In the work I’m doing now on the Colorado River Basin for my book, I’m trying to get beyond simply extrapolating supply and demand curves and then running around with my hair on fire. The hair-on-fire thing is easy to do, because the current supply and demand curves, as the Bureau of Reclamation frankly noted last December, are heading in a direction that’s physically unreal.
The question is what happens in the gap between the projected orange line veering upward and the blue line veering down. I’m interested in the specifics of that failure mode – who will come up short as the gaps between supply and demand become real, and how might we expect them to respond? It’s not enough to simply say “Phoenix (or Las Vegas or Los Angeles or Denver or the Imperial Irrigation District or Albuquerque) is screwed.” Because those water users will do something in response to try to minimize their screwedness. Who are they, and what will they do in response?
Buried in the tiny print of the US Bureau of Reclamation’s latest 24-Month Study (pdf) is a hint about what seems to me to be the most likely answer to my “who” question: Las Vegas, look out. (warning, wonkiness ahead, click through for more)
The Bureau doesn’t use red ink in its 24-month studies, a monthly compilation of stats on how much water there is in the basin now, where it’s sitting, and how much is expected based on the latest forecasts over the coming year. But red ink would be appropriate in this month’s edition. By this time in the spring, we’ve got a pretty good idea of what the current water year looks like, and it pretty much looks like a supply disaster:
Observed unregulated inflow into Lake Powell for the month of April 2012 was 0.764 maf or 72 percent of the 30-year average from 1981 to 2010. The forecast for May 2012 unregulated inflow into Lake Powell is 0.650 maf or 28 percent of the 30-year average. The forecasted 2012 April through July unregulated inflow is 2.36 maf or 33 percent of average.
Last year’s huge bounty of bonus water lifted total storage in the reservoirs behind Glen Canyon and Hoover dams by 5 million acre feet. 3 million of those acre feet will disappear this year.
The big picture Colorado Basin failure mode most often discussed is the “compact call”, the legal moment when the states of the Upper Basin fail to deliver their legally mandated 7.5 million acre feet (plus some spare water for Mexico) at Lee Ferry. Doug Kenney lays out a dandy failure mode in his discussion of the “climate change squeeze”, in which Upper Basin states, in order to meet that requirement, would have to curtail their uses of a Colorado River shrunk by climate change. I think Kenney’s argument is basically right (or at least, not obviously wrong).
But it is worth noting that even during the kick-ass drought of the ’00s, and continuing this year, the Upper Basin states have been able to meet their 7.5-plus maf delivery obligations (8.23 maf after water for Mexico is added to the ledger) and then some. From the perspective of the Lower Basin, there’s been no drought at all. They’ve continued to get all they’re legally entitled to, and then some.
And again this year, the 24-month study calls for delivery of another 9.5 million acre feet at Lee Ferry, more than enough to meet the Upper Basin’s legal requirements. And yet despite getting bonus water again this year, Lake Mead is projected to drop once again by the end of the 2012 water year, down 2 feet in elevation. That simple 2-foot drop is the number that I think matters the most, the tiny print I was referring to earlier. What’s going on here?
I’ve fallen back on this slide many a time on the blog to explain. Basically, the Lower Basin states – California, Arizona and Nevada – are legally entitled to use more water than flows their way each year under the minimum legally required scenario:
Basically, what this simple water budget calculation suggests is that, given the minimum legally required inflow, there’s a 1.2 million acre foot per year shortfall among California, Arizona and Nevada, the states that use water flowing out of Lake Mead. That translates to a (roughly) 12 foot drop in the lake’s surface elevation. Mead’s projected to end the year at a surface elevation of 1,114 feet above sea level. When it hits 1,075, the reservoir’s operating rules, on which all seven basin states and the federal government agreed, call for Arizona and Nevada (basically Las Vegas) to face curtailment. (California stays fat and happy, having the senior-est rights on the Lower Colorado).
Arizona and, to a lesser extent, Nevada, have some room to move. Arizona is currently banking some of its surplus Colorado River water underground, along with a lesser portion for Nevada. But Arizona has a lot more room to move when it comes to agricultural usage. I’ve flown in and out of Phoenix a couple of times recently, and there sure is a lot of cotton still growing on the outskirts of town. I think it’s reasonable to think Arizona will figure out some equitable way of compensating farmers for some of that water when that shit hits the fan.
The Southern Nevada Water Authority, which serves Las Vegas, doesn’t have the ag cushion. It also faces a second problem. Independent of its legal rights to water from Lake Mead, it also has physical constraints. As the reservoir drops, its surface gets closer to Las Vegas’s water intakes, which are big pipes into the reservoir itself (Arizona takes is water downstream, so doesn’t face this problem). Vegas is hurriedly building a “third straw” – a new intake that is far deeper in the lake.
It’s reasonable to think that Vegas will get the new intake done ahead of the dropping lake. (If it’s doesn’t, the intake problem is the failure mode we all need to pay attention to). But it’s less clear that the Lower Basin states have the institutional mechanisms in place to sort out the question of who’s entitled to how much water if Mead keeps dropping despite the Upper Basin continuing to deliver its legally mandated 8.23 maf per year.
So my vote goes for the Lower Basin Crunch being the first failure mode we’ll see. And given Arizona’s flexibility in dealing with what comes next, it seems to me that Las Vegas is the place to watch for the first serious signs of trouble.