Strongly worded letter today from John Entsminger of the Southern Nevada Water Authority about the failure to reach a deal on Colorado River cutbacks:

More later, I’m supposed to be paying attention to a zoom meeting, but making this as broadly publicly available as possible seemed important. Click the “view document” link to see the whole thing.

By Jack Schmidt, John Fleck, and Eric Kuhn

On the eve of the release of the US Bureau of Reclamation’s August Colorado River reservoir forecasts – freighted with meaning this month because of Reclamation’s ultimatum to the states about the need to cut water use – we look back at the last four decades of water-supply management to pose the central question:

How did we get into this mess? Our answer in brief:

When the Colorado’s flow was up, we used it all.

When it was down, we drained the reservoirs.

The river’s natural flows have been down for a long time.

And during the few stretches of somewhat higher flows, we did not significantly refill the reservoirs.

A failure to set water aside for the future

Colorado River water use outpacing supply. Graph by Jack Schmidt, Utah State University

Operating year to year, it is easy to get lost in the river’s annual ups and downs, and the immediate desire to get water to farm fields and cities – THIS YEAR! NOW!

But the longer view, based on the best available data, makes clear our mistakes during the past 20 years. Since the year 2000, the blue line in the graph above has spent little or no time above the red line. That is water use outpacing supply.

The result – the most recent three consecutive dry years have left us with headline-clear problems:

• Reservoir storage is 66 percent less than it was in 2000.
• Reclamation is concerned about the structural integrity of the river outlets at Glen Canyon Dam that will be continuously needed if Lake Powell falls below the minimum power pool elevation.
• Las Vegas’s old water supply intakes – and dead bodies! – are emerging from the Lake Mead mud.

21st century Colorado River water use has exceeded supply by 1.2 million acre feet per year

The graph’s nuances are worth noting.

Blue dots represent each year’s total natural water supply – the sum of the natural water yield of the entire Upper Basin and of the many springs and tributaries that flow into the Colorado River in the Grand Canyon. This natural supply, not considering the Gila, Bill Williams, or Virgin Rivers, averaged 12.8 maf/yr (million acre feet per year) in the 21^st century, 23% less than the average between 1981 and 1999.

To help visualize longer-term trends and cycles, we statistically smoothed the data to create the blue line, which more clearly shows the longer-term ups and downs of the Colorado River’s flow. The smooth line makes clear the wet periods of the 1980s and 1990s, and the deep droughts of the early 2000s and of today. Importantly for our current mess – the “wets” of the 21^st century were not as wet, and the “drys” were drier, than those of the late 20^th century.

The red line – total basin water use and reservoir evaporation loss (not including uses and losses in the Gila, Bill Williams, Virgin, or Little Colorado watersheds)  – crept up through 2000 as the Central Arizona Project finally grew into the paper water allocations of the 20^th century Law of the River.

Total consumptive uses and losses, including treaty deliveries to Mexico, peaked in 2000 at ~15.8 maf and were reduced during the next 2 years. Thereafter, average basin-wide consumptive uses and losses remained ~14.2 maf/yr between 2003 and 2020, and individual years were consistently within 4% of the average of that period. Throughout the 21^st century, total Upper Basin uses and losses were ~30% of the basin-wide total.

Sustained consumptive uses and losses that exceed the natural supply can only be sustained by draining the reservoirs – but only so long as there is available water in the reservoirs. Thus, it is no surprise that the 21-year average (2000-2020) rate of water consumption and losses that exceeded the natural supply by ~1.2 maf/yr led to today’s crisis.

There were a few opportunities to rebuild reservoir storage, especially in 2005, 2008, 2009, 2011, 2017, and 2019, but a decades’ long water consumption rate that exceeds natural supply is unsustainable. The reservoirs are now mostly drained.

The failure to refill

The reservoirs’ decline. Graph by Jack Schmidt, Utah State University

The history of water storage, described in the two graphs, has gone like this:

• The reservoirs were brim full in the mid-1980s and lots of water passed through the delta to the Gulf of California
• Reservoirs were somewhat depleted in the late 1980s and early 1990s when basin-wide consumption exceeded natural supply, but the reservoirs refilled in the late 1990s due to three years when supply greatly exceeded consumption (1993, 1995, and 1997). Thus, the reservoirs were relatively full in 2000 when the Millennium Drought began.
• Reservoir storage greatly decreased thereafter when the natural supply was never greater than 11.7 maf/yr (2001) and was as low as 6.39 maf/yr (2002).
• Reservoir storage stabilized at a new lower level thereafter when there were a few wetter years between 2006 and 2011. The last relatively wet year was 2019, but our continued use of large quantities of water was such that this sequence of somewhat wetter years was not used to rebuild reservoir storage.
• Natural supply has been especially low between 2020 to 2022, averaging 9.4 maf/yr, which is far less than the basin-wide consumptive uses and losses that are approximately 14 maf/yr (we note that basin-wide consumptive use data are not available for 2021.)

Thus, today’s crisis – two decades of low natural supply, including some short, very dry periods, cannot sustain consumption and losses that exceed the natural supply and that have not significantly changed since 2003.

Policy Implications

What are the policy implications of this analysis?

• There has been a natural cyclicity of somewhat wetter and somewhat drier years, but the recent wet periods, when the reservoirs might have been refilled, have not been as wet as in the 1980s and 1990s.
• The recent dry period that we are experiencing today since 2020 is comparable to the dry period of 2000-2005.
• Reductions in consumptive water use and losses mandated by Commissioner Touton will need to remain in place through the end of the present very dry cycle and well into any future wetter cycle in order to rebuild reservoir storage.
• The call for an immediate reduction of 2-4 maf/yr in consumptive uses and losses is an unprecedented reduction in relation to the pattern of use in the watershed since 2003.
• Anything less than sustained reductions of the scale demanded by Touton’s ultimatum risks crashing the system – certainly if we get another year or two of very low runoff from the Rocky Mountains.

An explanation of our methodology

The present water-supply crisis is a simple mass balance problem and we sought to describe this mass balance in the simplest way – averaging for the entire watershed

How did we consider inflows?

• We used Reclamation’s estimates of natural flow at Lees Ferry, including the provisional data that are available for 2022. We used ~40 years of data.
• We estimated inflows downstream from Lees Ferry that flow into Lake Mead based on the difference between USGS measurements made at Lees Ferry at the upstream end of the Grand Canyon and near Peach Springs, just upstream from Diamond Creek at the downstream end of the Grand Canyon. These data are available for 1990-2021, and we used the average for the 1990s as the estimated inflows of the 1980s. We used the average for the 2010s as the inflow in 2022. These data include inflows from the Paria and Little Colorado Rivers.
• We added these two data sets as the available natural supply available for water users. We did not consider the natural inflow of the Virgin, Bill Williams, or Gila River because these rivers, with only rare exceptions like year 2005, are fully depleted and considered the sole domain for use by the Lower Basin states. Note that 2001-2005, Lower Basin use of these three tributaries was 2.2 maf/yr (the last years for which these data are available).

How did we estimate consumptive uses and losses?

• We used Reclamation’s Consumptive Uses and Losses reports and Water Accounting reports
  • For the Upper Basin, we used revised and peer reviewed data prior to 1995 and provisional data 1996 to 2020. Data for 2021 are not available.
  • For the Lower Basin, we used Colorado River system summaries prior to 2005.
  • For the Lower Basin, we used Water Accounting reports 2006-2021.
  • We assumed that Lower Basin mainstem reservoir evaporation 2006-present was same as the average for 2001-2005 (1.1 maf/yr).
  • We only considered Treaty deliveries to Mexico as a use, and large surplus flows of the 1980s and 1990s were assumed to have passed to the sea.

We assumed that the uncertainty of all values was 2 or 3 significant digits and rounded off our calculations accordingly.

the authors

• Jack Schmidt is Janet Quinney Lawson Chair in Colorado River Studies, Center for Colorado River Studies, Watershed Sciences Department, Utah State University
• John Fleck is Writer in Residence at the Utton Transboundary Resources Center, University of New Mexico School of Law; Professor of Practice in Water Policy and Governance in UNM’s Department of Economics; and former director of UNM’s Water Resources Program.
• Eric Kuhn is retired general manager of the Colorado River Water Conservation District based in Glenwood Springs, Colorado, and spent 37 years on the Engineering Committee of the Upper Colorado River Commission. Kuhn is the co-author, with Fleck, of the book Science Be Dammed: How Ignoring Inconvenient Science Drained the Colorado River.

Janet Wilson had a helpful story yesterday in the Desert Sun about California’s negotiations over its piece of the looming Colorado River cutbacks. Its bottom line is that California – the state with the largest Colorado River allocation – is talking about kicking in 500,000 acre feet of water. Or maybe it’s really just 400,000 acre feet of water – as the Metropolitan Water District of Southern California’s Bill Hasencamp told her, paraphrased, the negotiations are fluid and numbers could change.

A reminder of what Reclamation Commissioner Camille Touton told senators just seven weeks ago:

In the Colorado River Basin more conservation and demand management are needed in addition to the actions already underway. Between 2 and 4 million acre feet of additional conservation is needed just to protect critical elevations in 2023. (emphasis added)

4 million acre feet is obviously out of reach. It always was.

But if Wilson’s numbers about California’s contributions are right – and she’s a good reporter, we have every reason to believe they’re in the ballpark – 2 million acre feet of additional conservation is beyond the grasp of a voluntary deal as well.

The arithmetic is straightforward.

The Upper Basin has said “not our problem“.

Nevada’s share of the river is so tiny that its contribution is couch cushion change, a rounding error.

That leaves, in round numbers, 1.5 million acre feet of water to come out of Arizona just to get to Touton’s bottom line number for additional conservation. That would require completely drying up the Central Arizona Project canal. (CAP is taking 1.031maf this year, and averaged ~1.4maf over the previous fives years). I’m frequently surprised by Arizona, but it seems unlikely that they’ll agree to a voluntary deal that dries up the CAP canal. If that’s where we end up, Arizona’s best alternative to a negotiated agreement will be to just make the feds do it, make them take the heat. (Worth noting that FiveThirtyEight has Arizona Democrat Mark Kelly slightly favored to hold his seat. Water politics is high stakes politics.)

Combine that with the reality that Arizona’s Native American communities, major water rights holders, have complained that they’ve been cut out of this entire process, according to a July 22 letter just surfaced.

I can imagine creative accounting that might allow everyone to grin through their teeth and count water moved down to Lake Powell from Flaming Gorge and other Upper Basin reservoirs as part of the 2 million. That’s pretty clearly not what Touton called for in June. It’s not “additional conservation”. But it might create some space for a face-saving deal.

Whether that would be enough to protect us from dead pool is another question.

A reminder of the stakes

The Bureau of Reclamation’s most recent “minimum probable” model runs show Lake Powell dropping below power pool – unable to generate electricity, and forced to move water through bypass tubes that Reclamation has made clear it does not trust – by October 2023.

Under that same scenario, Lake Mead drops to elevation 992 feet above sea level over the next 24 months.

(Trust me, having to type a Lake Mead elevation level without having to use a comma made me clench.)

At that point, a lack of water will make massive cuts a self-executing reality. We’ve drained our buffer. You can’t use water that doesn’t exist.

In a July 22 letter, the leaders of 14 Colorado River Basin Tribal governments complained to the U.S. Department of Interior about being left out – again – of the current negotiations around short terms Colorado River cutbacks:

Click through to see the full letter.

Duly noted

Sadly for most of you, this story is behind Politico/E&E paywall.

By John Fleck, Eric Kuhn, and Jack Schmidt

As stakeholders negotiate the current crisis on the Colorado River, we believe the representatives of the states of the Upper Basin – our states – are making a dangerous argument.

Their premise is simple. With deep cutbacks needed, the Upper Basin states argue that their part of the watershed already routinely suffers water supply shortages in dry years. Without the luxury of large reservoir storage along the rim of the watershed that might store excess runoff in wet years and supplement supplies in dry years, the argument goes, the Upper Basin is limited by the actual mountain snowpack in any given year.

This is certainly true in many places. One of us (Fleck) lives in a community (Albuquerque, New Mexico) that has routinely seen supplies of trans-basin San Juan-Chama Project water shorted because of bad hydrology in a given year.

That is also the case for the oft-cited Dolores Water Conservancy District, which has junior water rights to the supply provided by McPhee Reservoir that is part of the Bureau of Reclamation’s Dolores Project. In contrast, the adjacent Montezuma Valley Irrigation Company has pre-Colorado River Compact water rights and its access to the same water source is relatively unlimited. The argument of the Upper Basin states about using less water in dry times applies in many local settings, especially in the local context of prior appropriation water rights. The argument is certainly logical.

But when one considers the regional scale of the entire Upper Basin, the argument is not supported by the data in the Bureau of Reclamation’s Consumptive Uses and Losses reports.

Our review of those data suggests that, on average, overall Upper Basin use is slightly greater in dry years, and less in wet years. While questions have long been raised about these data, they are the best that we have and, more importantly for this discussion, they are the data that the Upper Colorado River Commission has been using in support of its argument.

Here’s what the reports show for the 21^st century concerning total Upper Basin consumptive Uses less net evaporation from the CRSP Initial Units (Lake Powell, Flaming Gorge, and the Aspinall Unit):

• in the five driest years ( 2002, 2012, 2013, 2018, 2020), the average was 4.06 MAF/year.
• In the five wettest years (2005, 2008, 2011, 2017, 2019), the average was 4.01 MAF/year.
• in the middle 11 years (the remainder), the average was 3.81 MAF/year.

Upper Colorado River Basin agricultural water use in wetter and drier years. Graph by Jack Schmidt, Utah State University

Importantly, a scatter plot of Upper Basin agricultural water use since 1981 shows, in general, the opposite of what is being claimed. While agricultural use varies greatly from to year, in general, use has been greater in dry years and less in wet years.

In this plot, the estimated natural flow at Lees Ferry (a good representation of whether any individual year was wet or dry) is plotted against the summed agricultural use of water by all of the Upper Basin states.  This simple analysis provides results counter to the assertion of the Upper Colorado River Commission in the sense that agricultural use of water was greater in years of low natural flow at Lees Ferry and was less in years of high natural flow at Lees Ferry. Thus, this simple relationship indicates that agriculture uses less water in wet years and more water in dry years, which is exactly the opposite of the assertion by the Upper Basin community.

Upper Colorado River Basin water use over time. Graph by Jack Schmidt, Utah State University, based on USBR Consumptive Uses and Losses Reports

Another way of looking at this question is to consider the long term temporal trend. If the Upper Basin’s argument was correct, we would see a decline in agricultural water use in the 21^st century, because the river’s flow shrank during the aridification of the 21^st century. However, use has not decreased.

There are important nuances in the data. In the second year of some consecutive dry years like 2012-2013, the Upper Basin’s total consumptive use drops significantly, perhaps because local storage is depleted in the first year and doesn’t fully refill in the second year. This may be the situation in 2020-2021 as well.

Why do we view the argument as dangerous? Because Lower Basin interests can do the same math we have. They almost certainly already have. That leaves the Upper Basin with a fragile foundation for entering the negotiations over the compromises that are certain to be needed to modify the Colorado River’s allocation rules in the face of climate change.

Authors:

• John Fleck is Writer in Residence at the Utton Transboundary Resources Center, University of New Mexico School of Law
• Eric Kuhn is retired general manager of the Colorado River Water Conservation District based in Glenwood Springs, Colorado, and spent 37 years on the Engineering Committee of the Upper Colorado River Commission
• Jack Schmidt is Professor of Watershed Sciences and director of the Future of the Colorado River Project at Utah State University