would have approximately 6 percent more water overnight.

“There may well be an oncoming argument about whether we really ought to take that dam out,” said Bruce Babbitt, the former secretary of the interior and former governor of Arizona.

The river’s big canals have faced similar problems. The All-American Canal, an 80-mile aqueduct that ferries water along the north side of the Mexican border into California, recently received a nearly $300-million upgrade to stop some 22 billion gallons of water from seeping into the sand dunes beneath it each year.

“The vulnerabilities in this system are so numerous,” said Blumenfeld, the EPA official for several Western states. “When you look at the thousands of miles that water moves … the water loss is huge.”

This reckoning of the limits of American ingenuity to conquer the West was predicted more than 135 years ago, after John Wesley Powell first explored the river’s basin. Powell, who later ran the United States Geological Survey, assessed water supplies across the country for Congress. Though he had lost most of his right arm in the Battle of Shiloh, he rowed the Colorado River from Wyoming through the Grand Canyon, with 10 men in custom-made oak and pine boats he’d had sent from Chicago. Four of the men abandoned the expedition; three were killed by tribes as they hiked away from the canyon.

Powell, reporting afterward, told Congress about a bifurcated landscape: a river gushing and abundant, but relatively inaccessible, surrounded for hundreds of miles on all sides by a desert so devoid of rainfall and moisture that it almost certainly could not alone sustain efforts to grow food from its soil. “Many droughts will occur; many seasons in a long series will be fruitless,” he cautioned in a dour report. If one were to try to irrigate the desert, Powell warned, the infrastructure and facilities needed to do it would be so enormous and costly that only a large collective effort — like from the government — could pay for it.

What Powell wrote then could just as easily summarize what the Department of the Interior is relearning today. In 2012, the Bureau of Reclamation, in an unvarnished assessment of the West’s current water predicament, found the river outmatched by demand and implied that its water projects, by themselves, were no longer an adequate answer.

The best way to spread the region’s limited water supply further was to find ways to use it more efficiently, the agency concluded.

The Navajo Generating Station was born out of jealousy and Arizona’s great ambition. In 1901, Theodore Roosevelt declared, “The western half of the United States would sustain a population greater than that of our whole country today if the waters that now run to waste were saved and used for irrigation.” Roosevelt soon signed a law creating the Bureau of Reclamation and charged it with taking back the lands of the West from nature’s control.

Arizona coveted the thriving growth of Los Angeles but couldn’t keep California from hoarding water unless it had a way to take some for itself.

What Arizona wanted was a mega-canal — an artificial river that would pump one-tenth of the Colorado’s flow out of Lake Havasu, send it upward nearly the height of the Chrysler building and halfway across the state. The state’s business leaders didn’t just yearn for water. They envisioned their own thriving metropolises, kept cool in the scorching desert with air conditioning, lit bright and speckled with verdant golf courses and retirement villas. Such a vision would be possible only with lots of cheap power.

At first the Bureau of Reclamation proposed building two large hydropower-generating dams in the Grand Canyon, filling its majestic valleys to power Arizona’s canal. Environmentalists, though, ran newspaper ads comparing the plan to flooding the Sistine Chapel. The bureau needed an alternative.

Arizona, it turned out, had immense reserves of coal, most of it underlying the nation’s largest Indian reservation. A consortium of power companies had long been working toward what historians have called a “grand plan” to tap those coal reserves and generate the power to execute an expansive vision for Arizona and the rest of the West. In 1964, Time Magazine described the six-power-plant project as the world’s largest electricity complex, one that “would dwarf the TVA.”

The Navajo Generating Station promised to take the traditional coal plant and supersize it, employing state-of-the-art generators to produce 2,250 megawatts of power, more than all but a handful of the operating plants in the nation at the time.

The federal Bureau of Reclamation had never built a coal plant before, but it agreed to be the Navajo’s largest investor, taking a nearly 25 percent stake. The other investors included a number of Arizona utilities as well as the Los Angeles Department of Water and Power.

It all seemed a godsend. The Navajo plant would power Arizona’s big canal, the Central Arizona Project. The Native American tribes would get jobs. One of the world’s largest coal companies would mine the coal on the reservation, and a national construction firm would benefit, too. And the Southwest would get an abundant supply of homegrown energy that could support its expanding cities and cool them. The plan would even save the Grand Canyon.

“Back up and put yourself in that time frame,” said David Roberts, senior director of water resources for the Salt River Project, one of the station’s six co-owners and the operator of the plant. “It was a win-win for everyone.”

How the Navajo plant and Arizona’s water canal would pay for themselves, though, was based on a financially complex scheme, and everyone — from the federal government to Arizona’s water and power companies — had a stake. Almost none of it worked out as planned.

Most simply put, the Navajo plant — and all the pollution it caused — became a form of subsidy for cheap water. The Arizona authorities charged with selling the water in order to repay taxpayers scrambled for years just to break even, and their debt payment schedule to federal authorities is still significantly delayed.

“Financially, it wasn’t a wise decision,” said Douglas Kenney, director of the Western Water Policy Program at the University of Colorado Law School in Boulder.

For many, though, any financial setbacks mattered little when set against what the plant, the canal and the water it made available achieved: By 2010, Arizona had credited its water canal with nearly half of the state’s annual economic production.

“Monday morning quarterback all you want,” said the Salt River Project’s senior director of base load generation, Jim Pratt. The canal, Pratt said, “made Arizona, and the state has never looked back.”

Navajo turned out to be every bit as filthy as the government had warned in the 1970s, when officials predicted it would cause severe haze and health problems. The prized landscape that surrounds it, and the adjacent Four Corners region, has become significantly polluted, with 11 national parks and protected wilderness areas draped behind a curtain of smog. While no epidemiological studies have pinpointed a cause, EPA records include tribal complaints of a doubling in cancer rates in the Navajo Nation since the generating station began operating, as well as worsening asthma. The nonprofit environmental organization Clean Air Task Force estimated emissions from the Navajo plant alone were responsible for 12 premature deaths in 2012.

The EPA tried to clean up the site in the 1980s after environment groups sued — pressing for controversial emissions limits and forcing the plant, a decade later, to install expensive smokestacks that sharply reduced sulfur dioxide. But it wasn’t enough.

In 1999, the EPA tried to get serious again. Haze still veiled the national parks. The threat of climate change loomed on the horizon. The environmental tradeoffs that allowed the Navajo Generating plant to exist grew ever more dramatic.

The remaining problem was largely due to thousands of tons of nitrogen oxide that Navajo and other coal-fired plants still spewed into the atmosphere, pollution that wasn’t caught by the enormous filters installed to catch sulfur dioxide a few years before. The agency finalized a regional haze rule that aimed to restore all polluted areas — not just northern Arizona — to natural background levels of pollution. But Navajo, because it was so close to the Grand Canyon and other prized parks, would face some of the most stringent cuts.

Navajo’s owners, including both the Salt River Project and the Bureau of Reclamation, haggled with the EPA for years, suggesting alternatives and challenging the rules. But in 2009 the EPA announced its plans to force the Navajo Station into making dramatic cuts. In order to keep producing power, the agency wanted Navajo’s owners to install enormous catalytic converters that would scrub its emissions of nitrogen oxide and other pollutants, steps that would ultimately cut the plant’s most worrisome emissions by 84 percent and keeping some 28,500 tons of nitrogen oxide out of the atmosphere each year.

But in pushing for dramatic changes at the Navajo plant, the EPA underestimated how intertwined the plant had become with every aspect of life in the region — from providing its power to moving its water to buttressing the tribal economy.

The plant represented a herculean effort to solve the conflict between water and growth in the West. The EPA’s interference suggests that the consequences were too great. But Arizona and much of the broader region’s vitality had become dependent on the plant. It represented the core of the nation’s strategy to manage the most important resource for a significant chunk of the country’s economy. A seemingly simple aim of curbing pollution really suggested re-examining the larger system.

What the EPA really wanted, opponents claimed, was for the Navajo Generating Station’s owners to simply close up shop. After all, the EPA’s rulemaking process had led two other large coal plants in the region to shut down all or part of their operations.

“You don’t just close this power plant down,” said Jon Kyl, the former three-term senator and four-term congressman from Arizona who was closely involved in negotiations over the fate of the plant. “It will have an enormous impact on the entire fabric of the state of Arizona, not just because of power but because of water.”

The plant’s operators denied responsibility for the haze and claimed the fixes the EPA demanded would cost nearly $1 billion to implement. Such an expense, they argued, would cause electricity rates to skyrocket, doubling the cost of water delivered through the Central Arizona Project canal and threatening its viability. Where else would the canal, which depends on the Navajo station for more than 90 percent of its energy, get power?

Complicating any effort to recognize the plant’s problems was the fact that some of Arizona’s most influential leaders rejected the scientific consensus that the Navajo station’s carbon pollution played any role in a warming planet or intensifying drought.

Kyl, who was attuned to water scarcity issues and had sponsored several bills to address them, told ProPublica the link between the plant’s emissions and climate change “is absolutely not proven, it is simply assumed.”

As debate over the EPA’s plans meandered on, environmental groups made the case that the coal-fired Navajo was polluting the air and damaging people’s health.

“You are trying to raise your family in this environment, and you realize this is one of the top 10 dirtiest plants in the nation and it’s been spewing all this stuff for 40 years,” said Nicole Horseherder, a Navajo environmental activist. “Who is going to speak up and say, ‘Look, we are paying a huge cost so that the state of Arizona can have its profits, have its taxes, have its electricity, have its water?’ ”

Horseherder has twice testified before Congress about the power plant’s effects. Alongside groups like the Sierra Club, she urged legislators to replace coal with investment in new solar and other clean energy plants on the reservation.

Many of the strongest arguments for maintaining the Navajo as it was didn’t hold up to scrutiny.

The National Renewable Energy Laboratory, a division of the Department of Energy, analyzed the impacts of the EPA’s plan and found that power costs were unlikely to increase anywhere near as much as the plant owners insisted. “Could we have found the energy to move that water?” asked Tom McCann, Central Arizona Project’s deputy general manager of operations and maintenance, in an interview with ProPublica. “Yes.”

Finally, in July 2014, 15 years after the EPA formalized its haze rule and first set in motion rules that would curb nitrogen oxide pollution at the Navajo plant, a deal was finally struck to limit the plant’s harm.

But the deal, to many, was yet another compromise showing that the government was not yet prepared to adapt its power and water policies to a changing environmental reality.

The EPA had originally sought an 84 percent reduction in nitrogen oxide by 2018, swiftly curtailing the pollutant most linked to haze and health problems. Instead, the plant owners agreed to an 80 percent cut after 16 years, and to shut down one of its three generators for good by 2019, reducing overall emissions by one-third in the short term. They successfully put off installing new equipment to filter the two remaining smokestacks until 2030, a delay that would get the EPA much closer to its goals for nitrogen oxide in the long run, but allow the plant more flexibility. And the government agreed to allow the plant to continue operating until 2044.

The National Parks Conservation Association called the deal “unconscionable,” and other environmental groups also took note.

“They always get special bargains and deals,” Janette Brimmer, an attorney with Earthjustice, said of the Navajo’s long history with environmental regulators.

The EPA’s Blumenfeld insists the deal is better than it appears and that federal regulators achieved their most important goal of cutting nitrogen oxide by 80 percent while considering the complex employment and social needs of the region.

“You really can’t go and meet and talk to folks on the ground and understand all the issues and then say that the solution here was to shut it down. It would have been an absolute disaster,” Blumenfeld said. “It wasn’t balancing for balancing sake, it was wanting to get it right.”

On a morning last fall, Terry Edwards stood atop a waffled steel gangplank outside the humming heart of the Navajo Generating Station, 203 feet above the sprawling concrete yard. A rising breeze came off the desert as it heated in the bright sun.

Edwards, 58, with graying hair and metal-framed glasses, could almost see the town in Utah where he was born. He’d never strayed far, coming to work at the generating station in 1979, five years after it opened. Now he’s become an operations and maintenance supervisor and is accustomed to finding the most dramatic places in the facility to show off in a tour.

He calls the plant “Big Iron,” a nod to its central role in providing power to an entire region from a single plant. “We’re one of the cheapest suppliers of energy,” he said proudly. The coal is good quality, inexpensive and practically bottomless, he said, pointing down to a yard where miniature-looking trains pull up to the endless conveyors. It’s been moving like that every day for 40 years, he said, like a giant machine. And he thinks — though the feds estimate far less — that there’s another 200 years’ worth under the reservation.

Edwards has no qualms about the effect of burning all that coal on the drought or on climate change, which he said “is cyclical and man can’t change on his own.”

Even after the decadeslong debate over whether the plant’s contributions outweigh its harm, he has not reconsidered its purpose or wavered in his awe for what the generating station accomplishes, and he sees it as proof that man’s ability to conquer the West’s environment is as durable as ever.

The West is full of people like him. Indeed, as the region gets more crowded, drier and hotter, there is talk not of living within the current constraints but of engineering new ways to gather additional supplies of water. The West must continue to grow, Kyl says, or it will begin slipping backward. He thinks it will be necessary to shoot silver iodide into the clouds in an effort to make it rain or to build plants to desalt ocean water.

Some have proposed building a pipeline to route water 700 miles from the Mississippi River — or from its tributary the Missouri — to Colorado. Such a pipeline, like Arizona’s canal, would likely require yet another power plant to make it work. Others suggest towing icebergs down from the Arctic or filling tankers from Alaska’s rivers.

Though these ideas seem far-fetched, all are listed in the Bureau of Reclamation’s 2012 report on water shortages across the Colorado River basin and have been contemplated by some of the smartest policy experts in the nation.

Even if they remain out of reach, states are already racing to build billions of dollars of smaller engineering marvels in the hopes that machines and money can dig the West out of its drought.

Utah plans to dam its Bear River, at a cost of some $1.5 billion, and hopes to build a pipeline from Lake Powell, even as it runs dry. New Mexico plans to build a channel to divert water out of the Gila River before it crosses into Arizona, even though Arizona already uses much of that water. Colorado’s Legislature has discussed a plan to divert water from the Missouri River, at the far end of Kansas. California voters just passed a $7 billion water measure that amounts to a blank check but will likely be put toward new dams. The list goes on.

“Arizona will eventually have to bring water in,” said Kyl, who thinks the state has exhausted its other options. “When you cannot conserve any more and the demand exceeds the supply, you have to consider options.”

Environmentalists say it won’t work to spend new billions to add more bandages and appendages to the Colorado. The health of the river will get worse with each new diversion, they say, and the water wars between states will only intensify.

“Right now we have two colossal reservoirs and there isn’t enough water to keep even one of them full, and yet entities around the basin are trying to build more,” said Gary Wockner, executive director of Save the Colorado, an advocacy group. “They can pour more cement, but they can’t make it rain.”

Wockner and others say the elaborate projects built along the river amount to expensive distractions. The more permanent solution: Put the Colorado’s limited water to the best purpose, by planting more efficient crops, irrigating with modern equipment, writing laws that incentivize conservation, and reducing energy spent moving water over large distances.

“The Colorado River is already extremely depleted,” Wockner said. “There is nothing left to give, and it’s time to go to plan B, which is water conservation efficiency. It’s faster, cheaper and easier than building these new dams.”

As the debate continues and the water crisis deepens, the Navajo Generating Station keeps grinding away, consuming 22,000 tons of coal and emitting 44,000 tons of carbon each day, in large part to deliver Arizona’s water.

Naveena Sadasivam and Lauren Kirchner contributed to this story.