New Mexico’s Rio Grande is dwindling

2020: a year with no spring runoff on the Rio Grande

The Albuquerque Bernalillo County Water Utility Authority announced today that it will temporarily stop diverting water from the Rio Grande for our drinking water, shifting entirely to groundwater to meet municipal supplies through the summer. In itself, it’s no emergency for city water supplies – the groundwater is the reserve for use in dry years, when surface supplies are insufficient. But it’s a signal about how truly awful a year this is on the Rio Grande – we’ve done this sort of dry year shift to groundwater before, but as near as I can tell never this early in the year.

We are in the midst of what David Gensler, the water manager for the Middle Rio Grande Conservancy District, told the Albuquerque Journal’s Theresa Davis is “probably the worst we’ve experienced here in at least 45 years.”

The graph above tells the story – the black line is this year, amid an envelope of relative normalcy. We got no appreciable spring runoff peak. None.

Much of the water flowing through Albuquerque right now is water being released from previous years’ storage. Gensler’s Conservancy District will largely have run through that storage by mid-July. With a bunch of decisions yet to be made, including how water stored by the federal government for Native American communities will be doled out, it’s not clear when the bottom will drop out of that already meager flow. But know that it will drop out.

How low matters? It’s an arbitrary question, but for the graph below I chose 122 cubic feet per second, simply because it’s the cutoff point the Water Utility used to inform its decision to suspend diversions and switch to groundwater. How many days per year did the flow drop below 122 cfs?

Low flows in Albuquerque over the last half century. This is data from the Central Avenue bridge.


You can see that most years in the 1960s and 1970s saw many weeks of flows this low at the Central Avenue Bridge in Albuquerque, during a time when far more water was diverted from the river into the irrigation canals that flow through the valley – more water in the main canals, less in the river itself. Low flows in those days were far more common through Albuquerque than upstream of the big irrigation diversions.

Our management philosophy has changed since the 1980s, with a more efficient system of irrigation water delivery leaving far more water in the river itself. But this is an extraordinary year.

I’ll be watching closely to see how many days below 122 cfs we have this year.

Seeing Like a State: the corner of Ortega Road and Guadalupe Trail

Guadalupe Trail at Ortega Road in Albuquerque’s North Valley – here, it is a street

Some years ago, when I first began riding bikes in Albuquerque, my office chum Jimmie took me riding south through Albuquerque’s Rio Grande valley floor along a street called Guadalupe Trail. It’s not a street I would have found by myself – following the contours of one of the early acequias, the irrigation ditches that spiderweb across what was once the river’s flood plain, stopping and starting as it jogs around modern neighborhoods built where the valley’s farms used to be.

In his book Seeing Like a State, James Scott describes the Flemish city of Bruges in the 1500s:

The fact that the layout of the city, having developed without any overall design, lacks a consistent geometric logic does not mean that it was at all confusing to its inhabitants. One imagines that many of its cobbled streets were nothing more than surfaced footpaths traced by repeated use. For those who grew up in its various quarters, Bruges would have been perfectly familiar, perfectly legible. Its very alleys and lanes would have closely approximated the most common daily movements. For a stranger or trader arriving for the first time, however, the town was almost certainly confusing.

To borrow from Scott, then, Guadalupe Trail, following the contours of an old irrigation ditch, “could be said to privilege local knowledge over outside knowledge.”

When the modern Ortega Road was slapped down atop the old north valley maze – it’s not clear when, but old aerial photos show it was a dirt farm road by 1949 – it ran dead straight for its two-mile run across the valley floor. It is so legible to outsiders that the modern state has added speed humps to discourage automobile drivers from speeding.

It’s been ages since I’d ridden Guadalupe Trail, but in the Time of Pandemic, with a need for calm and a lot of miles in my legs, I’ve been following the contours of the old dirt ditchbanks. South of old Guadalupe Trail’s intersection with modern Ortega Road, it becomes what its name suggests – in the midst of a modern city, an old dirt trail.

Why I hate “Drought Contingency Plan” (the name, not the plan)

“We really need to call [what we’re experiencing] aridification — the drying out of the Colorado River Basin because of climate change, we can’t just call it ‘drought’ anymore,” Fleck said. “It appears to be this permanent phenomenon that’s lowering the lake levels. You should not expect it to return to high lake levels over long periods of time. That’s just not something we can expect to happen.”

Via Lexi Peery, KUER

Tradeoffs: Colorado River water, flowing down the Rio Grande

Imported Colorado River water flows down the Rio Grande. Albuquerque, New Mexico, June 19, 2020

Faced with the challenge of teaching some or all of our coursework this fall on line, my University of New Mexico Water Resources Program colleagues and I have been having a think about what we’re trying to accomplish.

A lot of the thinking revolves around translating our educational goals from face-to-face classroom discussion to the new “modalities”, as the current edu-speak puts it. But it’s a useful moment, as I head into my eighth fall teaching , and my fifth as the program’s director, to also have a think about the underlying goals.


As is my way – always, but more so in the Time of Pandemic* – I had occasion to stop on Friday’s bike ride to look at the Rio Grande south of the Albuquerque’s old Route 66 bridge.

The flow’s been hovering around 500 cubic feet per second, which is low for this time of year. It is what we’ve come to call an “institutional hydrograph”.

2020 runoff on the Rio Grande – a year with no spring pulse

The hydrograph is a familiar graph to folks in water management (or studying it!) – time along the x axis, flow on the y axis. The graph above is an example of my attempt to place the current year (the black line) into historic context. We’ve had a gauge at the Central Avenue Bridge since the mid-1960s, and you can see the “normal” pattern: low flows through the winter, then more water in spring as the mountain snows melt.

This year, not so much.

A look at the gauges upstream tells the story: almost no natural flows coming into the valley from either the Rio Chama or the main stem of the Rio Grande. Almost all of the water flowing into the valley right now is coming from storage in El Vado and Abiquiu reservoirs, and a big chunk of that is Colorado River water, imported via the San Juan-Chama Project.

We call it an “institutional” hydrograph because of the role of water management institutions in shaping it. We write rules, create government agencies to implement those rules, and through those government agencies build physical plumbing to move water. The rules both create the plumbing, and create the decision-making framework for determining how much water moves through it.

The rules are how we mediate the tradeoffs.

In this case, the set of rules that determine flows in the Colorado River – the 1922 Compact, the Upper Basin Compact, the Colorado River Storage Project Act – both enabled construction of the San Juan-Chama Project and determined how much water we would move through it. The water is then handed off to more rules that govern Rio Grande water allocation and delivery, along with the plumbing that brings some of that imported Colorado River water to my home and garden.

And, in the process, keep some water flowing past the Central Avenue Bridge.


* I checked my Strava maps – three bike rides to the river last week, eight total crossings. It has to be an even number or I’d never get home.

March 1985: when everything on the Colorado River changed

Brett Walton had a great bit of business in yesterday’s Circle of Blue story on 2019’s remarkable drop in Colorado River Lower Basin water use:

The last time water consumption from the river was that low was in 1986, the year after an enormous canal in Arizona opened that allowed the state to lay claim to its full Colorado River entitlement.

Which led, over on the twitter, to a discussion involving the LA Times’ Sammy Roth and others about how people were talking, and thinking, about the milestone back in 1985 when the Central Arizona Project first switched on.

As we were working on our book Science Be Dammed, Eric Kuhn and I often turned to newspapers of the day to see what people were saying publicly about the events we were studying, as they were happening. For the 1985 milestone, we turned to the LA Times’ Bill Boyarsky. From Chapter 18 of the book:

With hindsight, it is possible to date the beginning of the twenty-first-century changes on the Colorado River to March of 1985, when Arizona pumped the first water from Lake Havasu into the Central Arizona Project canal. “Now as a trickle but soon as a torrent,” Bill Boyarsky wrote from Phoenix in the Los Angeles Times, “Arizona is finally taking its share of the Colorado River, and the impact will be felt from here to the Pacific beaches.” Boyarsky’s warning was explicit—the surplus water that until then had flowed west to Southern California would now be headed east, toward the Phoenix metro area, which was growing at a rate of more than 75,000 people a year.

In 1985, California took 4.8 million acre feet of main stem water from the Colorado. In 2019, it took 3.9 million acre feet.

The roots of a coming Lake Powell Pipeline legal tangle

By Eric Kuhn

Location of Lower Colorado River Basin community of St. George, Utah

As Utah pushes forward with its proposed Lake Powell Pipeline – an attempt move over 80,000 acre feet per year of its Upper Colorado River Basin allocation to communities in the Lower Basin – it is worth revisiting one of the critical legal milestones in the evolution of what we have come to call “the Law of the River.”

The division of the great river’s watershed into an “Upper Basin” and “Lower Basin”, with separate water allocations to each, was the masterstroke that allowed the successful completion of the Colorado River Compact in 1922. But the details of how that separation plays out in water management today were not solidified until a little-discussed U.S. Supreme Court ruling in 1955, in the early years of the decade-long legal struggle known as “Arizona v. California.”

Most, if not all, of the small army of lawyers, engineers, water managers, board members, academics, tribal officials, NGO representatives, and journalists now actively engaged in Colorado River issues are familiar with the 1963 Arizona v. California Supreme Court decision. It was Arizona’s great legal victory over California that cleared the road for the Congressional authorization and construction of the Central Arizona Project (CAP).  Many in the ranks are also quite familiar with Simon H. Rifkind, the court-appointed Special Master who conducted lengthy hearings and worked his way through a mountain of case briefs and exhibits before writing his 1960 master’s report that set the stage for the court’s decision. Few of us, however, are familiar with George I. Haight. Haight was the first special master in the case, appointed on June 1st, 1954.  He died unexpectedly in late July 1955.  Two weeks before his death he made a critical decision that was upheld by the Supreme Court and set the basic direction of the case. Today, as the basin grapples with climate change, shortages, declining reservoir levels, and most recently, Utah’s quest to build the Lake Powell Pipeline exporting a portion of its Upper Basin water to the Lower Basin to meet future needs in the St. George area, Haight’s forgotten opinion looms large.

In late 1952 when Arizona filed the case, it was about disputed issues over the interpretation of both the Colorado River Compact and the Boulder Canyon Project Act. Among its claims for relief, Arizona asked the court to find that it was entitled to 3.8 million acre-feet under Articles III(a) & (b) of the compact (less a small amount for Lower Basin uses by New Mexico in the Gila River and Utah in the Virgin River drainages), that under the Boulder Canyon Project Act California was strictly limited to 4.4 million acre-feet per year, that its “stream depletion” theory of measuring compact apportionments be approved, and that evaporation off Lake Mead be assigned to each Lower Division state in proportion to their benefits from Lake Mead.  California, of course, vigorously opposed Arizona’s claims.  One of California’s first moves was to file a motion with Haight to bring into the case as “indispensable” parties the Upper Division states; Colorado, New Mexico, Utah, and Wyoming. California’s logic was that the compact issues raised by Arizona impacted both basins and every basin state (history has shown California was right on).

The Upper Division states were desperately opposed to participating in the case.  Backing the clock up to the early 1950s, these states, including Arizona, had successfully negotiated, ratified, and obtained Congressional approval for the Upper Colorado River Basin Compact. They were now actively seeking Congressional legislation for the Colorado River Storage Project Act (CRSPA), the federal law that would authorize Glen Canyon Dam (Lake Powell) and numerous other Upper Basin projects.  Upper Basin officials feared that if they became actively involved in Arizona v. California, California’s powerful Congressional delegation would use it as an excuse to delay approval of CRSPA (as it had successfully done with the CAP). Thus, these states and their close ally, Arizona, opposed California’s motion.

The basis of their opposition was relatively simple; Under the compact, except for the Upper Basin’s obligations at Lee Ferry, the basins were separate hydrologic entities, the issues raised by Arizona were solely Lower Basin matters, and that Arizona was asking for nothing from the Upper Division states.  Their strategy worked. In a July 11, 1955 opinion, Haight recommended California’s motion be denied. By a 5-3 decision, the Supreme Court upheld his recommendation and, except for Utah and New Mexico as to their Lower Basin interests only, the Upper Division states were out of the case.  The Upper Division states cheered the decision.  Arizona’s crafty Mark Wilmer devised a new litigation strategy built on Haight’s logic and ultimately Haight’s successor, Simon Rifkind, ruled that there was no need to decide any issue related to the compact. For more details, see Science Be Dammed, Chapter 15.

In convincing Special Master Haight to deny California’s motion, Arizona and the Upper Division states turned him into an ardent fan of the Colorado River Compact. Haight opined “The compact followed years of controversy between the states involved. It was an act seemingly based on thorough knowledge by the negotiators. It must have been difficult of accomplishment. It was the product of real statesmanship.” In justifying his decision, he found “The Colorado River Compact evidences far seeing practical statesmanship. The division of the Colorado River System waters into Upper and Lower Basins was, and is, one of its most important features. It left to each Basin the solution to that Basin’s problems and did not tie to either Basin the intra-basin problems of the other.”  A few pages later, he says “The Compact, by its terms, provides two separate groups in the Colorado River Basin. Each of these is independent in its sphere. The members of each group make the determinations respecting that group’s problems,”  and finally “because by Article III of the Colorado River Compact there was apportioned to each basin a given amount of water, and it is impossible for the Upper Basin States to have any interest in water allocated to the Lower Basin States.”

Fifty five years later, how would Special Master Haight view the problems the Colorado River Basin is facing where climate change is impacting the water available to both basins, through the coordinated operation of Lakes Mead and Powell the basin’s drought contingency plans are interconnected, critical environmental resources in the Grand Canyon, located in the Lower Basin, are impacted by the Upper Basin’s Glen Canyon Dam, and most recently two states, New Mexico and Utah, have found it desirable to use a portion of each’s Upper Basin water in the Lower Basin?  With one major exception, I think he would be pleased. Haight understood that through Article VI, the compact parties had a path to resolve their disputes and implement creative solutions. The first part of Article VI sets forth a formal approach where each state governor appoints a commissioner, the commissioners meet and negotiate a solution to the issue at hand and then take the solution back to their states for legislative ratification. This formal process has never been used, but luckily, Article VI also provides an alternative. The last sentence states “nothing herein contained shall prevent the adjustment of any such claim or controversy by any present method or by direct future legislative action of the interested states.”  After Arizona refused to ratify the compact in the 1920s Colorado’s Delph Carpenter successfully used federal legislation to implement a six-state ratification strategy (the Boulder Canyon Project Act).

The exception that would concern Haight is Utah’s unilateral decision to transfer about 80,000 acre-feet of its Upper Basin water to the Lower Basin via the Lake Powell Pipeline. The LPP violates the basic rationale that Haight used to keep the Upper Basin out of Arizona v. California and for which Utah and its sister Upper Division states fought so hard.  The project uses water apportioned for exclusive use in the Upper Basin, terms carefully defined by the compact negotiators, to solve a water supply problem in the Lower Basin.

Defenders of Utah’s may believe a precedent has already been set– the Navajo-Gallup Pipeline, which delivers 7,500 acre-feet of New Mexico’s Upper Basin water to the community of Gallup and areas of the eastern Navajo Nation. But if that is to be cited as a precedent, it comes with an important caveat. New Mexico addressed the compact issues through federal legislation with the participation and consent of the other basin states and stakeholders. Utah, by comparison, apparently believes federal legislation, and by implication the consent of others in the basin, is not needed.

In the face of climate change induced declining river flows and increased competition for the river’s water, there is no question that the basic compact ground rules devised by the negotiators a century ago will face increasing pressure.  There will likely be more future projects and decisions that, like the LPP, will challenge the strict language of the compact. The question now facing the basin is how will this revisiting be accomplished? Will it be done in an open and transparent manner that engages not just the states, but a broad range of stakeholders and implemented through legislation (not easy in today’s world, as a practical matter it requires no opposition from any major party to get through the Senate) or by a series of unilateral decisions designed to benefit or advantage individual states or specific entities, but with no input or buy-in from the basin as a whole?

Coping with Megadrought in the Colorado River Basin

My NIDIS webinar from earlier this week is posted.

Key bits:

  • This year’s “sneaky drought” is a problem.
  • The longer term “megadrought” (climate change-driven aridification) we seem to be in is an even bigger problem.
  • We’ve done some great work in the Colorado River Basin reducing our use of water and building the institutional widgets to cope with scarcity.
  • We have more work to do.

The Birth of the Cool

Santana, Tanglewood, August 1970.

Carlos Santana was born in Jalisco, the son of a mariachi, and grew up in that stateless borderland between Tijuana and San Francisco playing first the violin, then the guitar. There was a breadth to his musical education:

If I would go to some cat’s room, he’d be listening to Sly and Jimi Hendrix; another guy to the Stones and the Beatles. Another guy’d be listening to Tito Puente and Mongo Santamaría. Another guy’d be listening to Miles and Coltrane. To me, it was like being at a university. (source)

There’s an intoxicating moment about 3:30 into this this video of a live performance of Soul Sacrifice at Tanglewood in the summer of 1970.

He’s finished with the opening solo, and wanders off as he hands the song over to the band’s drummers and bass player (a joyous propulsion that is one of the reasons this is one of my favorite versions of one of my favorite songs).

Then he returns, a cigarette hanging from his mouth, now without his guitar, and finds a cowbell to join the rhythm section.

He had just turned 23.

Google Maps said there’s a uranium mine out here. Also, a Wendy’s.

Mount Taylor in the distance, the Rio Puerco Valley in the foreground. Note growing number of water bottles on the bike frame.

In the Time of Pandemic, the ability to refill my water bottles has become an unexpected bike riding constraint. Worst case, if I couldn’t find a drinking fountain, I used to pop into a Kwik-E-Mart and buy a bottle. So, yeah, pandemic, amiright?

I hate those water pack things, and the discomfort of throwing extra bottles in those goofy back pockets on my cycle shirts. So I spent a bit of the afternoon yesterday (which was, I note for the record, a Saturday, if you’re losing track) installing a new bracket on my bike frame so I can carry more bottles.

Thus it was this morning that, with a half gallon of water strapped to my frame and pockets overfilled with Lissa’s ferociously potent oatmeal cookies, I found myself on Shooting Range Road on Albuquerque’s farthest western fringe. The mesas on Albuquerque’s west side take two steps down to the river, and the uppermost bench is largely devoid of human habitation, save the old Double Eagle Airport, the “Compost del Rio Grande” where Albuquerque spreads its sewage solids out to dry (“rich in organic matter, nitrogen and trace minerals“), the city’s emergency winter shelter for people experiencing homelessness, and the shooting ranges.

Mostly its just wonderfully scraggly desert. Even when there isn’t a pandemic, it’s got no Kwik-E-Marts, so I’d never ridden out Shooting Range Road. But now I have cookies and a half gallon of water!

the fading dreams of Paseo del Volcan

Years ago, when I was young and racy, we used to ride out what was then called Paseo del Volcan (because it circles Albuquerque’s west side volcanoes). A few years back, they renamed it “Atrisco Vista” and planned a new “Paseo del Volcan”, a loop rode west of Albuquerque, studded with new housing developments and economic opportunity.

This was a fading idea before the 2008 economic shitstorm, and never unfaded in the years that followed. But lordy we’ve got some nice powerpoints and promotional graphics – “connectivity, access, economic growth“.

Here Lies Shorty

In the meantime, it’s a great place for Albuquerque to spread its shit to dry, and shoot. I found myself late this morning at the old Wild West action shooting range, complete with old timey cemetery up the hill from the shooting range – closed, sadly, because of the pandemic.

One of the fun things about these long rides along the vast open upper mesa is exploring Google maps quirks. Last month it was the Mystique Food Truck, and today’s outing included a uranium mine and a Wendy’s, out in the middle of the empty. I cannot tell you for sure that there is no uranium mine next to the drying sewage solids (it might be underground, yes?) but there for sure was no Wendy’s here – unless it’s underground too?

no Wendy’s there

For much of the first months of the pandemic, my mental quirk had been to stare at the cupboards and worry about running out of food. With our offspring handling the grocery shopping for their elders, this really hasn’t been much of a worry of late, so the quirk has transferred to worrying about running out of water on a long bike ride. Two-plus months in, the bike rides are getting a good deal longer, and the weather a good deal warmer.

So I spend hours on line pondering mounting brackets to carry extra bottles, and hunt for the largest bottles. By the time this project is over, I’ll be able to carry a gallon!

There are whole new areas of Albuquerque’s far west side to explore, with nary a Kwik-E-Mart or Wendy’s in sight. The only constraint now will be how many oatmeal cookies I can carry.


2020 Is a Dry Year on the Colorado River. What Happens Next Year Will Be More Important

By Eric Kuhn

This winter’s decent snowfall has turned into an abysmal runoff on the Colorado River, thanks to the dry soils heading into the winter, along with a warm spring. It’s alarming, but given the large amount of storage capacity in the basin and the recent string of good runoff years in the upper Basin, with five of the last six years close to average or better, most of the basin’s water users will not face significant problems this year. Our bigger concern is what happens next year.  Are we headed for a multi-year drought?

Watching the bottom drop out

As of the third week of May, the Colorado Basin River Forecast’s Center’s (CBRFC) daily model is closely tracking the minimum probable forecast inflow to Lake Powell used by the Bureau of Reclamation to prepare its April 2020 24-month study. The 24-month studies are an important decision-making tool under the 2007 Interim Guidelines, which govern the river’s operation.  The 24-month studies show projected monthly reservoir inflows, storage elevations, water deliveries, power generation, and other system data for the next two years. They support critical operational decisions under the Interim Guidelines and associated drought contingency plans, including annual releases from Glen Canyon Dam and shortage levels for Lake Mead water contractors.

declining Colorado River forecast, courtesy CBRFC

Reclamation’s monthly 24-month studies for January – July are based on the CBRFC’s most probable unregulated April-July inflow forecast for Lake Powell and other key Upper Basin reservoirs.  Approximately quarterly Reclamation also publishes 24-month studies based on high flow and low flow scenarios for the remainder of the runoff year – a one-in-ten chance “worst case” and a one-in-ten chance “best case.” This April’s 24 month studies were based on a most probable April – July inflow to Lake Powell of 5.6 million acre-feet, a minimum probable inflow of 4.1 million acre-feet, and a maximum probable inflow of 8.1 million acre-feet.  The CBRFC daily model runs now show about 4 million acre-feet, worse than the April minimum probable forecast. For Water Year 2020 (all 12 months not just April- July), the total unregulated inflow to Powell is projected to be 6.7 million acre-feet, about 60% of average, a little more than half of WY 2019’s 13 million acre-feet, but better than the 2018 drought year of which had an unregulated inflow of 5.5 million acre-feet.

Little impact this year, the potential for big impacts in the future

What does this dry 2020 year mean for the operation of the Colorado River basin, specifically, Lakes Powell and Mead?  Based on the 24-month studies, the answer is not much.  The 2020 operations are already fixed. Glen Canyon Dam will release 8.23 million acre-feet and Lake Mead users will be in a “Tier Zero” shortage under the DCP, requiring a small amount of conservation. Even before the official “Tier Zero” declaration, Lower Basin users were voluntarily saving more than the cuts required under the DCP.  And, even if this year’s runoff continues to decline, it is very unlikely to change next year’s projected annual release of 9.0 million acre-feet from Glen Canyon Dam. Based on the April minimum forecast, at the end of calendar year 2020 Lake Powell is projected to be about 20’ higher than the 3575’ elevation trigger that would result in a reduction of Glen canyon releases to 7.48 million acre-feet in WY 2021.  20’ of elevation in lake Powell at current levels is almost two million acre-feet of storage.  It’s very unlikely that the forecast will lose or be off by that much water.

This good news is the result of last year’s big winter which gave us an above average runoff, charging Lake Powell and the other Upper Basin Reservoirs. The real concern for the basin is not 2020, but 2021 and beyond – will 2020 be the first year of a multi-year drought period?  The last significant multi-year drought in the Colorado River basin was 2012-2013. The second year of a multi-year drought tends to have greater impacts than the first, as water managers try to refill upstream reservoirs, amplifying the multi-year drought impacts on Lake Powell. If 2021 is again dry (below about 70% of average), the storage elevation of Lake Powell could easily drop below elevation 3575’ reducing the annual Glen Canyon Dam release in WY 2022 to 7.48 million acre-feet, pushing Lake Mead into a Tier One shortage. A three-year drought or longer would quickly push Lake Mead downward requiring the large shortages anticipated by the Interim Guidelines and Lower Basin DCP.

Multi-year droughts

Looking at the Bureau of Reclamation’s natural flow data base (NFDB, Jan 2020 version, 1906-2018), two-year droughts are relatively common, three years and longer, less so.  The driest two through four-year periods are shown below:

Two-year periods average annual flow
2002-03 8.163 MAF/year
1976-77 8.318 MAF/year
2001-02 8.447 MAF/year
2012-13 8.708 MAF/year
Three-year periods
2002-04 8.589 MAF/year
2001-03 9.116 MAF/year
2000-02 9.145 MAF/year
1954-56 9.878 MAF/year
Four-year periods
2001-04 9.198 MAF/year
2000-03 9.472 MAF/year
1953-56 10.197 MAF/year
1989-92 10.487 MAF/year

As one can see, many of the driest multi-year periods are associated with the 2000-2004 drought period, which is by far the driest five-year period.  What should concern us is the threat of anthropogenic aridification making multi-year droughts more common.  Three of the four driest two-year and three-year periods as well as the driest four and five-year periods have all happened in the last 20 years, which, not coincidentally happens to include almost all of the warmest years the basin ever recorded in the basin.

Implications for future river management

Being better prepared for future multi-year droughts will be one of the challenges facing the basin stakeholders as they begin to consider the post-2026 river. For example, even though Water Year 2020 has turned surprisingly dry and the basin is under an escalating threat of multi-year droughts, the only parameters used to determine the annual release from Glen Canyon Dam are the projected elevations of Lake Mead and Powell from the 24-month studies. Therefore, the annual release from Glen Canyon Dam for Water Year 2021 will be 9.0 million acre-feet, 750,000 acre-feet more than the normal minimum requirement, putting the Upper Basin under additional risk if next year and beyond are dry. Parameters such as recent trends of naturalized stream flows and regional temperatures, longer-term forecasts, and the consensus messages from climate science are not currently considered.

For the river’s post-2026 operational guidelines, let’s hope that changes.