Pat Mulroy on how Las Vegas (Nevada) plans to meet its long term water needs – desal! I know, I know, you’re saying, “But don’t you have to be by, like, an ocean or something?” Here’s the scheme: build big desal plant down on the Gulf of California, give that water to Mexico to meet their entitlement to the pittance of the Colorado that’s legally theirs, and let Vegas (and whoever else shared the cost of building the plant – some folks in Arizona also like the idea) use the water that would otherwise have gone to Mexico:

By 2020 I think we will have developed partnerships with Mexican entities for desalination plants and exchanging water on the Colorado River.

As far as the pipeline to bring water from Northern Nevada to Southern Nevada, you tell me what the hydrology in the Snake Valley Basin looks like in 2020 and I’ll tell you if we’re going there. If Southern Nevada has to fend for itself, I think we’ll have no choice but to develop that water supply. We can’t desalt our way out of this problem; the solution has to be larger and more dramatic.

As long as water supplies on the Colorado River stay relatively stable, Southern Nevada has lots of opportunities for water exchanges and desalination. But if climate scientists’ worst-case scenario on the Colorado River were to materialize and lake levels were to drop significantly, this conversation would change dramatically.

(Note to non-New Mexico readers: We have a “Las Vegas” in New Mexico, a lovely little down on the east slope of the Sangre de Cristo mountains. Hence my habit of clarifying which Vegas I’m talking about.)

From Shaun McKinnon, a must-read story for water geeks on Arizona’s thinking about its water future – specifically where to get more (or use less?):

Drop 2 is no Lake Mead, the huge reservoir outside Las Vegas that holds Colorado River water until cities and farms in Arizona, Nevada and California need it. The new project is unlike almost any other on the river, designed not to store large quantities of water for long-term use but to hold smaller amounts for a few days or weeks.

It is a fitting symbol of the challenges of stretching a water source – the river – that has little stretch left in it and of the mounting costs to do so.

The reservoir is an attempt to wring every last drop of water from the Colorado. It will act as a catch basin, holding water that flowed past the last traditional dam on the river without a user ready to take it. That can happen if, say, a farmer in California’s Imperial Irrigation District requests water for a particular day and then it rains in the time it takes the water to flow south from Parker Dam, south of Lake Havasu City.

John Wesley Powell famously argued in the 19th century that the West’s political jurisdictions should be shaped around watersheds, rather than the often arbitrary rectangles that had been used to establish our governmental geometry as the nation moved across the great plains.

Azotea Tunnel beneath continental divide, Northern New Mexico, courtesy USBR

In an odd sort of way, we seem to be carrying out Powell’s wishes in reverse – using interbasin transfers to reshape watersheds to fit the boundaries of existing governmental jurisdictions.

Consider Colorado, where the water tends to be on the west slope of the Rockies and the people on the east. But what’s a mountain range when you’ve got modern engineering, as Chris Woodka explains:

The Continental Divide has been breached by ditches or tunnels a couple of dozen times throughout the state’s history, bringing over an average of nearly half a million acre-feet of water annually to the Front Range.

I’ve been thinking about this because because of a comment one of my water friends made suggesting that in some sense at this point you have to link vast areas of the west into a single giant watershed: Northern and Central California, thanks to the diversions to Southern California, which is linked via diversion to the Colorado River. In terms of diversions, Phoenix and Tucson are in some sense “downhill” from the Colorado thanks to the Central Arizona Project, as is Albuquerque via the San Juan-Chama diversion. And of course much of Colorado’s front range urban corridor, as Woodka explains.

Oddly, the one thing we might consider leaving out is the Colorado River Delta in Mexico, since no water actually gets there any more.