FABENS, Texas >> On maps, the mighty Rio Grande meanders 1,900 miles, from southern Colorado’s San Juan Mountains to the Gulf of Mexico. But on the ground, farms and cities drink all but a trickle before it reaches the canal that irrigates Bobby Skov’s farm outside El Paso, Texas, hundreds of miles from the gulf.

Now, shriveled by the historic drought that has consumed California and most of the American Southwest, that trickle has become a moist breath.

“It’s been progressively worse” since the early 2000s, Skov said during a pickup-truck tour of his spread last week, but he said his farm would muddle through – if the trend did not continue. “The jury’s out on that,” he said.

Drought’s grip on California grabs all the headlines. But from Texas to Arizona to Colorado, the entire West is under siege by changing weather patterns that have shrunk snowpacks, raised temperatures, spurred evaporation and reduced reservoirs to record lows.

In a region that has replumbed entire river systems to build cities and farms where they would not otherwise flourish, the drought is a historic challenge and perhaps an enduring one. Many scientists say this is the harbinger of the permanently drier and hotter West that global warming will deliver later this century. If so, the water-rationing order issued this month by Gov. Jerry Brown of California could be merely a sign of things to come.

Arizona, a party to a Colorado River water-sharing compact among seven states, already is bracing for a first-ever reduction in its allotment within a couple of years should the river’s main reservoir, Lake Mead, continue falling beneath its current historic low.

Since coming to office two years ago, U.S. Interior Secretary Sally Jewell has elevated water management in the West to an agency priority. “The challenge is systemic and persistent across the West,” Michael Connor, the deputy secretary of the interior, said in an interview. “We need better infrastructure, better operation arrangements, better ways to share water and move water.”

The perils of drought are on ample display along the Rio Grande, where a rising thirst has tested farmers, fueled environmental battles over vanishing fish and pushed a water-rights dispute between Texas and New Mexico to the U.S. Supreme Court.

But you can also see glimmers of hope. Albuquerque, the biggest New Mexico city along the Rio Grande, has cut its water consumption by a quarter in 20 years even as its population has grown by a third. Irrigation districts and farmers – which consume perhaps seven of every 10 gallons of river water – are turning to technology and ingenuity to make use of every drop of water given them.

John Fleck, a journalist and scholar at the University of New Mexico Water Resources Program who is finishing a book on the Colorado River, said no one should dismiss the gravity of the West’s plight. But neither is it necessarily ruination.

“This whole running-out-of-water thing isn’t really doom,” he said. “When water gets short, farmers get very clever.”

An untamed, flash-flooding home to sturgeon and eels a century ago, much of the Rio Grande today is little more than a magnificently engineered pipe – diverted, straightened, dammed, bled by canals, linked by tunnel to the Colorado River basin in the north, surrendering its last trickle in the south to a ditch that supplies farmers near El Paso. Only miles later do Mexican tributaries renew its journey to the gulf. Its raison d’etre is to sustain the booming society along its banks.

Skov, 44, is at the very end of that pipe. The canal that supplies his farm intercepts the Rio Grande near downtown El Paso and flows through the city zoo. From parts of his 1,500 acres, where he tends pecan trees and grows onions and alfalfa, he jokes, he could hit a nine-iron across the barren Rio Grande channel into Mexico.

In a perfect world, his crops could consume up to four feet of water in a growing season, and in flush times, 15 years ago, the canal gave him most of that. “We’d double-crop – do onions and come back with corn after that,” he said. “We used to grow a lot of chiles, a lot of jalapeqos. When water was abundant you could do a variety of things.”

That is a pleasant memory. Today Skov fallows a fifth of his fields, and canal water that once flowed from March to October arrives in June and vanishes as early as August. He makes up the deficit with two inches of treated water from the city sewage plant and a deluge of salty groundwater, brought up by once-abandoned wells that his grandfather dug, and that he has brought back to life.

The brackish water poisons the plants even as it saves them, cutting his yield by as much as a fifth. “It hurts germination, plant vigor, growth, root vigor, water absorption – everything negative that can happen to a plant,” he said.

Then again, the alternative is worse.

Across the West, the water shortages plaguing farmers and townspeople alike share many of the same causes. Like the Sacramento River in California and the Colorado River in the Rockies, the Rio Grande gets much of its flow from melting mountain snow, and snowpacks are getting smaller and melting faster.

Rising temperatures are the reason. The U.S. Bureau of Reclamation, which manages much water in the West, reported in 2013 that average temperatures in the upper Rio Grande, in Colorado and New Mexico, rose almost 2.8 degrees during the 40 years ending in 2011 – and could rise an additional four to six degrees by 2100.

The 40-year increase, twice the global average, was beyond anything seen in the last 11,300 years. Future warming “has the potential to cause significant environmental harm and change the region’s hydrology,” the bureau’s analysis stated.

A warming climate turns some snow into rain and increases the evaporation and melting rate of what snow remains. And as drought worsens, dust and soot from parched soil and burning forests coat the snow and absorb sunlight, turbocharging the melting.

This month, federal forecasters pegged the runoff from mountain snowpack feeding the Rio Grande’s northern stretches at roughly half the average logged in the final two decades of the 20th century.

“The last four or five years running, we’ve had a weak snowpack, early melting and really dry spring weather,” said Fleck, the journalist and scholar. “The spring runoff usually peaks in early May. I think it may have peaked in March this year.”

It is likely to get worse. While acknowledging that climate forecasts are inherently uncertain, the reclamation bureau’s 2013 analysis concluded that the Rio Grande could lose roughly a third of its water by this century’s end.

Experts say water users should stop fighting and start preparing together for a much drier future. “Individually, the American culture of using as much water as you want has got to stop,” said Pat Mulroy, a veteran Nevada water regulator who is a senior fellow at the Brookings Institution.

On that point, at least, Texans and New Mexicans seem to agree. In many places along the Rio Grande, governments and farmers are both cutting their use of water and finding innovative ways to produce more of it.

For example, El Paso’s irrigation district and water authority are building their own 400-acre rainwater basin, and in 2017, the authority plans to build an $82 million plant to recycle sewage into 10 million gallons a day of drinkable water.

El Paso now uses less water per person – about 130 gallons a day – than any city in Texas. Per-person use in Albuquerque, New Mexico, which won an international award in 2006 for water conservation, reached a record low last year.

John Stomp, the chief operating officer at the Albuquerque Bernalillo County Water Utility Authority, said he believed that with further conservation efforts and more cooperation among water users, the Rio Grande’s users could withstand even a permanently more arid climate.

But “it won’t be easy,” he added. “Nothing about water is easy.”

© 2015 The New York Times Company