Climate Change on the Colorado: The Devil In the Details

udpate: full column here (sub/ad req)

When I first began seriously trying to sort out New Mexico’s place in the scheme of Colorado River water management, I kept banging unsuccessfully up against what seemed like a simple question: If long term drought or permanent climate change reduces the river’s flow, how would the shortage be sorted out? Who, in other words, would have to use less water?

I take a crack at an answer in tomorrow’s newspaper (I’ll add a link when it’s up, in the meantime here’s a blog post teaser), via a new analysis by Doug Kenney at the University of Colorado (pdf of the study here).

As I explain in the column, Kenney makes a straightforward argument: that to the extent climate change or long term drought reduce total flows in the Colorado, the four upper basin states are responsible for reducing their use. California, Arizona and Nevada might have problems of their own (they’re overusing what Colorado River water they get as it is now), but they would not face a climate change-induced cut.

The framers of the Colorado River Compact, it has long been known, made a fundamental mistake in assuming that the Colorado River would reliably supply 16.5 million acre feet of water per year, and dividing it up accordingly – 7.5 million acre feet for the upper basin states, 7.5 million for the lower basin states and the rest for Mexico (actually that “rest for Mexico bit” came later, but it’s part and parcel of the underlying idea of a stationary supply).

Turns out there’s less.

SNWA Tunnel Boring Machine

Southern Nevada Water Authority Tunnel Boring Machine, being used to excavate a new, more reliable Lake Mead water intake for Las Vegas water supply as Colorado River levels decline

In the 11 years since 2000, the Colorado has averaged just 12 million acre feet per year, according to the U.S. Bureau of Reclamation. In a sensible world, the shortage would be divided equally among the parties – say, in round numbers. 5.5 maf for the lower basin, 5.5 maf for the upper basin, and 1 maf for Mexico.

But the compact was not written that way. In addition to the 7.5-7.5 split, the Compact has this to say about the upper basin’s water management obligations:

The States of the Upper Division will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75,000,000 acre-feet for any period of ten consecutive years reckoned in continuing progressive series beginning with the first day of October next succeeding the ratification of this compact.

As I explain in tomorrow’s column, that “will not cause … to be depleted” line is the sort of thing clever water lawyers will salivate over, sufficiently rich with ambiguity that legal hijinks are sure to ensue. But the risk is that the court will agree with Kenney’s interpretation (and that of most legal scholars) – that the upper basin must deliver 7.5 maf a year no matter what.

That changes the arithmetic. Even if one assumes a reduced share for Mexico, in a 12 maf per year world, you get:

  • Mexico – 1 maf
  • Lower basin – 7.5 maf
  • Upper basin – 3.5 maf

As Kenney puts it:

[T]he Upper Basin apportionment is essentially the last priority on the river, and as average flow volumes decline, this apportionment bears the full brunt of the “squeeze” of reduced water availability.

Some additional links:

  • The Colorado River Compact (from the USBR’s great Law of the River web  page)
  • The 12 maf average for 2000-11 comes from the USBR’s draft Annual Operating Plan for the 2010-11 water year (pdf)
  • Kenney’s report (pdf), which is a must-read for anyone interested in the institutional issues surrounding the problems we face on a river that is already over-subscribed, even before climate change


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  2. I’m not sure that there was a mistake. The way I’ve heard the story, the Lower States bargained hard for the 7.5 MAFY average because they felt that they had the senior rights.

  3. I’m with Francis. The lower basin states wanted rights to the river determined by prior appropriation because they knew they would be able to put their water to use before the upper basin states – CA was already well on their way in the 20s. What they came up with in the compact is some sort of compromise between PA (recognizing PPRs and permitting the lower basin to increase its beneficial consumptive use) and correlative rights (7.5 maf to each basin with commitment to Mexico shared equally). The 10 year rolling average was indicative of the belief that there was sufficient water in the system that occasional shortages would be made up by occasional surpluses (and possibly some recognition that it would be difficult for the upper basin to ever fully use its apportionment – not sure they envisioned the amount of out-of-basin transfers that has occurred). Also, how do the shortage sharing agreement and the current operational guidelines for Powell and Mead alter the requirements of the compact? Do they mean we all just look the other way if the 75 maf requirement is not met because it conflicts with other agreements?

  4. And one more thing. Looking at the compact, I wonder about the phrase in Art. III(e) that “the States of the Lower Division shall not require the delivery of water, which cannot reasonably be applied to domestic and agricultural uses.” Not to shoot my own state in the foot, but how does groundwater recharge pass muster under that restriction?

  5. Sure. But that was a long time ago.

    The Kenney paper talks a lot about equity. And as an occupant of Southern California, there’s lots of different ways to see what’s equitable. IID generates an enormous amount of low-cost food. Is it ‘equitable’ to the people who eat that food to reduce IID’s share so that a new development can get built in Colorado?

    Los Angeles is an enormous economic engine for the entire country, paying out a lot more in federal taxes than it receives in federal benefits. Is it ‘equitable’ to squeeze LA so that relatively poor states can engage in new growth?

    As a negotiator for any California interest, I’d take a pretty dim view to giving up the 7.5 MAFY requirement without getting a lot in return. As water law requires, we put our water to valuable economic use while you Upper States let it go. Now that the river’s in trouble you want to renegotiate? You slept on your rights, guys, and we have the delivery requirement. Seems to me you’re negotiating from a position of great weakness.

  6. Francis and Chris –

    Thanks for the great comments.

    I’d be curious what the two of you think of the legal argument one hears up here frequently: that “will not cause … to be depleted” refers to depletions by water users in the upper basin, and if climate change or drought are doing the depleting instead, the provision doesn’t apply?

  7. Not much. The CR has always been tremendously variable; hence the need for two huge dams and the provision that the delivery obligation is averaged over a decade.

    If total inflow to the Upper Basin plus storage in Lake Powell is less than 75 MAF over a decade, then the Upper Basin states have a really good impossibility argument. But that would require their take from Powell over that decade to be zero. So long as the Upper States take the first drop from the system (and oh how we can argue what the ‘system’ is), I think they are ‘causing’ the flow at Harper’s Ferry to be depleted.

  8. John – are you proposing we have a discussion about how we should determine what percentage of a given level of depletion might be from use vs. from climate variability? Has the upper basin “caused” any depletion attributable to climate change? Clearly not, but, as I’m sure Francis knows, causation is a really slippery issue when lawyers get their hands on it. And it’s not much better in the hands of scientists. I happen to think the compact language is pretty clear, in that the upper basin is obligated to send 75 maf down to the lower basin every 10 years. And in 1922, the only possible cause for not meeting that requirement was use by the upper basin. I don’t think there was a force majeure clause in the compact. I’d just say that at this point I would be extremely wary of relying on the availability of additional diversions (esp. out of basin) to supply further development in the upper basin.

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