Tilting carefully at the reuse windmill

Folks at the newly formed New Mexico Mercury are taking on New Mexico’s water problems in a big way, which I applaud.

But, as gently as I can do this, I need to engage them on what I think is a critical issue: their reuse argument: Here’s VB Price:

For New Mexico to get its water house in order, we need to … [a]ppropriate funds to subsidize the creation of urban gray water and black water treatment and recycling systems, on an individual scale and on a city-wide scale.

Also at the Mercury, Hana Wolf argued in a piece earlier this week for the reuse model.

I believe their argument is based on a faulty premise – that sewage effluent in New Mexico’s largest cities, especially Albuquerque, is water wasted, and that cleaning it so that it could be reused would end that water waste.

I took a crack at this question a couple of years ago in the newspaper.

As a National Academy panel argued in a report last year, there is a critical distinction between municipalities (primarily coastal ones) that simply throw away their effluent (usually by dumping it in the ocean) and inland cities that treat their effluent and return it to the system (primarily their rivers).

Places like Singapore and lately San Diego have made extraordinary progress with potable reuse. See my friend Cynthia Barnett’s Blue Revolution for a great look at the Singapore story, and the new Carpe Diem West report (pdf) for a look at where San Diego’s reuse fits into a broad new strategy. But that stuff’s happening on the coast, where all the real reuse action is, and should be. As the NAS report explains, inland reuse is a much more complicated problem because inland cities are generally putting their effluent in a place where it is already being reused:

If one’s experience with water reuse is in a water-scarce coastal city, one might assume that it is desirable for water to be treated and reused before it is released to the ocean. However, in an inland environment, water reuse may affect downstream users of the effluent.

In Albuquerque, every flush of my toilet makes its way down to the Albuquerque Bernalillo County Water Utility Authority’s southside treatment plant, where it is cleaned up and returned to the Rio Grande. From there, it flows south. During a dry irrigation season, much of it is diverted at the Isleta diversion dam for use by downstream farmers, or flows on down the river, feeding a riparian ecosystem and eventually ending up in Elephant Butte Reservoir, where it is then available for use by farmers growing chile and pecans down in the southern part of the state.

My toilet flush is already essentially 100 percent reused. It’s true that if we reuse, that means withdrawing less water from the groundwater/surface water system. But because we also return less to the river by an equal amount, it’s a zero sum game. There may be benefits, but reducing water consumption is not one of them.

For those trying to rationalize New Mexico’s screwed up water management system, there’s a big risk here. Sewage reuse would take an enormous amount of political, managerial and economic capital, all of which are in limited supply in this poor state. If it doesn’t really save much water, it takes those resources away from efforts that will save water.

Thanks to Michael Morrison, whose useful questions on Twitter led me to clarify the post.


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