High in the Rocky Mountains, snowmelt fills a stream that trickles down into Ohio Creek and then onward toward the Upper Gunnison River. From there, it tumbles through the chasms of the Black Canyon, joining the Colorado River, filling the giant Lake Powell reservoir, and, one day, flowing to Los Angeles.

But before the water gets more than a few miles off the mountain, much of this stream is diverted into dirt ditches used by ranchers along the Ohio Creek Valley. Standing astride one of those ditches one day last fall, Bill Ketterhagen dug his boot soles against the concrete edge of a 5-foot-wide dam. He spun a steel wheel and opened a gate that allowed water to pour into his fields of hay crops.

Ketterhagen, 39, manages a 750-acre ranch outside the town of Gunnison, Colorado, for its out-of-state owners, mostly growing a mixture of Meadow Foxtail, Timothy, wheat grasses and some alfalfa. The grasses, knee-high with bursts of clover flowers and flat, slender leaves, are cut, baled and shipped to feedlots where they fatten cattle soon to be slaughtered for beef.

Thickly built, wearing overalls and a four-day beard, Ketterhagen has a degree in biology and natural resource management and once worked in a division of the U.S. Department of Agriculture. He knows his fields could thrive with much smaller amounts of water — he’s seen them do so in dry years — but the property owners he works for have the legal right to take a large supply, and he applies the water generously.

“When we have it, we’ll use it,” he said. “You’ll open your head gate all the way and take as much as you can — whether you need it or not.”

Ketterhagen feels he has little choice. A vestige of 139-year-old water law pushes ranchers to use as much water as they possibly can, even during a drought. “Use it or lose it” clauses, as they are known, are common in state laws throughout the Colorado River basin and give the farmers, ranchers and governments holding water rights a powerful incentive to use more water than they need. Under the provisions of these measures, people who use less water than they are legally entitled to risk seeing their allotment slashed.

There are few starker examples of how man’s missteps and policies are contributing to the water shortage currently afflicting the western United States. In a series of reports, ProPublica is examining how decisions on water management and growth have exacerbated more than a decade of drought, bringing the West to the point of crisis. The Colorado River is the most important source of water for nearly 40 million people across California, Arizona, Nevada, New Mexico, Wyoming, Utah and Colorado, and supports some 15 percent of the nation’s food crops.

But the river is in trouble, and water laws are one significant cause. Legal water rights and state allocations have been issued for more water than the river, in an average year, can provide. Meanwhile its annual flow has been steadily decreasing as the climate changes and drought grips the region. And so, for more than a decade, states and the federal government have tried to wring more supply out of the Colorado and spread it further, in part by persuading the farmers and ranchers who use the vast majority of the river’s water and have the largest water rights to conserve it.

But in many ways it’s the vast body of often-antiquated law governing western water rights, officials acknowledge, that actively undermines conservation, making waste — or at least heavy use — entirely rational.

“Water is money,” said Eugene Backhaus, a state resource conservationist for the U.S. Department of Agriculture’s Natural Resources Conservation Service, which works to help ranchers use water more efficiently. “The way the current water law structure is, if they don’t use it for the assigned use, they could lose the water right.”

Adding to the problems, the states linked by reliance on the Colorado govern their water resources separately and have not standardized their water laws. While states have made incremental adjustments to those laws, they have not recast them to address the new needs of a region undergoing vast changes. Some rules force ranchers to dry up entire streams; others ignore the ecological value of maintaining a healthy river. The common element of all these laws is the blunt ethos of the West: Water exists mainly in order to get used up, even if that means deepening the problems of neighboring states.

Ketterhagen understands that the ranch he runs sits atop a system under enormous stress and that he’s wasting water in a region that desperately needs it. But he also understands Colorado water law — rights are precious, and sometimes more valuable even than the land to which they are attached.

Throughout the long, hot summer, Ketterhagen let water course through his fields, irrigating his pastures and vitalizing the gravelly soil beneath. Last spring, the water flowed over the grass’s roots, drowning them, and climbed past the first leaves of the sprouting plants until it stood calf-deep.

“She’s my gauge,” Ketterhagen said, pointing at Gilli, his black and white Aussie heeler mix, who bounded around the field. “When I see a little bit of spray kicking up behind her, it’s just right.”

The body of law governing how water is distributed in the West was shaped by the gold rush.

As people were lured to settle vast, uninhabited and arid parts of the country, they staked their claims to land and water only to face fierce competition upstream as rivers were diverted to sluice for treasure. Courts decreed that water would be saved for the first to use it. Since most property was far from streams and there was little rain, officials then gave settlers formal rights to take water out of rivers and move it across dry land where it could be used to mine minerals or turn rocky fields into farms.

As western territories became states, those states institutionalized the rules — sometimes in their state constitutions — first locking in water rights for those who were already there and then issuing more to those who requested them, on a first-come-first-served basis. For irrigation, shares were apportioned according to crude 19th-century notions of how much water was needed to get 40 acres of dry soil to produce a crop. In times of drought, those with the oldest, or most senior, rights to water would get it first; those with the newest rights would have to wait at the back of the line.

It wasn’t until the 1920s that the seven states whose territory was touched by the Colorado River and its tributaries began to compete for access to the source of that water. Herbert Hoover, then the U.S. Secretary of Commerce, led negotiations in which the states agreed on an estimate of the amount of water in the river. The rights to most of the flow were split between states in the upper and lower basins. Colorado, Wyoming, Utah and New Mexico got half, while Arizona, California and Nevada got the rest. This was, in part, to keep California — already the most populous and industrious of western states — from taking it all. Each state continued to govern the rights to water distributed within its borders.

But even in that first 1922 compact, more water was divvied up on paper than would actually run through the river. Officials, it turned out, had estimated the Colorado’s average flow after a period of unusually wet conditions, calculating that 18 million acre-feet flowed through the river each year, and dividing up some 15 million acre-feet, or 4.8 trillion gallons of water, between the states. Within two decades they began to understand their folly: During many years as little as 12 million acre-feet flowed, and under normal conditions the river would rarely yield close to the amount of water expected. And yet the states piled on more obligations, bringing the amount of water parceled out even higher. In 1944, for instance, Congress signed a treaty promising an additional 1.5 million acre-feet to Mexico, where the Colorado River naturally ends.

Today, 15 years into an epochal drought, 16.5 million acre-feet of water have been allocated, while the river, during the recent drought, has been flowing at a rate of around 12.4 million acre-feet each year.

Still, aside from a 2007 temporary pact to divide the pain of river shortages between them, officials in the seven states have never renegotiated the original river compact or fundamentally changed the foundations of water law that lead to overuse. The result is a set of codified principles designed for a different era and divorced from today’s environmental realities.

The term “water law” in the Colorado River basin has come to refer to a monstrous volume of federal statutes and agreements, court precedents and state laws and regulations that can differ from place to place and have changed incrementally over the years but are structured by the interstate agreements to divide the river. Most of those state laws share the basic principle that the first people to arrive in the West should hold the most senior rights to its water.

The notion of “first in time, first in right” has persisted even as the need for water has exploded in urban areas that sprang up long after most water rights were distributed and therefore rank lowest in priority.

Fly-fishing, rafting and mountain tourism contribute billions of dollars to Colorado’s economy, yet in most cases state law distributes rights to a majority of water in streams and tributaries to farmers and ranchers and incentivizes them to leave little, if any, for recreational use. Many small streams in the Rockies run dry by midsummer, often because ranchers don’t have a reason to let water pass them by.

“Ninety percent of water users thought water running downstream was wasted water,” said Cary Denison, the Gunnison basin project coordinator for Trout Unlimited, a sportsmen’s and river conservation group working with ranchers to get them to use less water.

Years of worsening water scarcity passed before those ranchers began to appreciate how their practices — and the laws guiding them — were contributing to the problem. “Only recently do we start to see articles in the paper about the drought, and we think, gosh, we have some effect on this,” Denison said.

Even when there is no more water to distribute, Colorado officials can certify place holders in an endless line, assuring that water will be overallocated forever and that someone will always use whatever the last person leaves untouched.

“The whole system is designed towards preserving the status quo,” said Jim Lochhead, the chief executive of the urban utility Denver Water, who formerly represented Colorado on interstate water negotiations. The most pragmatic approach, he thinks, is to build off existing water law while reforming its worst parts. But in a perfect world, he said, “I would abolish Colorado water rights law and start all over again with a clean slate.”

None of the antiquated parts of what across the entire basin is referred to loosely as “water law” play as much a role in stressing the water system — or seem as fixable — as the one known as “use it or lose it.”

Originally devised in part to keep speculators from hoarding water to build wealth and power, the intent of “use it” laws was to make sure the people who held rights to water exercised them. They could keep those rights indefinitely, passing them on through generations or selling them, attached to the land, at great profit, as long as they constantly put the water to what most Western water laws refer to as “beneficial use.”

Each Colorado River basin state has a variation of rules promising to confiscate water rights if water users don’t maximize their use. While some of the laws allow for state-approved conservation or other flexibility, legal experts say ranchers often understand the laws to be absolute. Colorado authorities keep a list of property owners whose water rights are primed for “abandonment,” meaning that the full extent of the rights haven’t been exercised, by intent and on average, over a 10-year period.

The provision leaves landowners feeling they have little choice but to take as much as they are allowed, and many do it year in and year out to preserve the value of their property. “I would say to my clients: ‘You have to protect yourself … by using the water that is appropriated,’” said John McClow, a prominent water rights attorney who represented the state on the Upper Colorado River Commission, the interstate water management coalition, and now serves on the Colorado Water Conservation Board. But maximizing their rights keeps the river under maximum strain.

It’s not just ranchers who feel they must use up water for fear of losing rights to it. Towns, counties and even states do more or less the same thing, not necessarily because they are bound by abandonment clauses like ranchers but because they harbor fears of losing their water as it flows out of state. There is a push for Colorado to maximize its use of all the water it can.

“The state of Colorado is supposed to double in size by 2050,” said Marc Catlin, who sits on the board of the Colorado River Water Conservation District and represents Montrose County, which has filed applications to snatch up additional conditional water rights for its own future growth. “And somebody has got to be thinking about the future if that’s the case.”

The effects of “use it or lose it” laws are so significant that policy experts warn that western states won’t be able to begin untangling larger issues of drought and conservation without dealing with it first. “It’s fundamental,” said Laura Ziemer, senior counsel for Trout Unlimited and a leading expert on water law.

Any reform would probably have to happen state by state. States are fiercely protective of their sovereign rights to govern their water resources, and the federal government has repeatedly pledged not to interfere. Challenging state leaders on that, said Pat Mulroy, the former head of Las Vegas’ water authority and Nevada’s former negotiator on the Colorado River, is a sure way to “see eyeballs start popping out and bones start showing up on the side of their backs.”

At the state level, suggestions that the “first-in-time” water rights policies might be modified triggers an equally radical reaction, conjuring fears of property seizure and a nearly religious opposition to change. Even the most ardent supporters of such changes — people like Lochhead of Denver Water — admit water laws are probably too sensitive to be reformed any time soon.

Still, overhauling “use it or lose it” clauses would protect property, could offer quick improvement for water supplies and has the support of many ranchers.

Recognizing that its groundwater aquifers were being rapidly depleted, Kansas passed legislation protecting farmers’ full water rights even if they choose to use less water in any given year. But efforts to pass a similar measure in Colorado have so far failed. Last year Colorado’s governor vetoed a bill that would have allowed ranchers to use less water without jeopardizing their long-term entitlements, and an effort to revive the issue earlier this year hit a dead end. Some ranchers — including Ketterhagen — wanted to see the water they didn’t need stay in the river, where it would support the state’s booming fishing and outdoor tourism economy. But others, including those with more junior water rights, didn’t want to give water to trout — or to lower basin states.

“Do we want to fix it in a way that sends more water to Arizona?” asked McClow, the water attorney. “We’re still parochial about that. If we save some water, I think we want to use it ourselves.”

Across the fields from the ranch managed by Ketterhagen lives Bill Trampe, a significant user of Colorado water and one of the most influential.

Like his father and grandfather, Trampe, 68, harvests alfalfa on what is now 6,000 acres of picturesque rolling hay crops and grassland 30 minutes outside the town of Crested Butte. His grandfather cleared stones and dug the miles of irrigation ditches that bring water to the ranch with his own hands.

Trampe sits on the boards of the Colorado River Water Conservation District and the state’s Interbasin Compact Committee. Many of the River District members at first supported Colorado’s attempt to fix the “use it or lose it” law last year. But when Trampe — who argued the law would embroil ranchers in expensive legal and engineering fights to defend their water rights — came out in opposition, momentum shifted against the bill, and the governor ultimately killed it.

Trampe, like many alfalfa ranchers, flood irrigates his pastures, and he says that while the water he dumps on his fields can seem excessive, it serves other invisible but essential purposes. He fears a law that encourages farmers to conserve water would have unintended consequences on a complex natural system.

Driving his combine tractor, his thick, calloused hands wrapped over the vinyl steering wheel, Trampe described his fields in the way that only someone who has spent his entire life on the land can. Because his rocky soil drains quickly, the extra water he applies seeps downward and keeps the underlying aquifer full, he says. What water isn’t sipped up by his own plants flows underground downhill to benefit his neighbors, and ultimately to provide a steady flow of water back into the river itself.

Before there was farming, Trampe says, there wasn’t much of a ground water supply in his part of the valley north of Gunnison. But today households there depend on water wells for bathing and drinking, and those wells tap into a water table that is kept artificially high by the overuse of irrigation water on the ranches. There is also the drain water: “return flows” that seep back into the river to be claimed again by “junior” water rights holders downstream.

Return flows are an essential component of Colorado water accounting, and ranchers like to say their water is recycled four or five times by the time it gets all the way down to the main stem of the river. Among Trampe’s concerns is that conservation would wind up cutting off return flows the next farmer counts on.

“Over a century, we’ve been irrigating this country, and we’ve established an ecology based on what we’ve been doing,” he said.

Trampe also sees conservation efforts as a sort of Trojan horse. He says that, squeezed between Denver to the east and all the big thirsty desert cities downstream, Colorado’s ranchers are under siege.

“The municipalities will come here and condemn us, or buy us out,” he said.

Indeed, western cities have become increasingly critical of the imbalance between rural and urban regions when it comes to rights to water. “There is a very small number of people that control a huge amount of water,” said Douglas Kenney, director of the Western Water Policy Program at the University of Colorado Law School in Boulder. “Is it truly equitable that water was allocated 100 years ago and now we are locked into that forever?”

Denver and other eastern Colorado cities already take 154 billion gallons of water across the Continental Divide from western Colorado each year. Schemes to build more tunnels to divert more water from rural western areas like Gunnison are a constant concern. And last July the utilities and groups that represent the lower river states’ biggest urban areas — including Las Vegas, Denver and Los Angeles — proposed a pilot program to find additional water supplies in the agriculturally rich parts of Colorado, in part by paying people like Trampe to fallow fields, be more water-efficient or perhaps lease or sell their water rights.

“The cities continue to grow and grow and grow … and they expect me — or us as an industry — to give up water,” Trampe said. “Why should I suffer for their sprawl?”

In 2012, it hardly snowed in Colorado. Even in the Colorado River’s uppermost reaches, streams narrowed to a desperate trickle in the early summer, and long before Gunnison’s ranchers could take their water, Ohio Creek and the other tributaries nearly ran dry. A strange thing happened as a result.

Walking through shoulder-high Garrison grass, Ketterhagen recounted the lessons of that summer: His fields did great, perhaps better than they have done since. He has come to think the grasses — a pasture mix of slender wheat, Garrison, clover and alfalfa — suffer with too much water. The dry year trained them to withstand the rigors of water shortages in the future. “If you are able to irrigate your crops with less water over time,” Ketterhagen said, holding his arms out and letting the silky plumes brush his palms, “I think you could create a more drought-resistant hay crop.”

There’s no quicker way to make a Colorado rancher bristle than to suggest that the water he applies to his meadows is wasted, but the science — and Ketterhagen’s observations — suggest many water users could get by with less.

According to the Natural Resources Conservation Service’s Backhaus, an alfalfa plant in particular, set in saturated soil, will grow weak roots only half as deep as normal. The saturation can bring more disease and insects and grow a plant deficient in iron. Alfalfa is the thirstiest crop grown in western Colorado, consuming as much as 3 acre-feet of water per acre of crop each year. But it’s not uncommon for local ranchers to deliver 4 to 6 acre-feet of water, taking twice as much water from the river as their crop needs. If it doesn’t drain, that much water can suffocate the plants and they will be overtaken by sedges and other species.

“Saturated soil actually doesn’t have oxygen in it, and so you will start seeing more of that wetland type plant growing in it,” Backhaus said. “By continually irrigating — letting the water go over a field and never stopping it — it could turn into an artificial wetland.”

Even where crops aren’t overwatered, water is lost just by transporting it from the river to the field. Copious amounts evaporate out of the ditches that line the hillsides and seep out the bottom into the loamy soil, well before the water even gets to ranchers’ fields. Ranchers know this; they open the gates long before they need the water, allowing extra time for the soil to get saturated enough to hold water.

Along the banks, the roots of weedy tamarisk shrubs guzzle even more water, and sedges grow in depressions — a sign of moisture pooling where it isn’t needed. As Trout Unlimited’s Denison points out, flood irrigation is just 35 percent efficient, meaning nearly two-thirds of the water taken out of the river is lost, and never gets used by the grasses it is meant to nourish. The extra water is presumed to ultimately return to the river — and is counted that way when the state tallies up its usage — but Denison and others say only some of it actually does.

Denison sees opportunity in the margins. Rather than a black-or-white struggle between agriculture and cities, a compromise could send more water downriver while keeping the farms in business. But finding it requires rethinking water entitlements, and more flexibility than existing laws allow. California has been grappling with this realization as its most senior water rights holders have begun to relinquish part of their share. “There is plenty of water to meet current needs, but we have to define what needs are, versus what a ‘right’ is,” Denison said.

The Natural Resources Conservation Service offers financial incentives to help ranchers upgrade equipment and adopt new, more efficient irrigation technologies. A pivot irrigation system — in which a long sprinkler pipe is set on wheels and rotates from a fixed point, leaving lush green crop circles — can potentially cut water use in half. Remote-controlled water ditch gates allow ranchers to shut off flows they otherwise leave running for months at a time because they are too far up in the mountains to visit. Drip irrigation for vegetable crops, in which small amounts of water are emitted right at a plant’s roots, is estimated to be as much as 95 percent efficient.

Standing at the top of a meadow full of Timothy and wheat grasses, Ketterhagen points to a 12-inch PVC pipe running beside an empty 2-foot-deep dirt ditch that it replaced. He worked with advisers from the NRCS to design the pipe system and install it on part of the ranch. The pipes don’t lose water en route to the field and let Ketterhagen distribute water more evenly. Within a week, he says, his water use on that section of the ranch seemed to drop by about half.

Federal officials believe the subsidy program could successfully prod ranchers to put hundreds of billions of gallons of water back into the river and help relieve the shortages plaguing states downstream. “If every producer did that … there would be measurable gains,” said the NRCS’s Backhaus. “If 50 percent of them did it and they got a 10 percent gain, that would still be measurable.”

And yet ranchers have been slow to adopt changes. Their reasoning varies from the practical — Gunnison-area ranches often grow only one cutting of alfalfa a season, putting the $90,000 cost of some pivot irrigation systems out of reach — to the cynically ideological. “If you save it you lose it. You don’t get paid for it. You just give it up,” said Patrick O’Toole, president of the Family Farm Alliance, a national farmer advocacy group that advises Washington policymakers, repeating complaints he says he hears from some of his members. “So why would you give up water for use you don’t even believe in, for nothing?”

The risk to long-term water rights figures prominently in ranchers’ thinking. If Ketterhagen piped every ditch on the ranch he runs, the pipes might not even carry enough water for the owners to be able to take their full allotment out of Ohio Creek. The Colorado authorities could confiscate their water rights. Ketterhagen’s employers would lose much of the value of their land, and Ketterhagen expects he’d be out of a job. Federal officials say similar concerns weigh on other ranchers, and that “use it or lose it” statutes create a strong headwind for the government’s conservation program, prompting ranchers to worry about becoming too efficient for their own good.

“It kind of runs crosswise with the goal of our program,” said John Scott, a former district conservationist for the NRCS in Gunnison.

Many of the same ranchers who insist they need all of their water also say they could use less if their rights were protected and they benefitted from the savings. “Why shouldn’t we have a say in how those savings are used?” asked Ken Spann, one of western Colorado’s significant water users, who farms thousands of acres between Crested Butte and the town of Delta downstream. “Do I have a moral and ethical obligation as a citizen of Colorado to ensure that they can continue to expand the metropolitan area toward the Kansas line? I don’t think I do.”

Spann would support a change in the law if it allowed him to retrieve the water he saved one year and use it the next. For now, he says, he has no good reason to use less water.

“People behave rationally,” said the University of Colorado’s Kenney. “The incentives are structured in a way that they are encouraged to act in a way that isn’t in society’s best interest.”

There is a consensus that this status quo has got to change. There is going to be less water and increasing pressure to use it efficiently.

“It’s like I’ve got a devil and an angel on my shoulder,” Ketterhagen said. He wants to see a healthy river and applauds an effort last spring to send a surge of water to the river’s end to restore its delta. “On the one hand the Colorado River flowed all the way into the Sea of Cortez this year, it brings a tear to my eye.”

“On the other, we give them our water and what do we get in return?”

Naveena Sadasivam contributed to this story.