Tuesday, October 19, 2010
Fears of Dry Winter Intensify With La Niña
By John Fleck
Journal Staff Writer
David Gensler seemed unusually glum when I dropped by his office a couple of weeks ago.
October is usually a quiet time of year for Gensler, who manages water for the middle Rio Grande's largest irrigation agency. The weather's cooling, leaves are turning, crops are slowing down, and Gensler and his team are getting ready to shut down the Middle Rio Grande Conservancy District's irrigation system for the winter.
In terms of managing the district's water supplies, there's not much to do over the winter except wait to see how much snow falls in the mountains of northern New Mexico and southern Colorado.
But this year, it sounds like Gensler also will spend some time worrying.
For starters, it's been warm. The early October day we met at his office, the temperature was 6 degrees above average, consistent with our weather since the start of September.
Warm weather means more water consumption right now.
Gensler's office is about 500 yards from the Rio Grande, where the trees are sucking water out of the river and nearby groundwater system like it's still late summer rather than early fall.
The warm weather also means some valley farmers will be able to get in a fifth alfalfa cutting, which means more irrigation.
Meanwhile upstream, Gensler's reservoir storage — water he's trying to hang onto for next year's farm season like a tight-fisted corporate accountant — is low. It's not awful, and in most years the amount he has in El Vado reservoir on the Rio Chama would leave him a comfortable margin for next year. It snows in the winter, the snow melts, and Gensler's reservoir storage fills up in the spring.
But climate scientists are sounding an increasingly loud alarm about the risk of a dry winter — possibly very dry.
This year's forecast reflects the convergence of powerful forces.
You've probably heard part of this before — the rapid strengthening of "La Niña," a band of unusually cool water across the equatorial Pacific. The area of the ocean it covers is vast, and it has a tendency to push the North American winter storm track to our north. We still get storms in a La Niña year, but on average we get fewer.
Ed Polasko, at the National Weather Service's Albuquerque office, has gone back through the records to make sense of what we're seeing. He found that you have to go all the way back to 1955 to find a La Niña that came on this strong, this fast.
In strong La Niña years, like this one, New Mexico averages just 67 percent of its normal winter precipitation, according to Polasko.
That has Gensler worried there might not be enough snowpack for him to store much additional water for next year's irrigation season.
But more than La Niña is at work this year, according to Glen MacDonald, a climate researcher at the University of California Los Angeles.
Beyond La Niña, in the equatorial Pacific, researchers like MacDonald have been watching two other large-scale ocean patterns that also seen to have their own influences on North American droughts.
One is a long-term, persistent pattern of warmer water in the north Pacific. The second involves vast stretches of warm water in the north Atlantic. This year, they all seem to be lined up alongside La Niña, ganging up in a worst case scenario for drought in the Southwest, MacDonald told me.
When all three are in sync, according to MacDonald, "the propensity for drought indeed extends east from California right across your region to Texas."
The most famous case of oceans in sync like this was during the heart of the drought of the 1950s — New Mexico's worst in the last century.
That is an inauspicious way to start a new "water year," the water managers' calendar that begins Oct. 1 as irrigation is winding down and people prepare for the snow season.
The year just completed was wet enough for all the farmers served by Gensler's agency to get their full allotments. And overall, the state's northern reservoirs are in reasonably good shape going into water year 2011.
Abiquiu and El Vado, the two Chama river reservoirs that hold water for use in the middle Rio Grande Valley, are currently at above-average levels.
Elsewhere in New Mexico, things are less encouraging. Statewide, reservoir storage on Oct. 1 was just 71 percent of normal. Flow into Elephant Butte, the Rio Grande's largest reservoir, was just 58 percent of normal during the 2010 runoff season, and the big reservoir currently sits at just 30 percent of average for this time of year.
Gensler is walking a fine line here. The forecasts are more a suggestion of the odds than a firm prediction, and he doesn't want to unduly alarm valley farmers. But the reality of current water in storage and grim forecast is worth noting.
"I haven't been in that situation for a number of years," Gensler said.
UpFront is a daily news and opinion column. You can reach John Fleck at 823-3916 or firstname.lastname@example.org.