The West’s water security is under unprecedented strain, and the looming arrival of the super-El Niño is being viewed as a significant, yet insufficient, factor. The two largest reservoirs in the United States, Lakes Mead and Powell, provide critical water supplies for states along the lower part of the river; both have hit multiple record low points this month. Enter El Niño. This weather phenomenon, predicted to be the strongest in recorded history, is expected to bring increased rainfall and snowfall to the southwestern United States this winter and spring. However, experts caution that this precipitation may not be enough to mitigate the slow-building disaster on the Colorado River. Even a best-case scenario this winter, involving a healthy snowpack in the region helping to temporarily replenish the river, would be no match for the longer-term problems plaguing it.
The Colorado River is primarily fed by snowmelt from four states in the river’s Upper Basin (Colorado, Utah, New Mexico, and Wyoming), which then supplies the Lower Basin states (California, Arizona, and Nevada). Lakes Powell and Mead are crucial reservoirs that bring water to those lower states. A winter of record-breaking warm temperatures across the West—made much more likely by climate change—and some of the lowest snowpack on record in mountain ranges in multiple states has led to an incredibly dry season for the Colorado. On Thursday, Lake Powell was sitting at 3,519.4 feet, while Lake Mead was at 1,039.6 feet, their lowest levels on record. Both reservoirs will hit ‘deadpool’ at certain levels (3,370 feet for Lake Powell, and 895 feet for Lake Mead), meaning that water can no longer flow out of the reservoirs downstream. (Hydropower from dams on both reservoirs will be affected, or go offline entirely, even earlier.)
In a stroke of uniquely terrible timing, the river, whose water has for decades been over-allocated to thirsty industries like agriculture, is also facing a political crisis. A century-old compact dictating water rights from the river runs out at the end of this year, and states have missed several deadlines to figure out who gets what in the future, requiring the federal government to step in. Combined with the dismal water levels at Lakes Powell and Mead, it’s a terrifying situation for experts who have been watching the slow-motion crisis on the river suddenly accelerate. “People have talked about the Colorado River crisis for decades—we’re now in it,” says John Berggren, a policy manager at environmental nonprofit Western Resource Advocates. “Everyone you talk to is like, ‘Shit, man. This is the year.’ We’re really going to see: Can we get through it?”
A wet and snowy winter this year could help to temporarily stave off disaster as the states and the federal government scramble to come to a solution about the river’s future. And it’s true that El Niño should bring some relief to parts of the region that rely on the river. Berkeley Earth climate scientist Zeke Hausfather says that one of the most ‘reliable’ El Niño signals is wet weather in specific areas of the country, including some states that take water from the Colorado.
“A strong El Niño does load the dice toward a wet winter across the southern US, from Southern California through Arizona and New Mexico to the Gulf Coast,” he says.
Whether or not the crucial Upper Basin states, whose snowmelt feeds into the river and replenishes Lake Powell and Lake Mead, will get snowfall is another question entirely. Hausfather points out that during the last ‘very strong’ El Niño, in the winter of 2015-16, the river’s Upper Basin experienced a ‘normal’ amount of snowfall. “Peer-reviewed correlations between El Niño and Upper Basin snowpack or streamflow are modest at best,” he says.
This year’s El Niño is shaping up to be the strongest on record. A normal El Niño and a ‘ridiculously strong El Niño’ are ‘are almost two completely distinct things,’ says Daniel Swain, a climate scientist at the University of California Agriculture and Natural Resources. With how strong this El Niño is shaping up to be, Swain says, there’s a chance that some of the Upper Basin states could see some of that precipitation. But all experts say that the area most likely to be impacted is the Lower Basin states—which doesn’t do much to replenish Lake Powell and Lake Mead and help the river’s overall water supply.
Thanks to climate change, many states in the West have seen increasingly warmer winters, making snow droughts even more common. While Swain doesn’t think the West will see as warm a winter as last year, climate change has changed the baseline conditions of what constitutes a “normal” winter. That affects the kind of wetter weather that El Niño may bring. Precipitation can be ‘intercepted by drying soil, or re-evaporated directly into a thirstier atmosphere, or [fall] as rain rather than snow,’ says Swain. “That won’t have the same effect as a good snow year in 1980 or 1990.” “Even one big year is not going to save us,” says Beggren. “It might be a sigh of relief, but we’ll be right back in it.” ”
Watch Related Video
Source: Wired Science
