One of the hopeful notes coming out of the recent Colorado River discussions is the way the operation of Glen Canyon Dam in a more flexible way, to accommodate a broader range of values, is back on the table. The USBR alternatives released ahead of this week’s Colorado River Water Users Association, while requiring some tea leaf divination because of their brevity, seem to leave the door open for this discussion.

Jack Schmidt and I have a new white paper offering some assistance, based on our understanding of the legal and regulatory structure around Grand Canyon National Park and Glen Canyon National Recreation Area. The idea behind what we’re arguing isn’t to wag a regulatory finger and say, “The law requires us to do X.” Rather, we’re saying, “The law enables us to do X,” where for “X” we argue for the consideration of a wider range of social, cultural, and environmental values as we make decisions about how to divide the water up between Lake Mead and Lake Powell.

The resources in each part of this spectacular region are unique. Cataract Canyon was known to river runners as the “graveyard of the Colorado” because of its challenging rapids. Glen Canyon held sublime beauty amid the tranquility of its countless side canyons until they were inundated, and those side canyons are now reemerging. Grand Canyon is one of Earth’s greatest geological statements and is sacred to many native American tribes. In the eyes of the Bureau of Reclamation in the 1960s, and to millions of visitors today, Lake Powell is the “Jewel of the Colorado.” Lake Mead, visited by four million people each year, is the largest reservoir in the United States and allowed transformation of much of the American Southwest.

In 2025 we have an opportunity to establish policies for the Colorado River that honor these diverse and evolving environmental and societal values. The legal and administrative foundations that guide river and reservoir management in Cataract Canyon/Lake Powell/Glen Canyon/Grand Canyon/Lake Mead appear to encourage, and perhaps even require,
consideration of the many environmental and societal resources throughout this diverse region.

By Jack Schmidt | December 3, 2024

Drawdown of the Colorado River’s reservoirs now slightly exceeds the amount of gain that occurred during the 2024 snowmelt season. For the next four months until snowmelt begins again, the basin’s reservoirs will be drawing from the excess accumulated in 2023, demonstrating the immense challenge in balancing water consumption with supply.

In Detail…

On 30 November 2024, total basin reservoir storage was 27.5 million af (acre feet)¹, approximately two years’ supply at today’s rate of consumptive use and loss (Fig. 1). That amount is 43% of the maximum system contents of July 1983² and is the same amount as at the beginning of July 2021 when the basin’s water managers were beginning to get worried. Conditions are not quite as bleak as in summer 2021, because that year’s snowmelt season had already passed. Now, we can hope that the 2025 snowmelt season might be a good one. Nevertheless, reservoir storage is the bank account from which we draw to maintain the economy of the American Southwest and parts of northwestern Mexico. It would be preferable for there to be more water in that account.

Figure 1. Graph showing total storage in 46 reservoirs (blue line) in the Colorado River basin since 1 January 1999. Also shown are the total contents of Lake Mead and Lake Powell (orange line), total contents of Lake Mohave and Lake Havasu (red line), and 42 reservoirs upstream from Lake Powell (green line) which includes reservoirs managed by the federal and state governments, municipalities, and water districts.

Approximately 63% of current total reservoir storage is in Lake Mead and Lake Powell. Presently, there is approximately 400,000 af more water in Lake Powell than in Lake Mead, but the contents of Lake Powell are slowly being depleted. The contents of Lake Mead held fairly constant during the past month. The contents of Lake Powell decreased by approximately 4300 af/day during November, but the contents of Lake Mead decreased by only 800 af/day (Fig. 2). Upstream from Lake Powell, Colorado River Storage Project (CRSP) initial unit reservoirs, as well as Fontenelle Reservoir, decreased by only 600 af/day in November, and other Upper Basin reservoirs lost even less (400 af/day).

Figure 2. Graph showing total basin reservoir storage (blue line), and storage in different parts of the Colorado River watershed between 1 January 2021 and 30 November 2024.

Basin reservoir storage must be increased to improve the security of our water supply. We need to increase the balance in our “bank account,” and the only way to do that is to spend less than the amount of our actual water “income.” Most of our income arrives during the snowmelt season of late spring and early summer. Mid- and late-summer, fall, winter, and early spring is the period when we spend the snowmelt-season income, although summer rains and groundwater inflow offset some of our uses.

Occasionally, we have an unusually snowy winter, and the basin’s reservoirs significantly refill. 2023 was one of those years. Reclamation estimates that the natural flow of the Upper Basin³ was 17.4 million af in 2023, the third largest of the 21^st century (after 2011 and 2019), and total basin storage increased by 8.38 million af, only exceeded by the increase in storage in 2011⁴. 2024 was a moderately snowy winter.

2024 was a different story, however. The NRCS estimated that the peak snow water content in 2024 was 14% greater than the 30-year average, but dry soils and other effects of a warming climate limited natural flows to between 11.9 and 12.1 million af, which is less than the average for the 21^st century⁵. In 2024, the basin’s reservoirs increased in storage by 2.45 million af. The drawdown of the basin’s reservoirs as of 30 November was 2.46 million af, slightly more than the gain from snowmelt (Fig. 3). The contents of Lake Mead and Lake Powell increased by 1.39 million af in 2024, and the drawdown in those two reservoirs has been 1.07 million af this year. During the next four months, the basin will begin drawing from storage that accumulated in 2023.

Figure 3. Graph showing reservoir storage between 1 January 2023 and 30 November 2024, highlighting the amount of reservoir recovery during the past two snowmelt seasons and the amount of intervening reservoir drawdown. The drawdown of the basin’s reservoirs since July 2024 slightly exceeds the recovery that occurred due to snowmelt in 2024. 

Drawdown of the basin’s reservoirs has been much greater in 2024 than in 2023. The amount of drawdown between early summer and today is slightly more than the median drawdown for the past 15 years⁶ and is 43% greater than the drawdown at this time last year (Table 1). The drawdown of Lake Mead and Lake Powell in 2024 is slightly less than the median for the past 15 years⁷ but is 98% greater than it was at this time last year.

The total reservoir drawdown between early summer and 30 November is now 14% greater than in all of last year, and drawdown in Mead and Powell also exceeds the total drawdown in those reservoirs last year (Table 2).  We did well last year, but not so well this year.

There are many details ignored in this overview. Reservoir drawdown in the Upper Basin is not only determined by consumptive use, but also by reservoir operating rules that require winter drawdown and by requirements to provide environmental flows. Water use in southern California is significantly affected by water supply available from northern California, the Owens River, and locally. Nevertheless, every drop of water released from upstream is used, lost, or stored in a downstream reservoir, and total basin storage is the only available supply to make up the shortfall between annual precipitation and annual use.

Conservation in the Lower Basin and in Mexico is reducing drawdown in Lake Mead, and the storage contents of Lake Mead are likely to increase during the next few months as water is delivered from upstream. Drawdown of the total contents of Lake Mead and Lake Powell is still 0.32 million af less than what accumulated there from the 2024 inflow season and a 2024 deficit might not occur is Lower Basin water use is drastically reduced or if Upper Basin reservoirs are emptied.

Efforts to date to reduce water consumption in the basin have been significant, and required a significant investment by the federal government. Despite those efforts, we have four months ahead of us before snowmelt in 2025 begins, and we are likely to begin deficit spending unless radical changes in use are immediately implemented. The challenge faced by the federal government, Mexico, the seven basin states, every tribe, and every water user is immense and is not solely restricted to negotiating the post-2026 agreements. We remain in a water crisis today, and the time to greatly reduce water consumption is right now in the present moment.

• [1] Basin reservoir storage is for 46 reservoirs reported by the Bureau of Reclamation in its Hydrodata base https://www.usbr.gov/uc/water/hydrodata/reservoir_data/site_map.html.
• [2] There was 63.6 million af of storage in the basin on 15 July 1983. Some of this storage exceeded the generally accepted capacity of some reservoirs, notably Lake Powell.
• [3] at Lees Ferry
• [4] Basin reservoir storage increased by 8.78 million af in 2011.
• [5] Natural flows for calendar year and water year 2024 were 12.1 and 11.9 million af, respectively, based on Reclamation’s 12 September 2024 estimate. The average natural flow at Lees Ferry between 2000 and 2024 was 12.4 million af/yr, based on Reclamation’s estimates.
• [6] The median drawdown between the summer peak and 30 November during the past 15 years was 2.26 million af for the 46 reservoirs of the watershed.
• [7] The median drawdown between the summer peak and 30 November during the past 15 years was 1.16 million af for the total contents of Lake Mead and Lake Powell.
• [8]  Includes drawdown of Lake Mohave and Lake Havasu.

My colleagues with the Colorado River Research Group have a new policy brief out today taking another whack at the question of “assigned water” – water kinda sorta conserved, but left in storage so water agencies can pull it out again at some future date. Think “Intentionally Created Surplus” (ICS). At this point, nearly 40 percent of the water in Lake Mead is tagged as some agency’s private storage account, rather than being available for general system use.

By so effectively propping up reservoir elevations, Assigned Water delays or completely prevents the triggering of some mandatory shortage?based curtailments spelled out in the current rules…. [T]his approach has the unintended consequence of hiding the current paucity of shared (i.e., System) water available in Lake Mead, something that will ultimately become obvious when those waters are someday recalled.

This is the issue Arizona State’s Kathryn Sorensen (one of my CRRG colleagues) has been raising, and that Kathryn (with help from Sarah Porter and I) wrote about in October. The new CRRG paper argues that, as we move toward expanding the assigned water programs available to basin water users, we need to be mindful of the risks.

As near as I can tell from a lazy visit to the Wayback Machine, it was sometime around 2014 that I added the old Metropolitan Water District Colorado River Aqueduct map to my blog header. It’s a lovely map that has served me well these many years, but it doesn’t match my brand any more.

I was playing today with this 1823 map by Jose Narvaes (Narvaez?), but it didn’t pop the way I need a blog header image to pop. So I went instead with the 1938 USGS topo map of Albuquerque, which is gorgeous. Look at the loving detail of the Rio Grande as it makes the bend past “Old Albuquerque,” the Atrisco and Armijo ditches meandering down the South Valley, the swamps flanking the river.

I’m in the middle of some final choices about the art to include with the revisions to the manuscript of the new book Bob Berrens and I are writing – Ribbons of Green: The Rio Grande and the Making of a Modern American City, and I’ve been staring at both the Narvaes/Narvaez and the 1938 topo, trying to decide whether to include either. Narvaes/Narvaez I probably won’t. It’s lovely, but doesn’t move our narrative. The 1938 topo is on the bubble. It’s so damn pretty!

Finishing the Manuscript

I’ve been holed up for the last six weeks in a third floor garret (metaphor alert) doing the final revisions on the book, which is a full brain activity. I haven’t been paying much attention to the world around me, and I came down to the corner bodega (metaphor) to get some bread and cheese and ask the newsboy what’s been happening. He pointed me to Tony Davis’s story from the Tucson Star last week.* What the actual fuck, y’all? Is this the best you can do? I am so profoundly disappointed in Colorado River Basin leadership right now. Will I lose blog readership if I say “fuck” again?

The network is failing. Yeah, I’m talking to you. You are failing us. There are 40 million of us, and we have to figure out how to share this river.

Do better.

Another semester done

Luckily I’m not going to CRWUA this year. It’s early, conflicts with the last week of the UNM Water Resources Program class I’m co-teaching with Bob Berrens. It has once again been a joy to get to know a new cohort of the water managers of the future – a dozen joys, the years Bob and I have spent teaching the class together.

Spending the last three months teaching the class while I’m simultaneously deep in book revisions has been fun because of the interplay. Central to both is the idea that we have a multiplicity of values around water. Good water management does not mean pursuing my values. It means recognizing that there are many communities, and a multiplicity of values, and the institutions we have created to manage our way through that diversity, and whose evolution we are entrusted to steward, matter. I guess this has become my “meta-value.” I have my own personal values about the where and when and how of the use of water. But what is more important to me is that we have institutions that reflect the breadth of communities and values and interests other than mine.

* Sorry, I know it’s behind a paywall, but a) I appreciate the Star’s efforts to figure out a way to pay Tony to continue to do the important work of journalism, and b) the people I’m talking to here all have the pdf.

I put up a slide for my University of New Mexico water resources graduate students during class yesterday afternoon with two pictures – the emerging canyons at the upper end of Lake Powell, and a smallmouth bass.

When Lake Powell gets low, we get a) the remarkable emergence of Cataract Canyon, and b) warm water invasive smallmouth bass sneaking through Glen Canyon Dam’s outlets, headed downstream to dine on the endangered humpback chub. My University of New Mexico colleagues and collaborators Benjamin Jones and Bob Berrens famously dubbed these “green-vs-green” tradeoffs:

The Anthropocene epoch is characterized by extensive interactions among natural systems and managed human systems and institutional arrangements. Complex coupled human and natural systems, such as river systems with managed flows intended to produce a mix of community, ecosystem, energy, water and recreational services, will necessarily implicate multiple dimensions of societal value….

Managing for one – keeping Lake Powell high to keep smallmouth bass out of the Grand Canyon – inevitably conflicts with the other – keeping Lake Powell low to protect the emerging environmental values of Cataract Canyon.

In a new white paper out today, my colleagues Jack Schmidt, Eric Kuhn, and I argue for the creation of a process to better incorporate and manage the multiplicity of values along the Cataract Canyon/Lake Powell/Glen
Canyon/Grand Canyon/Lake Mead stretch of the Colorado River as we develop new post-2026 river operating guidelines. We recognize that keeping water flowing to taps and headgates across the Colorado River Basin is the primary motivation behind the new operating guidelines being developed by the Bureau of Reclamation. We argue that, as the community is writing those rules, we have an opportunity to incorporate a broader set of community values.

In particular, we argue that more creative water accounting methods would allow water to be either held upstream in Lake Powell for later delivery, or send downstream early to Lake Mead, in order to better take into account what Benjamin and Bob called the “multiple dimensions of societal value.”

The white paper elaborates on our formal proposal submitted in March to Reclamation as part of the agency’s Post-2026 decision process.