I keep asking my friends who manage municipal water systems in the West how low their communities’ water use can go. None of them really know, which is fascinating. Their customers’ water use just keep dropping.

I’ve been following a couple of communities particularly closely – Albuquerque (because it’s my home town) and Las Vegas (the focus of a lot of my research attention for my book). The two communities also are a useful comparison because both do accounting in a sufficiently similar way that I’m able to do reasonable apples-to-apples comparisons. (Municipal comparisons are a notoriously difficult problem because of different accounting approaches, especially with respect to effluent return flows.)

In 2014, water use in Las Vegas dropped dropped another 3 percent, to 205 gallons per capita per day, part of a long, steady slide. It’s dropped 38 percent in the last decade. I don’t have good 2015 Las Vegas data yet, but based on the preliminary Bureau of Reclamation reports, it looks like consumption of Lake Mead water in Southern Nevada in the first nine months of this year is down another 1.5 percent from the same period last year.

Empty Albuquerque swimming pool, using less water. by John Fleck

I just got Albuquerque’s numbers for the first nine months of the year, which are down 3.4 percent from the same period last year. That should put us at somewhere between 130 and 131 gallons per capita per day this year, a 48 percent reduction in water use per person since 1995.

This kind of reduction in per person use of a critical resource is astounding, and says two important things, I think. The first is that we were pretty profligate with our water use until quite recently. The second is that it’s still not clear where the water conservation floor lies.

Note on data for the water nerds: These numbers are based on total withdrawals. My calculations for consumptive fraction: Albuquerque 55 gpcd, Las Vegas 120. See here for background on the difference.