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:
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.
pretty good forecast, in retrospect!
Wow, I’d forgotten!