On Drought

I finally got around to reading the Pielke Sr. et al. paper on drought in Colorado in 2002 (paper here and Roger blogged it here).

The data’s Colorado-specific, but the New Mexico data doesn’t look that much different, and the message here is pretty much the same. What we viewed as an “exceptionally severe drought,” as measured against historical and paleo records, really wasn’t. It’s our water needs that have changed as population has exploded here in the intermountain west:

The sobering conclusion is that Colorado is more vulnerable to drought today than under similar precipitation deficits in the past.

I don’t know that anyone’s done the same sort of analysis for New Mexico, but a simplistic look at the data shows that the exact same situation is the case here. Using the Western Regional Climate Center’s climate division data set, you find that the 2001-02 water year in New Mexico was the third driest in the 110 year record in the state’s northern mountains – key for snowpack and also where we saw huge piñon dieoff. Here in the Rio Grande Valley, where the bulk of the state’s residents live, 2001-02 just barely made it into the top one third driest years.

Given the importance of multi-year droughts here, it’s not unreasonable to look beyond 2002. By that measure, the three years ending in 2002 were the driest such stretch since the 1950s, but they comprise just one of six droughts that were similar or worse since the late 1800s. And the 1950s were way worse. As Steve Bloom pointed out in the comments on Roger’s blog, the paleo record suggests there’s much worse out there waiting to bite us.

It’s also worth pointing out that the period from the mid 1970s to the late 1990s was unusually wet in New Mexico. Between 1970 and 2000, New Mexico’s population grew 80 percent. It’s worth remembering Kelly Redmond’s simple but useful definition of drought: “Insufficient water to meet needs.”