Draining the reservoirs on New Mexico’s Rio Grande

A rapidly drying Rio Grande at Albuquerque, Sept. 9, 2018. Photo by John Fleck

tl;dr

Total reservoir storage on the Rio Grande in New Mexico at the end of August was the lowest it’s been since at least 1980.

longer (with graphs!)

In our University of New Mexico Water Resources Program class, we’ve been discussing the state of the Rio Grande in real time. This feels like a remarkable moment, for teaching.

The water managers down on New Mexico’s Lower Rio Grande have made the conscious decision to essentially drain Elephant Butte Reservoir – the primary source of surface water supplies for farmers in the Hatch and Mesilla valleys. Elephant Butte, a 2 million acre foot reservoir, ended August with just 85,000 acre feet of water, something like 4 percent of capacity. That’s the lowest it’s been at this point in the year since 1972.

Simultaneously, we’ve made a similar decision upstream – draining Abiquiu, El Vado, and Heron reservoirs on the Rio Chama in order to continue deliveries to farmers in this part of the state, with some water devoted to instream flows for the endangered Rio Grande silvery minnow.

We essentially manage the two parts of the system separately, but I was wondering what it would look like if we looked at them together:

Combined end-of-August storage in Heron, El Vado, Abiquiu, Elephant Butte, and Caballo reservoirs

The US Bureau of Reclamation datasets available on a Sunday afternoon lack the necessary detail prior to 1980 for some of the reservoirs, so that’s as far back as the graph goes.

We’re draining these things and hoping for a wet winter.

7 Comments

  1. Not sure whether Van Clothier statement is correct, but it probably makes sense to drain reservoirs to a minimum rather than overdraw from aquifers, as evaporation is very significant and will be increasing with hotter summers due to global warming. It would be interesting to have data on monthly groundwater withdrawal from urban areas, and to see cities start to move toward subsidizing rainwater harvesting and increasing reclamation of wastewater rather than overdraw from aquifers, which risks draconian measures be taken.

  2. Van – I’m curious about your source.

    The most recent New Mexico Office of State Engineer “Water Use By Categories” report puts reservoir evaporation at 262,000 acre feet per year, as compared to 3 million acre feet per year for agriculture, and 317,000 acre feet per year for municipal use.

  3. Mild comment on the graph: would be nice to see a maximum possible storage line, as well as lines at the half-maf measures as well as at 5-year increments. Kinda hard to see what falls where or make comparisons in this (which is still pretty cool).

Leave a Reply

Your email address will not be published. Required fields are marked *