La Niña, an event characterized by below-average temperatures and cooling of the Pacific Ocean surface, brought an unusually warm and dry winter to the Southwest last year and is likely to worsen drought in New Mexico for a second consecutive year.
Cold water on the equator influences the subtropical jet streams, which are air currents in the atmosphere, and shifts colder weather conditions northward, according to University of New Mexico Professor Emeritus of Earth and Planetary Sciences David Gutzler. The effect is warm, dry air rising in the Southwest.
Though La Niña is happening, it’s not a cemented guarantee that this winter will be dryer, but it does tilt the odds in that direction, according to John Fleck, professor and director of the UNM Water Resources Program.
“(This year) we’re looking at the prediction of warmer-than-average temperatures and lower-than-average precipitation in the next several months,” said Andrew Mangham, the Senior Service Hydrologist for the National Weather Service of Albuquerque.
While there aren’t necessarily hard and fast metrics to quantify when New Mexico will start to endure La Niña’s effects, scientists will know the gravity of a La Niña season beginning in January or February, when the winter snowpack is measured, according to Mangham.
“(National Oceanic and Atmospheric Administration) models are indicating that the La Niña that’s developing … is likely to persist and, in fact, intensify through the winter,” Gutzler said. “Once we get into the winter, then it starts to affect North America.”
Mangham said major tributaries of the Colorado River, such as the San Juan River and Gila River, will be affected by La Niña.
“(Snowpack) is one of the things we look at here in New Mexico, because that’s what drives the water supply,” Mangham said. “We’ll start looking at precipitation amounts, accumulated snow (and) snowpack development up in the mountains.”
Due to New Mexico’s existing drought, a second dry winter would prolong the drought another water year, which is an annual measurement of precipitation, according to Gutzler.
“A lot of the climate here in the Southwest hangs on winter precipitation,” Gutzler said. “For the major rivers like the Rio Grande, Pecos and San Jaun, they’re generally snow-fed, so if the snowpack is bad, that has effects that last through 2022.”
The impacts of already dry winters can be compounded by La Niña events due to the lack of precipitation, Mangham said.
“One of the things that’s causing some of our surface water issues is that the ground is so dry due to the prolonged drought that a lot of water that’s melting from the snowpack goes into the soil (instead of the reservoir),” Mangham said. “It can take years or decades, even, for that to recharge an aquifer.”
Though it’s still in prediction stages, Mangham said he expects that New Mexico will see a continued reliance on groundwater next year to make up for lacking reservoirs.
“In New Mexico, we enter the winter with pretty much all of our storage drained; we have no cushion left,” Fleck said. “It would potentially be a second very dry year for water users to depend on river flows … from the headwaters of northern New Mexico acequia communities down through the Rio Grande Valley.”
As the drought worsens, there’s a real potential for more stringent water restrictions in the state, which could affect livestock and crop yields, Mangham said.
Mangham emphasized that there’s a possibility that New Mexico could still see some snow in the mountains, which could alleviate the dryness.
“The bottom line here is that … the weather pattern we’re expecting does not look like good news for the drought situation,” Mangham said.
Fleck said La Niña impacts “tend to be more pronounced further south,” and that pecan and chile farmers in southern New Mexico will experience the ramifications of a dry winter through insufficient surface water availability.
Rebecca Hobart is a beat reporter at the Daily Lobo. She can be contacted at email@example.com or on Twitter @rjhobart