Brad Udall, a Senior Water and Climate Research Scientist at Colorado State University, spoke at a virtual meeting of the RNRF Washington Round Table on Public Policy on March 9, 2021. He discussed the imbalance between water supply and demand in the Colorado River basin, how climate change is exacerbating the issue, and the ongoing renegotiation of the river’s management guidelines.

Introduction and Background

The Colorado River basin extends into seven states (Wyoming, Colorado, Utah, Arizona, New Mexico, Nevada, and California) as well as Mexico, along with the land of 29 Native American tribes. The American portion of the basin represents 8% of the area of the lower 48 states. Altogether, about 40 million people, including the populations of all major cities in the Southwestern U.S., rely on the Colorado for some portion of their water supply. The river is used heavily for municipalities as well as agriculture, with about 4.5 million acres of irrigated land in the basin.

The water supply in the river is often measured by the water levels in its two major reservoirs, Lake Mead and Lake Powell. These are the two biggest reservoirs in the U.S. In order to maintain sustainable levels in these two reservoirs over a long time period, withdrawals from the river must equal the supply being provided by the river’s flow. This was the case in 2000, when the combined contents of the reservoirs were over 90% full. Since then, their water level has dwindled to less than 50% due to a “structural deficit” – demand for the river’s water consistently outpacing supply. This is due in large part to the fact that over the past 20 years, the basin has been experiencing its worst drought on record. The flow of the river has decreased from ~14.75 million acre-feet (maf) to ~12.4 maf. Even before the drought began, water demand was high in the basin; since about 1990, it has not reliably reached the ocean.

While the current situation in the watershed is usually described as a drought, a lack of precipitation is really only half the story. Regional temperature increases, exacerbated by climate change, have also had a significant impact on the reduction of water availability. Udall noted that evaporative losses will only become more severe as climate change worsens. The Southwest is already one of the quickest-warming areas of the country, a trend that is expected to continue. The risk of multidecadal droughts will also continue to drastically increase in coming decades. The 2000-2018 period was the second-driest 19-year period in the basin since 800 AD. While this is partially attributed to natural variation, researchers have said that 50% of the decrease in soil moisture can be attributed to anthropogenic climate change. Climate change has turned what would likely be a moderate drought into an extreme, historic drying event. Aridification and heating, along with reduction in precipitation, are causing drastically drying conditions in a river basin that tens of millions of people rely on for their water.

Historical Management of the River

In 1922, to fully allocate use of the river’s water, the basin states agreed to the Colorado River Compact. This agreement still serves as the basis for the Law of the River, which is the set of rules for the river’s allocation and management. In response to the “hot drought” happening since 2000, new modifications to the Law of the River have been necessary to prevent the reservoirs from becoming depleted. The first of these, called the Colorado River Interim Guidelines, went into effect in 2007. These guidelines set out a series of complicated rules for how Lakes Powell and Mead are operated, allowing different quantities of water to be released from them when they are at certain elevations. They constrain use of water when the reservoirs are low. One innovative structure used to accomplish this is “intentionally created surplus,” which allows parties in the lower basin to store their water in a sort of “bank account” in Lake Mead.

Around 2013, it was becoming clear that persistently dry and hot conditions were rendering the 2007 Interim Guidelines insufficient. A new agreement was necessary. As a result, two new “Drought Contingency Plans” (DCPs) for the Upper and Lower Basins were adopted in 2019. Early in 2021, for the first time, drought conditions in the river reached the point where the DCPs’ provisions were activated. Udall noted that these agreements made some progress toward making the river’s use more sustainable but were not a permanent solution.

Future Management of the River

Udall finished his presentation by discussing future prospects for sustainably managing the river in these drying conditions. In 2026, the 2007 Interim Guidelines and DCPs expire. The seven basin states, 29 tribes, Mexico, and the federal government have already begun the multi-year process of renegotiating a new set of guidelines which will be adopted in 2027. The following are some central considerations for a successful new agreement described by Udall.

The Upper Basin’s “Delivery” Obligation

Among the problems that stakeholders are aiming to resolve is the nature of the Upper Basin’s delivery obligations. There is a clause in the original Colorado River Compact that says that the Upper Basin shall not allow the flow of the river to decline below 75 maf every ten running years. However, it is not clear if this obligation is really a “delivery” obligation or if it is a “non-depletion” obligation. If it is a delivery obligation, that means that the entire reduction of flow coming from the Upper Basin due to climate change falls on the Upper Basin to solve. Clearly, this was not the intent of this clause in the original 1922 compact, and the Upper Basin states are making this argument.

Tribal Issues

Native American tribes are expected to have a much more significant role in the renegotiation of the Interim Guidelines than they have had in previous decision-making processes for management of the river. There are 29 tribes in the basin. Altogether, they have a right to control about 20% of the basin’s water. This right derives from a 1908 Supreme Court decision which issued the “Winters Doctrine.” This doctrine said that when the federal government creates a reservation of land for a tribe, implicit in that reservation is a water right.

However, tribal interests were still left out of the 1922 compact, and many of their rights remain unquantified. Even in the 21st century, the tribes in the basin were not invited to participate in the 2007 Interim Guidelines negotiations or the 2012 Basin Study. The 2019 DCPs were an important development in the inclusion of tribes in river management discussions after their needs and rights had been historically ignored. For the first time, these 29 distinct tribes were acting collectively and were included in the planning process. The DCPs were also the first time that a tribe agreed to accept a monetary payment in exchange for using less than their full water right. Inclusion of tribal interests in the renegotiation of the Interim Guidelines is expected, and will be essential to the new agreement’s success.

The Structural Deficit

Fundamental to the dilemma faced by basin stakeholders in this renegotiation process is the “structural deficit.” This is, quite simply, an imbalance between the supply of and demand for water in the basin. Since 2000, demand has outpaced supply. Demand reductions are challenging because once a water user has access to a supply of water, it is difficult to get them to relinquish it. The supply-side is more challenging to address. In the absence of cooler temperatures and more precipitation ­– conditions increasingly unlikely as climate changes — it is difficult to create more supply. It is easier to change consumption patterns than it is to change the hydrology of the river. Without demand reductions in the Upper and Lower Basins, there is a high probability that the amount of water in the reservoirs will continue to fall.

Udall referenced a recent study that found that the Upper Basin’s water demand is unsustainably high. Despite this finding, parts of the Upper Basin actually want to increase their demand, which in the face of declining flows is an issue that will need to be addressed in the negotiation process. Demand Management measures, by which water users can voluntarily accept money in exchange for reducing their water consumption, will likely be part of the solution in the Upper Basin but caps on demand may also be necessary to ensure that the delivery obligation is fulfilled.

In the Lower Basin, the Central Arizona Project diverts water from the Colorado River into Arizona, providing water for an area including the cities of Phoenix and Tucson. As a part of the original agreement that permitted this project, it was agreed that if there ever was a shortage of water in the basin, Arizona would bear the brunt of demand reductions. Demand reductions will likely be necessary in the Lower Basin but Udall noted that it would be difficult in practice to mandate that they all come from Arizona. Solving this dilemma will be a part of the new Interim Guidelines negotiations. One method that may be used is to begin charging evaporative losses to state water budgets in proportion to their use. Currently, evaporation is being charged to nobody, which is a part of the overuse problem.

Guidelines for Successful Renegotiation

Udall also identified other steps that can be taken by stakeholders to work toward a successful new set of interim guidelines. First, he emphasized the importance of good science. Realistic climate and hydrological modelling are necessary to inform the negotiations. Udall noted that many of the models being used by watershed states are overly optimistic with regard to future hydrology. Beginning the negotiations with inaccurate presumptions about the future of the watershed are setting the new agreement up for failure. While the renegotiation is a political process, it needs to be informed by most accurate scientific information possible.

Because the structural deficit is a basin-wide issue, Udall advocated for the use of a combined metric that adds the quantity of water in Lakes Mead and Powell. This would be a more accurate way to gauge water shortages because the water in the reservoirs individually is less important than the total quantity between them when informing the management of the entire river basin. He also said that using clear language in negotiations is critical. For instance, one should never inaccurately say that the Colorado River Compact itself is being renegotiated. It is only the Interim Guidelines that are being replaced; the Compact remains the foundation for the river’s allocation.

The renegotiation process is more than just a group of stakeholders sitting around a table, working out a plan for the river. It is a series of large and small meetings, some more formal than others. Since not everything is negotiated in official sessions, there is room for behind-the-scenes discussion while also maintaining transparency. During the round table’s Q&A session, Udall mentioned that river management issues under discussion will be reported by many talented journalists, who will bring transparency to the process for interested parties.

Ultimately, the process of renegotiating the Interim Guidelines requires a balancing of political, economic, environmental, and societal values. Climate change is the defining issue of our time, and it is at the center of these water issues in the American West. While one can easily become disillusioned by political processes, especially in the realm of climate and environmental issues, Udall ended on a note of optimism. While the solutions are not all clear, there are good relationships among stakeholders, which will form a solid foundation for successful negotiations.

– Stephen Yaeger, RNRF Program Manager

The PowerPoint Udall used during his presentation can be found here.

In his presentation, Udall referenced a series of studies about the climate and hydrological conditions of the Colorado River. They can be found at the following links:

Increasing influence of air temperature on upper Colorado River streamflow

The twenty‐first century Colorado River hot drought and implications for the future

On the Causes of Declining Colorado River Streamflows

Unprecedented 21st century drought risk in the American Southwest and Central Plains

Large contribution from anthropogenic warming to an emerging North American megadrought

Colorado River flow dwindles as warming-driven loss of reflective snow energizes evaporation

When is Drought not a Drought? Drought, Aridification, and the “New Normal”

Alternative Management Paradigms for the Future of the Colorado and Green Rivers

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