New Mexico Water Resources Research Institute

New Mexico Water Resources Research Institute

The long view: Bridging the gap between future projected water demand and supply in the Middle Rio Grande

New Mexico is likely to face a significant gap between supplies of water, energy, and food by the next century. That’s the conclusion of Howard Passell, a Sandia National Laboratory scientist, and a group of colleagues, working to assess the impacts of climate change and population in the years ahead.

Careful not to call the conclusions “predictions,” Passell said the modeling results do offer a point of departure for discussions of the future. Speaking on a panel at the 57th Annual New Mexico Water Conference titled “Building a Plan,” Passell told the audience that state residents will face hard choices including severe measures “not yet on the table” should the model scenarios become reality.

 

Howard Passell, Sandia National Laboratories

An examination of technologies now being investigated to bridge the supply-demand gap shows that most are “incremental,” Passell said. But increasing capacity with sure, but small steps, won’t be enough. “We’re not on track to get us where we need to be,” he said. “We need transformational solutions.” Most current solutions simply shift the gap, but do not eliminate it.

In one case study, researchers from Sandia and the Bureau of Reclamation looked at climate change impacts in the upper and middle Rio Grande valleys on stream flows, reservoir levels, and meeting downstream treaty obligations. The team used several climate variables and 112 computer runs with 16 different general circulation models to arrive at a conclusion.

The average model run suggests that on the basis of climate change alone—without increases to population, added water conservation, or any changes to current water operations factored in—New Mexico could end up running two million acre-feet short of its obligations to the Rio Grande Compact by 2100. “That will never fly, of course, so something has to be done,” Passell said.

One possible solution would be to cut agriculture by 50 percent in the middle Rio Grande Valley, to about 25,000 acres. Using the models to evaluate this approach reveals that such a measure will make up the deficit. “We can fix the compact problem, but it creates another problem,” Passell said. “That is, we lose a lot of agriculture.”

Another possible solution is to use water dedicated for the bosque, or wetlands along the river. By cutting the bosque in the Middle Rio Grande from 60,000 acres to 20,000 acres, the compact demands can be met, according to the computer models. “We no longer have a gap in terms of the compact, but we’ve created another gap because we’ve lost the bosque,” Passell said.

Another possibility looked at was lining about 80 percent of the Rio Grande between Cochiti Reservoir and Elephant Butte Reservoir by 2100. “That will solve the deficit, but we are just moving the gap because by lining the river with concrete we don’t have leakage from the river to the shallow or deep aquifer, we lose the bosque, or part of it, and reduce aquifer recharge, and so on,” Passell said.

Preliminary conclusions of the case study show that these measures, reducing agriculture or wetlands, or lining the river channel can solve the compact deficit problem. “But they lead to many other kinds of gaps and we end up with many shortages and problems,” he said.

 

Model results show river deliveries going down over time as a result of climate change alone, not including consumption from increasing population, and not including efforts at conservation or demand reduction. The authors of the study indicate that “Results are not predictions, but rather a starting point for dialogue and increased awareness of potential impacts of climate change.

Another scenario examined by others at Sandia as part of other projects was changing cropping patterns and irrigation methods instead of eliminating agriculture. If drip irrigation and production of vegetables replace flood irrigation and alfalfa and grass cultivation, almost as much water could be saved as by eliminating agriculture all together—although Passell points out that this just shifts the gap again to those who grow and use alfalfa and grass hay. “There is a virtue in maintaining agriculture in the basin because it addresses food security issues. Right now we import a lot of food from thousands of miles away. Instead of that we might cultivate our food in our own basin,” he said.

“Demand reduction in the end may be the only sensible solution that doesn’t shift the gap,” Passell said. To accomplish that, population growth control and dramatic changes in New Mexico’s water, energy, and food consumption would be in order, he said. Examples include more judicious agriculture, smaller and much more efficient homes and buildings and turning the thermostats down in winter and up in summer, changes in diet like less dairy and beef, fewer electronic gadgets and appliances. “Generally these topics have not been put on the table as possible solutions,” Passell said. “Too often these kinds of solutions are marginalized in favor of efforts to simply meet the ever increasing projected demand.”

“If we can’t meet demand, we are going to have to do other things. If we can reduce population growth, then we can move toward a steady state economy—one that doesn’t depend on constant growth.

Some of these things are pie in the sky and some might even say that these things are preposterous, but I would suggest that eliminating our natural capital, impairing the ecosystem services that have allowed us all to be here is equally preposterous,” he said. “We need to be looking outside the box for new sets of solutions. If we don’t have enough water to meet projected demand, maybe one of the things we have to do is reduce that demand in the future.”

New Mexico Water Resources Research Institute


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