Warm storms are nice, but they're no salvation
Meteorologists have a vivid term for the sort of storm we had during the first weekend of February: an atmospheric river. The rain certainly brought Reno a welcome drink, but probably hasn’t made much difference as far as the current drought is concerned.
“These are the kind of events our area really depends on to build up our water supply,” said Jeff Anderson, a hydrologist with the USDA’s Natural Resources Conservation Service. “It’s just unfortunate that this one’s a little too warm. The precipitation will certainly help, but it’s probably not going to boost our snowpack numbers too much.”
Both water supply and snow “look pretty dire right now,” he said before the storm rolled in, citing a January which by many accounts was record-breaking.
Since the early 1980s, 24 NRCS data stations have measured snowpack in the Sierra. Last month, 20 of those were the driest they’ve ever been, and the rest showed the second-driest numbers ever recorded. Meanwhile, a measuring station near Camp Richardson got zero snow in January for the very first time. This particular snow course has been around since 1951, mind you, and at the start of 1952 it saw more than 90 inches.
“The other part of the story is that this is now the fourth dry winter, and so the reservoir storage that was good at the end of the 2011 winter has been more or less depleted,” Anderson said. “Tahoe is evaporating water below its rim, so there’s not even the ability to get water out, and the other reservoirs in our region are also very low. … It’s not looking good for the farmers, is what I would say, unless things turn around.”
To reach normal snowpack levels by April 1, “we’d have to do better than about 90 percent of the historical record,” he said. “Though chances are, we’re not going to have January, February and March all be dry months.”
So what gives?
“In terms of whether it’s climate change or it’s not climate change, seasonal snowpack’s not really a good gauge,” Anderson said. “There’s so much variation from year to year. If you look at 2011, that was one of the biggest years on record. So I would just say that here’s a lot of variability in our climate in the Sierras.”
Valentine’s Day and the subsequent week may bring more rain, said Chris Smallcomb with the National Weather Service, “so hopefully that pans out.”
Droughts haven’t been unusual in recent decades. But the nature of our current drought—the fact that it’s so warm—has made this one especially problematic.
“When you have warm temperatures, it melts the snow faster, and it evaporates water out of plants faster, so those two things make the drought more severe,” Smallcomb said. “That’s why this drought is nastier than other ones recently. We’re seeing these storms come in, and they’re good, but what we really need are colder storms that have more snow with them.”