Last week’s release of the Colorado River Basin Water Supply and Demand Study was a headline-grabbing event – “Colorado River water supply to fall short of demand, study says“, to cite but one of a zillion examples of the core message getting big play. Barry Nelson argued the study “has the potential to mark a new era in the management of the West’s largest river basin.”

Lee’s Ferry

We will see. As with most massive undertakings of this nature, the angels and devils are in the Basin Study’s details. And a separate, routine little US Bureau of Reclamation report that came out last week helps illustrate the point.

There were two big talking points. The first, the supply-demand gap, comes as no surprise to anyone involved in Colorado River management. To the extent this a big deal, its importance is the way the Basin Study loudly points out something that’s been painfully obvious for some time.

The second point, a bit more surprising to some (and also worth loudly pointing out), is that plain old water conservation is far more cost-effective, and quicker to implement, than big engineering solutions like building a pipeline to the Missouri. I chose to highlight these two points with the precious few words available for my newspaper story about the study.

But there’s something deeper in the Basin Study that’s worth exploring. (click through for wonky details)

Simultaneous to the great fanfare that accompanied last week’s release of the Basin Study, the Bureau of Reclamation also published the December version of the “24-month study” (pdf), a monthly report done by the agency’s hydrologists incorporating the latest planning scenarios for managing the major Colorado River Basin reservoirs over the next 24 months. Its 18 pages of mostly tabular data are updated monthly as a tool to inform basin water managers of the Bureau’s best current estimate of what is happening at the interface of weather, climate, hydrology and the Byzantine “law of the river” used to apportion the strained river’s supplies.

And it is at that interface, beyond the “OMG we’re running out of water!” and “soft path is the answer!” headlines that the Basin Study seems most interesting to me.

Given the supply-demand imbalance, the question to me has always been, “OK, if there’s not enough water in the basin, who specifically – which state, and then which municipal or ag water agencies within that state – loses water?” That question is then closely related to the “soft path” issues the Basin Study points to, because whoever specifically is losing water will also be the ones who will be forced to get real about using their water more efficiently.

The “law of the river” – the body of statute, compact, treaty and court decisions that governs the administration of the Colorado River – offers some general guidance in thinking about this question. The Basin Study offers some useful data in thinking about how the future might play out. And the current 24-month study shows what’s happening right now, in real time.

The Law of the River

The 1922 Colorado River Compact split the baby by splitting the Colorado River on paper into two equal-sized pieces, with “half” of the river allocated to the states of the Upper Basin (Wyoming, Colorado, New Mexico, Utah) and the other “half” going to the Lower Basin states (Nevada, Arizona and California). I put scare quotes around “half” because the Compact’s great blunder was to put a number on what was meant by half – 7.5 million acre feet for each basin. What happens if there’s less than 15 million acre feet per year (plus some 1.5 maf of spare change for Mexico) has been left as an exercise for later courts and lawyers.

The key for this discussion is that, as long as the Upper Basin delivers 8.23 million acre feet of water each year past Lee Ferry in Northern Arizona (7.5 maf for the Lower Basin plus the spare change for Mexico), the Upper Basin States will have met their legal obligation. Above Lee Ferry, it’s up to the Upper Basin states to sort out who gets what. Below Lee Ferry, it’s up to the Lower Basin folks to sort out who gets what.

The Basin Study

In my view, the most important thing in the Basin Study is Figure 22 on page SR-66 (page 76 of the pdf) – the risk, under decreasing supply and increasing demand, of water shortages at various points in the system. This is where the Basin Study starts getting specific about who’s gonna run short. (I’m not going to reproduce it here – go read if you’re interested.)

The numerical analysis is complex, but the figure makes two basic points:

• The risk that the Upper Basin will fail to meet its Lee Ferry delivery obligations over the next 50 years is low.
• Despite the Lower Basin getting its full legal entitlement as a result of Upper Basin deliveries nearly every year, the risk of shortages in the Lower Basin (across a number of different metrics) is high.

The 24-Month Study

So what’s happening this year?

With two months of the 2012-13 snow-growing season already behind us and a dismal crop of white stuff in the high country to report, the Bureau’s hydrologists, in the 24-month study, have started to constrain the range of possibilities. The result is a pretty droughty set of tables. But despite the grim forecast, the stockpile of water in Lake Powell, behind Glen Canyon Dam (and upstream of the all-important Lee Ferry measurement point) is plenty big enough to ensure that the Upper Basin states will meet their legal delivery obligation of 8.23 million acre feet. To meet that legal delivery obligation, Lake Powell is projected to drop 27 feet in elevation – 2.8 million acre feet in total storage.

And yet, despite getting a full allotment in the Lower Basin, Lake Mead is projected to drop more than 8 feet in elevation, some 800,000 acre feet.

The Problem

I don’t mean to gloss over some interesting Upper Basin problems to be found in the Basin Study. Supply-demand issues in the Upper Basin go beyond merely meeting a Lee Ferry delivery obligation. (OK, I do mean to gloss them over for now, but I promise I’ll get back to them.) But to the extent we’ve got a large-scale supply demand imbalance in the Colorado River, that lovely little Figure 22 shows that it’s primarily a Lower Basin problem. And it’s a problem because, even if the Lower Basin gets a full delivery every year, current usage down in the low countries of Nevada, Arizona and California is greater than the legally guaranteed supply. As I’ve written before (see hookers and blow on the Lower Colorado), if it weren’t for bonus water deliveries above and beyond the legally required 8.23 million acre feet Lee Ferry delivery, Lake Mead would already be dry.

So what does this view of the basin’s problems suggest going forward?

First, to the extent we decide to pursue big engineering solutions (you must read Bettina Boxall’s piece on towing icebergs), the bulk of the benefit is a Lower Basin benefit. It’s hard for me to imagine New Mexicans chipping in much to pick up the tab. So down this path lies a significant political argument over equity. (Unless, of course, we can get the federal taxpayers to pick up the tab!)

Second, to the extent we pursue the soft path of water conservation and other steps to maximize the utility of the use of the water we’ve got, this seems most likely to be carried out state by state and locality by locality. Water conservation is fundamentally a local activity, and it’s most often driven by a lack of supply. This may very well happen on its own, without any need for a great basin-wide conversation. Tell farmers or cities “Hey, not enough water” and they suddenly get thrifty.

Unanswered in all this is the question of environmental flows – water for the Basin’s rivers themselves. I don’t quite understand where that fits, and on that question the Basin Study isn’t much help. Suggestions welcome.