Is Lake Powell really shrinking?

 

The West is heating and drying up so much that the whole place could burst into flames at any second. At least, that’s the way it seems, reading the news these days. Every day it’s another item about the catastrophic, unprecedented drought and the “new normal” of months of consecutive 90+ degree highs in places like Denver and Boise. Worse, even the tubers are high-centering on rocks in my hometown river, the Animas, which has reached its fourth lowest level (after 2002, 1934 and 1977) in the past century. 

So, with the dismal water year of 2011-2012 (Oct. 1 - Sept. 30) coming to an end, I figured I’d get some perspective on the situation by looking at one of my favorite and reviled barometers of the state of the climate: Lake Powell.



Since it finished its long, slow fill-up in the early 1970s or thereabouts, Lake Powell’s surface elevation has reflected the health of the great big watershed above it. Generally speaking, the surface elevation goes up during and following wet years, and goes down during dry ones. Most famously, the lake’s level plummeted so far during the 2000-2005 drought that it left a 100-foot high bathtub ring, revealed treasures that had been submerged for decades and rendered many a boater’s guidebook obsolete. That big trough is apparent on this nifty graph I put together using surface levels in May and August of every year since Glen Canyon Dam’s completion (for 2012, I included average lake levels from every month thus far). 

What the graph doesn’t quite reflect, however, is the image, seared into many of our brains by the 2002 drought, of the ever-shrinking Lake Powell, a reservoir doomed by a climate that is getting drier and drier by the year. That prophecy (wish?) may yet come true, but for now the lake level trend is not a declining one, but a cyclical one, in which every dry period (and there were some doozies long before 2002) is countered by a series of wet years. There was even a rebound after the 2002 drought -- 2011 was one of the five wettest years in the last half-century. Had Glen Canyon Dam’s managers decided to hold back a bit more water last summer, they might have achieved even more of a comeback of the lake (instead, they were generous with their surplus, sending a lot more water down to Lake Mead than usual). As bad as 2012 has been, it has yet to wreck the comeback altogether. Lake levels held steady for most of the year, dropping off only in the past month. 

That’s not to say we shouldn’t worry about the climate. High temperature records are being smashed all over the place. Colorado and Wyoming had their warmest summers on record. During July and August, the high in Phoenix topped 100 degrees on all but 10 days, and on ten days during that period, the temperature never dropped below 90. And as I write this, the rivers feeding Lake Powell are at about half of their average flow for September. 

It’s just that, for now, we can’t hold up Lake Powell’s shrinkage problem as evidence that the region is dessicating. There’s also hope that things might get moist again, and that the cyclical pattern will continue. Buried in all the apocalyptic news is the fact that much of the Southwest had a wetter-than-average summer. The monsoons drenched southern Arizona and Nevada in August, and Las Vegas is getting flash-flooded as I type. 

Jonathan Thompson is a senior editor at High Country News. His Twitter handle is @jonnypeace.