(originally published 2012)

Ninety years old this year, the Colorado River Compact is more relevant and consequential than any time in its history. That says a lot. Sharing water within its collaborative, progressive framework, the Southwest blossomed, and its sustained influence on our current water dialogue is immeasurable.

Indeed it’s more than an interstate agreement. It’s a way of life, not to be trifled with carelessly. Arizona Senator John McCain was reminded of this in 2008 when he was roundly thrashed on the campaign trail for suggesting the Compact be renegotiated. (Though Arizona has never been thrilled with the Compact).

It’s also an agreement that’s largely ignored in a surprising way.

Turns out the Colorado River has never really been divided as the Compact authors envisioned. At least as much as we can tell. The legendary treatise, constructed to apportion the prodigious fruits of the Colorado River equitably between the Upper and Lower River Basin, really hasn’t.

In 1922 legislators divided the Colorado River roughly in-half, in theory, requiring the Upper Basin, the headwater states, to send 7.5 million acre-feet of water downstream on average every year past Lee Ferry’s, Arizona, to users in the Lower Basin. It was assumed based on information available at the time that about the same amount would remain for use by Colorado, Wyoming, Utah, and New Mexico.

But Eric Kuhn of the Colorado River Water Conservation District cites Bureau of Reclamation data that indicates usage has been far different. Over the past fifteen years, for example, “Lower Basin Consumptive Uses” has been around 11,000 million acre-feet per year; uses by the Upper Basin, roughly 4 million acre-feet. It’s a big discrepancy from the Compact parameters. The River tilts to the southwest – in more ways than one.

This imbalance may have been agreeable in the past. Not anymore, for two reasons.

One is demand. There used to be plenty of water to go around. However much water rose in the headwaters of the River was enough. A precise accounting wasn’t really necessary. The other is information – data. Usage throughout the River system is far better understood, and more data is coming. This will enable states, in this new era of scarcity, to track supply and call on the resources of the River more accurately. As a result, any notion of a River-wide surplus is disappearing. And with it any casual, generous interpretation of the terms of the Compact.

Of course states, not the Basins, will press the case to revisit apportionment of the River given the imbalance, and Colorado may stand to gain as the River is more accurately measured. The Compact allocated 51% of the Upper Basin share to Colorado, or 3.6 million acre-feet annually. Kuhn estimates that last year, in 2010, the state tapped the River to the tune of about 2 million acre-feet.

Is Colorado therefore entitled to more water per the Compact? In theory, yes. In practical terms, maybe. In the estimation of some, including voices in the environmental community, no.

Kuhn’s District is one influential voice advocating very deliberate action relating to a possible Colorado surplus. CRWDC makes their case for caution in a thorough, authoritative report released early this year. (Read it here.) The CRWCD simply doesn’t believe water’s available in the long run, guessing that any additional supply Colorado might be entitled to is illusory. The CRWCD sites a diminished River as evidence.

Data indicates that in the early 1900’s, when volume was measured for purposes of dividing the River, conditions throughout the Basin were unusually wet. Recently, drought has been the norm. Like others, they’re also concerned that climate change will lessen the amount of future precipitation in the region. It adds up to a total volume of water less than the 15-18 million acre-feet Compact authors divided in the first place. As the first obligation of Colorado and other Upper Basin states is to send 7.5 million acre-feet of water downstream every year, plus a little more for Mexico, Colorado’s 51 percent share would be calculated from a smaller total. In this new calculation, its surplus evaporates. Literally.

It’s the potential of developing more water only to have the supply curtailed, reversed after users come to rely on it that leaves the CRWCD uneasy (if I read their report correctly). Imagine cities that come to rely on a new supply only to have it cut-off.

Nevertheless others here and throughout the Upper Basin would move aggressively to grab more water and let policy-makers catch-up to new information that for now seems to indicate there’s room for a revised apportionment upward. As risky as some think this strategy may be, if it’s shown that more can be done to capture and use water allocated under the terms of the Compact, officials in water-challenged communities or states may choose to pick-up where Senator McCain left-off.

And the Compact, in its 91st year, will yet again prove its relevance.

More from the pro-development camp next time.