As Colorado snowpack suffers, La Niña could persist into summer
According to the latest forecast from the Climate Prediction Center, issued yesterday, the La Niña conditions that have contributed to the continuing drought in Texas and other regions are likely to persist through at least the Northern Hemisphere winter. And one ensemble modeling forecast from the CPC predicts that the abnormally cool sea surface temperatures in the Pacific Ocean characteristic of La Niña could continue at least through summer.
La Niña favors weather patterns that tend to bring drier than normal conditions across a large swath of the southern United States (as the map on the right in the graphic above shows). And that’s more bad news for Texas and New Mexico.
In central Texas, record-setting heat and drought in 2011 contributed to outbreaks of severe wildfire, and reduced flows into reservoirs that supply water to millions of city dwellers and farmers. For example, from January through November of last year, water flows into the Highland Lakes in central Texas — including reservoirs that supply the state capitol of Austin — have been less than 10 percent of average.
As for New Mexico, John Fleck of the Albuquerque Journal summarized 2011′s grim events in a retrospective article published on New Years Eve:
The new year will dawn with a calm that belies the wild weather marking 2011 in New Mexico.
From a deep freeze unprecedented in nearly four decades to a drought unprecedented in the past century to a similarly unprecedented fire season, 2011 was a year for the record books.
At its worst, 2011 left 79 percent of New Mexico in extreme drought or worse.
But it was really the long warm period, the brief extreme cold spell and the dryness that told the year’s weather story.
At the start of 2012, there is one bright spot: In a story yesterday, John reported that the snowpack in New Mexico “is looking surprisingly healthy for the first week of January in a La Niña year.”
Unfortunately, the same can’t be said of the Colorado River Basin. As John pointed out in a Tweet yesterday: “New Year starting with 62% of average snowpack on the #ColoradoRiver above Lake Powell http://t.co/Hh3Jrzzp #westwater.” Here’s the graph that tells the tale:
The waterways of the basin drain nearly 246,000 square miles of territory. They also serve nearly 30 million people in seven states and Mexico, including residents of Los Angeles, Phoenix, Tucson, Las Vegas, Denver, and Albuquerque, and irrigate more than three million acres of crops and pasture.
A satellite image of much of the Upper Colorado River Basin, captured by the MODIS instrument on NASA’s Terra Satellite on January 1st. (You can find an interactive version of the image here.) The mountains are snowy. There’s just not enough of the white stuff.
Over the long term, the use of Colorado River Basin water now exceeds supply. (I wrote about that situation in a story for Climate Central last year.) What has kept farm fields wet and water taps running? The reservoirs along the Colorado – particularly Lake Powell and Lake Mead. Higher than average runoff in the basin last spring helped replenish some of the water that had been drained out of those giant hydrological savings banks by extended drought. But one year is not a trend. So if the diminished snowpack at the start of 2012 is any indication of where we’ll be come spring, expect more stories about water woes.
As the precipitation forecast map at the top of this post shows, some parts of Colorado are expected to be wetter and others drier than average, thanks to La Niña. But squint at that map and you’ll see that the Colorado River threads the white space between those green (wetter) and brown (drier) forecasts. The basin could go either way.