Pulling together some New Mexico water use numbers today for one of my University of New Mexico colleagues, I was reminded of a cool paper from a few years back by Peter H. Gleick and Meena Palaniappan of the Pacific Institute that contained this striking graph:
It’s two times series – U.S. gross domestic product and total water use – plotted side by side. As Gleick and Palaniappan note, the two rise “in lockstep” through most of history – as the nation grows, both in population and economic activity, so does its water use. But in the 1970s, the curves decouple. Our national economy has continued to grow, but our water use has not. Increasing population and economic activity no longer requires more water.
In the research I’m doing for my book, I see curves that look like this all the time. I’m more frequently looking at population growth rather than total economic activity, and I’m often slicing up the data to look at groundwater versus surface water withdrawals, municipal versus agricultural use, and ag water use compared to ag productivity. But looking at this in lots of different ways, I almost invariably find some sort of decoupling.
New Mexico water
Here’s today’s decoupling – municipal water use in New Mexico:
This particular USGS dataset is “public supply”, which is essentially all the state’s major municipal water agencies and captures 85 percent of the state’s population. Municipal use peaked in 1995. In Albuquerque, the state’s largest metro area (and site of my own backyard rain barrels), per capita use looks like it’ll be about half this year of what it was back then. If you add in agriculture (which in New Mexico uses ten times as much water as municipalities), New Mexico water use peaked in 1980. Both groundwater pumping and surface water diversions have been declining ever since, even as our state’s population and economy has grown. In inflation-adjusted terms, New Mexico’s ag sector was about the same size in 2010 that it was in 1980 (data from BEA), but it’s using a million acre feet per year less water. That’s a big part of how “decoupling” works.
Finding these points of decoupling and looking at the hydrologic and policy drivers is one of my new hobbies (where by “hobby” I mean “book research”), because they point to examples of what solutions to our problems might look like. If I can generalize, it’s the relatively straightforward notion that when people have less water, they get clever about using less water to get stuff done. Municipalities facing scarcity get the conservation bug, and farmers are just plain smart about adapting when they have less water to work with.
Arizona is a particularly interesting example. Despite a reputation for groundwater management problems, its groundwater use peaked in 1975, according to the USGS, and is now barely more than half of what it was then. A big part of that is the substitution of surface water from the Colorado River, but groundwater use has dropped more than replacement use of surface water has risen. Arizona’s 1980 Groundwater Management Act has its problems, but by this important measure (and others, especially rising aquifers in key parts of the state) it seems to be working. An annual reduction of more than 2 million acre feet per year in groundwater pumping seems like kind of a big deal. Phoenix, to cite one example, used to get nearly all of its water from groundwater. Now it gets almost none, switching from mining ancient and non-renewable groundwater to renewable surface water supplies.
According to the USGS data, Arizona’s overall “peak water” moment (ground + surface water) came back in 1980. Arizona’s population has more than doubled since then, and it’s using 25 percent less water, even with those crazy “misters” people install at outdoor restaurants and backyard patios to try to make Phoenix summers bearable.
This “when people have less water, they use less water” thing is one of the lines of evidence that makes me optimistic about our ability to solve our region’s water problems if we can identify the characteristics that make it work and harness them in the cases where we’re still having problems.
Note on sources: The data for my graphs (and also the one in the Gleick/Palaniappan paper) is the USGS water use report series.