River Beat: Why Is Lake Mead Dropping?

Easy answer to the question asked in the title of this post, right? The last decade is the driest 10-year stretch since record keeping began on the Colorado River. Of course Lake Mead has dropped because of “drought”, right?


Lake Mead from Hoover Dam, April 2010

Lake Mead from Hoover Dam, April 2010

During that entire time, thanks to upstream storage and the fact that Upper Basin consumption is still relatively low, Lake Mead continued to get its entire allotment of water every year as required under the Colorado River Compact. Each and every year, 8.23 million acre feet was released from Lake Powell downstream through the Grand Canyon to Lake Mead. That’s the Upper Basin’s Compact-mandated delivery of 7.5 million acre feet, plus the Upper Basin’s share of the U.S. obligation to Mexico under the Treaty of 1944 (pdf). In fact in one of those years, 2008, Mead got extra.

Lake Powell, the upstream of the two great Colorado River reservoirs, responds to climate. Lake Mead responds to human management.

Here’s a bit of arithmetic, courtesy Paul Miller, a Bureau of Reclamation hydrologist who spoke at the Lake Mead symposium I attended last month in Las Vegas:

Lower Colorado River Basin Water Budget

When you count inflow downstream from Lake Powell, Lake Mead gets 9 million acre feet of water a year. It dispatches 9.6 maf of water a year to cities and farms downstream. Another 0.6 maf evaporates from the desert lake’s sun-cooked surface.

In other words, under normal operating conditions, Lake Mead is overdrawn by 1.2 maf per year.

Like Blanche DuBois, the Lower Basin has very much depended on the kindness of strangers – in this case, folks in the Upper Basin who have not yet used their full share of the river under the Colorado Compact and have for years been sending the extra down the Colorado River.

In fact, Lake Mead’s steady decline dates to the late 1990s. That is when the Central Arizona Project first began taking its full allocation. That is when the overdraft began.

This is the explanation that arose when the University of Colorado’s Doug Kenney and his colleagues compared the drought of the ’00s with the hypothetical drought used in the famous Severe Sustained Drought case study published in 1995.

In the SSD study drought, Powell declines first, and Mead’s levels hold steady. But when Kenney and his colleagues (Rethinking Vulnerability on the Colorado River, Journal of Contemporary Water Research and Education, Issue No. 144, March 2010, pdf here) compared the SSD drought to the real one we’re now experiencing, they found both reservoirs dropping. Why did the SSD get it so wrong? Because of the completion of the Central Arizona Project (CAP), which finally allowed Arizona to consume its full legal Colorado River allotment:

The project was “substantially completed” in 1994, and very quickly was put into full operation. Mainstem deliveries to Central Arizona Project averaged 1.5 maf/year from 2000 to 2004, roughly 3 times higher than the Central Arizona Project demand projections used in the SSD study (derived from assumptions in the 1991 Annual Operating Plan and economic modeling that assumed Central Arizona Project water would be prohibitively expensive for many users).

The result, as Emily Green noted today, is that Mead’s surface elevation is back under 1,100 feet as of the end of April.

I don’t think you can point a finger of blame here at anyone in particular. In fact, as a journalist, that’s the most interesting thing about this issue to me. No one person or entity is in charge of the Colorado. Instead, you have this fascinating collective management going on, involving complex and subtle interactions among the Bureau of Reclamation, the seven states, and the water agencies, all constrained by the somewhat rigid but nevertheless evolving “Law of the River”. It’s precisely the sort of collective management of a common-pool resource that Elinor Ostrom talks about.

It’s also not helpful, I think, to go all Cadillac Desert and blame Floyd Dominy and the engineering culture of the 20th century. We’ve got the dams, canals, farms and cities that we’ve got.

In answer to the question posed by this post’s title, I guess one could argue that a climatological drought is at least partly to blame. If it had been wetter over the last decade, there would have been extra in the Upper Basin, and some of that bonus water would have sloshed on down through the system to Lake Mead.

But depending on surpluses does not sound like a sound long term management strategy.


  1. Nice post, and I’ve enjoyed the series very much (thank you), except here I’m confused. I don’t get the set up. You begin: “The last decade is the driest 10-year stretch since record keeping began on the Colorado River. Of course Lake Mead has dropped because of “drought”, right? No.

    But you come back round to drought.

    It’s interesting and always important to explain that Mead is dropping because of what is quaintly called “over-allocation” (a problem that has been known since at least the 1960s and AZ vs California). And it’s always good to hear someone point out that the Southwest grew on borrowed surplus water. That point can’t be made often enough.

    But it does not negate the fact that since 2002 inflows to the system have been at their lowest since measurements began and that climate modeling predicts runoff to shrink, making the original allocations even more wildly optimistic. If a sharp drop in normal streamflow is not drought, what is it?

    This is all a long way of saying I don’t think your straw dog worked, though what you were saying was still very interesting.

    I’m also confused by: “It’s also not helpful, I think, to go all Cadillac Desert and blame Floyd Dominy and the engineering culture of the 20th century. We’ve got the dams, canals, farms and cities that we’ve got.”

    I don’t know anyone “going all Cadillac Desert,” though I’m sure there are old time holdouts who still think of dynamite when they look at Glen Canyon Dam. On the Public Record blog, which along with yours and WaterWired’s are several of my favorites, also takes regular jabs at Reisner-ites and I’m sure that from a water-management standpoint those who want time-travel back to Muir’s day get more than a little bit irritating.

    But enough already. Moreover, a word of defense for an author who didn’t drink Reclamation’s Kool Aid, or the Army Corps’. Reisner’s book did an inimitable job pointing out what got us pretty much exactly where we are. He’s just as dead as Dominy, deader, and both men looked at rivers through distinct prisms, but why the pause to bow to Reclamation’s cortege instead of NRDC’s? Especially when you’re essentially pointing out problems illustrated by Reisner’s book? The water world is very much the poorer for Reisner’s 2000 death from cancer. He would have been the first writer I’d have wanted to read when both main storage reservoirs on the Colorado tanked in the drought (whatever you want to call it) of 2002 and the Southwest began to look at the upper basin states’ allocations with wolfish eyes.

    The Lower Basin’s implicit expectation, since it grew up fast and first, is that as shortages grip the system, its existing cities will need priority as management of the river evolves. The Upper Basin doesn’t seem to interested in this and is moving to develop the water at ever more northerly points. At the risk of sounding “all Cadillac Desert,” where do we go from here?

  2. Emily –

    Great comments, and I think you have to some extend exposed a weakness in both argument and its execution. You’re right to say that drought is, in fact, relevant here, and can’t be ignored. But to date it has had little effect on the level of Lake Mead. To the extent that politicians in Las Vegas or Phoenix or Los Angeles blame “drought” for the problems they face as Mead declines, they are misleading their constituents.

    When you say “If a sharp drop in normal streamflow is not drought, what is it?”, it’s important to distinguish between Lake Mead and the basin as a whole. From the vantage point of Lake Mead, there has been no “sharp drop in normal streamflow”. There has been no drop in streamflow on the main stem of the Colorado River into Lake Mead at all. Upper Basin storage and under-utilization have buffered the Lower Basin entirely against the effect of drought. This is the central point Kenney et al. make. Drought effects Lake Powell, by reducing the amount of incoming water. But the Compact obligation to deliver 8.23 maf no matter what has thus far meant that Mead has been able to rely on a supply that has not been reduced as a result of the ongoing drought. Even in the worst years of the drought, 2002-04, Mead got its 8.23 maf like clockwork. Lake Mead’s drop is a function of demand, not supply.

    As for my “Cadillac Desert” quip, I was too snarky for my own good. My point is that we could (and often do) spend a lot of time arguing about whether the 20th century engineering approach to managing water was good or bad. But the fact is this is the system we’ve got.

    Re where we go from here, it seems clear to me that one of the key things that has to happen is that people in the political institutions that manage water in the lower basin need to stop blaming “drought” – nature, in other words – and take ownership of the real problem, which is an excess of demand. This is where drought matters a great deal, now and going forward, because it means the buffer is gone.

  3. The simple fact is that the resource is overused. SNWA’s Pat Mulroy and many others blame drought as an excuse to further their own programs – in Mulroy’s case, the drive to desertify 100,000 square miles or so of her home state in a water mining scheme that, at best, kicks the can down the road a few decades. Those programs in Nevada and among all the Basin states are designed to pump profits into the pockets of developers and others who have no interest in the long-term viability and sustainability of the region. Ultimately, the residents and environment of the Intermountain West will pay the price for the short-sighted, willful ignorance of the water buffaloes.

  4. It’s not drought. It’s the management. (Milton Friedman said “Put the government in charge of the Sahara, and you’d have a shortage of sand in 10 years.”)

    They overallocated. Now then need to cut demand back to 9maf (or less, if you like Nature) and market the rest, via auction. Price rationing will be MUCH fairer than bureaucratic infighting. (Oh, and I don’t mind the auction $ going to the States in proportion to their CRC rights…)

    I’m here if anyone wants a solution. Don’t say that we didn’t see this trainwreck coming!

  5. Thank you for focusing on a point that is often lost on climate activists: “To the extent that politicians in Las Vegas or Phoenix or Los Angeles blame “drought” for the problems they face as Mead declines, they are misleading their constituents”.

    Global warming has become the do-all blame-all behind which all sorts of incompetent policies have learned to hide. That can’t be good for a proper handling of the phenomenon, and it is definitely deleterious as it just helps keeping alive what is evidently unsustainable.

  6. Maurizio –

    Thanks for joining the discussion. I don’t think you should misinterpret my analysis as suggesting that drought and climate change are unimportant factors in managing the basin. In that regard, I think Emily is correct.

    The situation I describe is a function of the arcane legal mechanisms that have split the lower from upper basin, and insulated the lower basin from the effect of drought. This very much occurs at the expense of Lake Powell and the upper basin. The upper basin is *very much* impacted by drought and climate change.

  7. I don’t know if I can add anything of value here.

    As David Zetland stated, “It’s not drought. It’s the management”.

    Right on. I wonder which level of government we should blame? Federal, State or Local? While we’re at it, let’s toss in the private sector and capitalism too.

    In the grand scheme of things, the Federal government oversees the distribution of the river to the states, tribes and Mexico. I also believe that they look at other ‘factors’ that influence the governance of the river (Endangered Species and other Federal laws). Once the water leaves the river (in distribution) other parties (other than the federal government), are responsible for the water.

    The State and more often – the Local levels of government are responsible for development and the ultimate usage of the water within its jurisdiction.

    Everyone loves growth. Better living conditions. Better jobs. Higher quality of living. All of these requiring higher demands on resources. Water included.

    Hard to blame the Federal government if the city of Las Vegas wants to expand and grants a local developer the right to build an additional thousand homes. Same should hold true for some farmer in Casa Grande or the Imperial Valley for wanting to plant more acreage. Development happens.

    Blame: I guess that we could start with the USGS. They estimated that the annual flow would be at 18.5 MAF. Looking at the latest estimates, they were a little high. I also guess that Reclamation should be blamed for developing the resource that been the life blood of the Southwest. Reisner really ripped Reclamation and MWD. I remember reading the book years ago. I admired the amount of research that went into his book. I also thought that he had very strong viewpoints based on conclusions that he understood. Reading his book, I got the distinct feeling that he felt the river had been exploited – not developed. I wonder how many other people walked away after reading his book and came to the same conclusions? It was very powerful writing and made some very strong statements. I ask myself, “Was it biased?”

    David says, “Adjust the price of water higher”. Problem solved! I don’t see it happening with gas prices. We are paying higher at the pump but still need the same amount to drive to work. I can’t see extending the same principle to water. People will riot over cutting the tap (Example: Klamath farmers).

    Root Causes: Over allocation. Using up the storage in the reservoirs faster than they can fill.

    Sure, we can blame the drought for this. We were headed to a water shortage due to over allocation and development. The drought just hastened the process a few years.

    John’s posts have focused on water management issues on the Colorado. From what I can read, it’s a complicated process. I just wonder what Marc Reisner’s take on this would be?


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