Another water-short year in the Southwest is taking its toll
On April 14, a Sunday, the Colorado ski resort Vail Mountain celebrated closing day in the invariable way: Skiers and boarders sported neon onesies and mullet wigs. The less modest squeezed into denim short shorts to flaunt calves and quads sculpted over a winter on the slopes. Alcohol was overconsumed and confiscated in lift lines. But even without it, the mood was buoyant: It was, unusually, a 13-inch powder day. By Wednesday, 24 more inches had fallen. Skier spirits were still soaring the following Sunday when Vail hosted Closing Day, The Sequel. Pleading for a third closing day via Facebook, one powder hound goaded: "I dare you to close more times than Brett Favre has retired."
Colorado snowpacks -- which supply the Colorado River, a crucial water source for millions of Westerners -- began April at 72 percent of their average heft. Thanks to storms and frigid temperatures, instead of starting to melt as they typically do, north and central Colorado snowpacks ballooned last month. In late April, Old Man Winter was forcing Major League Baseball cancellations in relatively temperate Denver. Boulder set a record with more than 4 feet of snow that month. By May 1, statewide snowpack weighed in at 83 percent of average.
In the end, though, the spring storms were momentary distractions from the Southwest's real weather story: The region's major river basins, the Colorado and the Rio Grande, are still mired in a decade-plus-long drought. It's often said that persistent drought is the "new normal" here thanks to global warming, but that's something of a misnomer. Using tree rings, scientists have found that the region experienced droughts lasting decades, and even centuries, long before humans began meddling with the climate. The aridity we've experienced of late isn't any more extreme than it was then. But the heat is, and it bears a human fingerprint. The combination leads scientists to call it a "global-change-type drought," meaning more of the same can be expected in the Southwest as extreme heat exacerbates the region's characteristic dry spells.
Precipitation in the Rio Grande Basin is expected to decline by more than 2 percent at mid-century. It's highly uncertain how climate change will impact the moisture that falls on the upper Colorado, if much at all. But dust-on-snow events have already caused snowmelt to happen earlier in the year, a trend that reduces overall runoff by about 5 percent as more water is evaporated into the atmosphere from plants and soils. That's a significant amount for overstretched water supplies, and warmer temperatures are likely to intensify the effect. Troublingly, at the same time, water demand is on an upward trajectory.
This spring, the effects of hot, dry year upon hot, dry year are already beginning to make themselves painfully plain. That's especially true in New Mexico. Seventy-seven percent of the state is suffering "extreme" drought, which is only a little better than "exceptional" drought -- as bad as it gets, according to U.S. Department of Agriculture. A year ago, most of the state was in drought of the "moderate" variety. Even so, more than 30 miles of the Pecos River, in southeastern New Mexico, went dry last summer. This year, Carlsbad farmers are pressing the state to shut off Roswell farmers' groundwater wells, which they say are illegally draining the Pecos of water that belongs to them.
Drought has a way of bringing simmering conflict to full boil, and it did so concurrently on the lower Rio Grande. "The river here looks a lot like the Sahara Desert," says Phil King, water engineer for south-central New Mexico's Elephant Butte Irrigation District, which wets the chile and onion fields and pecan orchards around Las Cruces. Though Rio Grande Basin snowpacks were 67 percent of average in early April, runoff into Elephant Butte Reservoir through July was conservatively forecast at a pitiful 5 percent of normal, and after a decade of drought, the reservoir sits 90 percent empty. The "river" below it is a sand channel and will remain that way until June 1 when releases begin, and dry up again in early July when they end. Farmers are surviving on groundwater, but it's a safety net of diminishing returns. Wells are beginning to go dry or produce brackish water, and irrigators downstream in Texas have asked the Supreme Court to shut them off for the same reason Carlsbad wants Roswell's pumps idled. The system is dangerously near a breaking point.
"It's the most critically short year we've ever had in the history of the Rio Grande Project," a series of dams and reservoirs in New Mexico and Texas, King laments. "Each successive year of short water gets worse and worse."
That principle holds true on the Colorado River, though things aren't nearly so dire. Since 2000, demand for water has outpaced supply. Reservoir storage has made up the difference, ensuring the states below Lake Mead -- Arizona, Nevada and California -- get their full annual supplies. (Ironically, upstream of Lake Mead and Lake Powell, the system's largest reservoirs, where most of the water supply originates but storage is less formidable, water users have experienced shortages.) But the cushion the wet '80s and '90s provided is thinning. Lake Powell, the basin's second largest reservoir, was 85 percent full in 2000. Today, it's about 45 percent full. And this year, runoff in most of the Upper Basin is forecast lower than you might expect given the late boost to snowpacks because after a dry year -- in 2012, Upper Colorado snowpacks topped out below 70 percent of normal -- the landscape has cottonmouth. Parched soils take a cut of the snowmelt that would otherwise fill rivers. After snowmelt, the water line of Lake Powell will likely sit below even last year's modest peak.
"The more severe the drying with climate change, the more likely we will see shortages and perhaps empty reservoirs despite our best efforts," said Ken Nowak in 2009, upon the release of a study he co-authored on whether smart management could mitigate the risk of water shortages on the Colorado River. It found that the risk of the Colorado's big reservoirs emptying in the next 15 years or so was slight. Still, Nowak's cautionary note remains as true today as it was then: "The important thing is not to get lulled into a sense of security with the near-term resiliency of the Colorado River Basin water supply. If we do, we're in for a rude awakening."