Rio Grande runoff forecast: 44 percent at Otowi

March – July snowmelt runoff on central New Mexico’s Rio Grande, which provides the bulk of the river’s water, is forecast to be 44 percent of the 1981-2010 average, according to a federal forecast out this morning. The measurement point for that number is the Otowi Bridge, which is on the road from Santa Fe to Los Alamos. It is down from a 55 percent forecast on April 1.

At San Marcial, the final measurement point before the river enters Elephant Butte Reservoir, the forecast is for 25 percent, with most of that runoff having already occurred.

Both measurements have a range of error, depending on the weather from here until the end of the runoff season:

  • Otowi: a one in ten chance of as much as 55 percent, a one in ten min of 35 percent
  • San Marcial: Max 53 percent (min yields a weird modeling error that makes it look negative, but you know that’s not possible, right?)


  1. i’ve noticed that NM has gotten a lot of swirlies lately (weather patterns that seem to focus on rotating around Alb.) i’m not sure how much rain has actually come from these though as what appears on radar may not actually be reaching the ground…

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