In a typical year, runoff past the Otowi Bridge on the Rio Grande peaks in the last week of May, as warmer weather melts off mountain snow to the north.

This year, the peak came May 11, according to USGS data.

One obvious reason is the warm weather. Even with cool temperatures the last 10 days of May, the month as a whole was 4 degrees F above average in Albuquerque, with similarly warm temperatures. But scientists have identified what they think is a second reason: dust on snow. From a story I wrote that ran over the weekend in the Journal:

Dry weather since the start of January has contributed to an unusually large number of dust storms, and dusty snow absorbs more sunlight and melts faster, according to University of Utah scientist Tom Painter.

"It warms the snowpack earlier and then contributes to snowmelt earlier," Painter said in a telephone interview.  

I've been hearing about Painter's work for some time. Richard Harris did a piece three years ago on NPR, and it's cropped up in stories in the regional media ever since.This year's early runoff spike provided a good news peg to visit the issue for Albuquerque Journal readers, who have a special stake in the issue:

The rapid snowmelt is a potential problem for the system that captures water from the San Juan River basin and shuttles it across the Continental Divide to provide drinking water for Albuquerque.

The water flows through the 13-mile Azotea Tunnel. If it comes too quickly, the tunnel will be filled to capacity and any extra is lost, explained Steve Bowser, a hydrologist with the U.S. Bureau of Reclamation.

With warming temperatures predicted this century, along with drying in the lowland deserts that produces the dust, Painter and his colleagues predict more dust-induced rapid snowmelt.

Further reading:

• USGS data on the flow past Otowi 
• High Runoff Due to Dust, ABQJournal, May 28
• Richard Harris's NPR coverage of dust on snow