El Niño and New Mexico’s Rio Grande

Does the looming El Niño mean we can expect a big year on the Rio Grande? Not necessarily. The scatter in the data is huge, but hidden in the data is a bit of a nudge in the direction of wet:

El Niño vs. Rio Grande flow in New Mexico

El Niño vs. Rio Grande flow in New Mexico, analysis by John Fleck, UNM Water Resources Program

That’s native flow at Otowi, the key Rio Grande measurement point north of Albuquerque. There’s a statistically significant relationship – El Niño years get more flow (p = 0.01). But the effect is small (R^2=0.1). So best to say that El Niño has a small positive effect overlaid on a huge amount of regular variability.

All five of the biggest El Niño years in my dataset were wet, but that’s such a small sample that you should wag your finger at me for even pointing it out.

The horizontal black line is the median of the dataset.

Data sources and notes:

  • Otowi Index Supply from New Mexico Interstate Stream Commission that I happened to have laying around (OIS is the actual gaged flow at Otowi minus the imported San Juan-Chama water)
  • El Niño historic data from Klaus Wolter’s Multivariate ENSO Index. I used mid-winter Dec-Jan MEI. Eyeballing the data, the choice of months doesn’t seem significant, but see “limitations” below.
  • Years plotted 1950-2012


  • I was a philosophy major in college.


Comments are closed.