A Story of Adaptation: Managing the Colorado River in an Uncertain Future

The Colorado River supplies water for 40 million people in the West. The basin stretches from Wyoming and Colorado all the way to the Gulf of California in Mexico, winding through several states that rely on its waters for irrigation, drinking, recreation, treatment and more.

Within that map lies a story — a story of changing landscapes as climate change and human consumption gnaw at the edges of the Colorado River Basin. The story of the Colorado is one of myriad questions for the future, and water researchers approach these arising issues from several angles in order to provide greater understanding to those charged with finding solutions.

The story begins with the agreements that govern water resource allocation in the basin — agreements that are expiring in 2026. With all eyes on new management options, Utah Water Research Laboratory faculty and students are addressing a variety of research needs.

Assessing Streamflow Data for an Uncertain Future

To find water management solutions for new Colorado River Basin agreements, decision makers run simulation models to evaluate alternative management options. They look at the impact of drought and declining runoff in the face of growth and environmental change, working to understand the availability and variability of future water resources in the basin. To run these models, they need streamflow data that reflects the uncertain future.

Working on a project funded by the U.S. Bureau of Reclamation, UWRL graduate student Homa Salehabadi developed a structured framework for assessing streamflow data to inform management options post-2026.

Planning and operation models require inputs of streamflow ensembles — sets of data over a period of time.

"Right now, there is no agreement on the best representation of future hydrologic conditions, and so there is no single best streamflow ensemble," Salehabadi said.

Ensembles based on historical data may not be sufficient for the future because climate is changing. Those based on climate change models give a wide variety of projections for the future, showing uncertainty in the models. Planners and decision makers have to face and accept this uncertainty. The storyline approach was developed to do just this.

“A storyline is a set of assumptions that describe plausible future conditions,” URWL Director David Tarboton said.

Under Tarboton’s guidance, Salehabadi developed storylines describing plausible future conditions in the Colorado River and sought out ensembles that matched the storylines.

“Storylines can be based on the past, climate model projections, a combination of these, or any other future conditions that the system may need to cope with,” Tarboton said.

Salehabadi assembled statistical metrics to evaluate available ensembles and quantify differences, searching for those matching storyline characteristics like persistent drought conditions.

She developed four storylines but couldn't find a matching ensemble for one. So she and Tarboton took a new approach, mixing historical information with paleo-reconstructed data and combining it with estimates for future streamflow decline to create a new ensemble representing a warming-driven declining streamflow future with increasing variability.

"We generated a new ensemble by considering future changes and non-stationarity along with the rich information from historical and paleo-reconstructed streamflow data," Salehabadi said.

Her work has been published in Water Resources Research and data is available on HydroShare. The Bureau of Reclamation is using her research as inputs in planning models and using her metrics to evaluate other data.

Salehabadi hopes her work can help decision makers find the best alternative management for the uncertain future.

"Hopefully, together we can find a way to sustainably manage and preserve this beautiful river," Salehabadi said.

Modeling Lake Mead Water Intake

Situated on the Colorado River just outside Las Vegas, Lake Mead is an important water resource for people in the valley. Intake structures beneath the lake take in water and pump it back up several hundred feet to be treated and distributed to residents.

But as Colorado River flow and subsequently Lake Mead water levels decline, that infrastructure has to be modified to function at lower levels.

UWRL professor Steve Barfuss is building physical scale models of one of the intakes and the low lake level pumping station, which is used when water levels are too low for the other two pumping stations.

Using 3D printed parts to increase detailed accuracy of the models, Barfuss examined flows at the current intake elevation and within the proposed range of lowered elevation, which means dropping the head of the intake where it sits at the bottom of the reservoir.

“The physical model allowed us to establish how low we could take the intake before we started sucking in gravel and rocks, and how low we could take the water level and not be dealing with vortices,” Barfuss said.

Like the drain of a bathtub, when the water level gets too close to the intake, it can create vortices, up to 6 feet in diameter, which start sucking air and debris into the system that then has to be dealt with.

Although a gentle vortex isn’t a problem for the system, it can still cause a disturbance on the surface of the water. The ideal for Barfuss and the managers at Lake Mead is to get the intake as low as possible to avoid these vortices on top without picking up sediment from the bottom.

When the lake level is low, the pump stations have to lift water much higher than they were designed for. A 9:1 scale model was used to observe how water levels are affecting the approach conditions to the pump, depending on how low the 32 pumps are extended.

Barfuss is ensuring the new extensions meet hydraulic standards, including potential for vortices, velocity profiles and fluctuations and flow circulation.

As climate change and human consumption continue to affect the Colorado River, its story will include adapting infrastructure to serve needs.

“As long as people live there and people need water, there will be these kinds of studies to evaluate how to get it from the river to the people,” Barfuss said.

Adapting to low flows and storage

The story of the Colorado is a story of less.

“We have to figure out how to live within our means,” said UWRL professor David Rosenberg, “while giving basin partners more flexibility and autonomy to manage their conflicting interests.”

Rosenberg’s team has three projects that seek to provide insights to turn win-lose tradeoffs on the Colorado into wins.

A first effort is adapting Lake Powell releases to low reservoir inflow and low storage. This may occur increasingly as the basin becomes more arid.

“Inflow becomes really, really important at low reservoir elevations because more of the water available for release comes from inflow rather than storage,” Rosenberg said.

He and his colleagues found that reducing releases to 95% of reservoir inflow can stabilize and recover storage. Tying releases to physical inflow also allows Reclamation to separate their interest to protect critical reservoir elevations from users interests to divide the flow above Lake Powell.

A second effort quantified tradeoffs at Glen Canyon Dam, where days of steady low releases allow aquatic invertebrates (bugs) to lay and hatch eggs but reduce hydropeaking value and lower funds to maintain infrastructure.

“We are suggesting that federal or state agencies such as Reclamation, National Park Service, or state fish and game agencies give ecosystem managers a budget to choose the number and timing of steady low releases and compensate hydropower producers for lost value,” Rosenberg said.

One potential experiment is to move days of steady low flows from summer to spring/summer months when hydropeaking value is lower and bug flows are not presently done. Managers can then monitor whether shifts increase algae production as the primary food for bugs, help small larvae in fall months, or support larger larvae right before they emerge in spring months.

In a third effort, Rosenberg and a colleague are looking at the strengths of the existing Lake Mead water conservation program and opportunities to improve.

“In my view, the Lake Mead water conservation program is the most successful and adaptive component of current Colorado River management,” Rosenberg said. “The program is also based on the assumption that annual Lake Mead inflow is 9 million acre-feet or larger.”

That assumption is challenged as the basin becomes more arid.

“Giving all users more flexibility and autonomy to manage their vulnerabilities to water shortages while stabilize and recover reservoir storage, that’s a win,” Rosenberg said.

They will soon test the approach using an immersive, online and collaborative model. Basin partners immerse in and personify water user roles. A model for Lake Mead divides reservoir inflow and subtracts evaporation. Partners then make choices to consume and conserve water in response to their available water, others’ choices, and the real-time discussion of choices.

“We are interested in why,” Rosenberg said. “Why do partners make decisions to manage their vulnerabilities and how do they adapt their strategies to changing available water?”

This immersive modeling follows a first use with 26 basin partners in summer and fall 2021 for a combined Lake Powell-Lake Mead system. That model also divided the inflow to Lake Powell. It also gave managers more flexibility to make pulse flows to the Colorado River delta. Tribal water users had more autonomy to use or lease their settled water rights. Basin managers also had more flexibility to release water from Lake Powell to advantage native fish of the Grand Canyon.

“Some of those ideas, they made it into proposals for new Colorado River operations post 2026 when current guidelines expire,” Rosenberg said.

Facing the Future

It takes a village — or in this case, a combination of universities, state and federal agencies, and water rights users — to find solutions for this precious resource. As reservoir storage and inflows continue to decline, that village looks to reliable research for insights into the current and possible future scenarios.

The story of the Colorado is a variable one, but it is not yet a tragedy. Research informing management decisions will help guide the future of the basin, and all those who rely on it.

More information can be found in the UWRL Annual Report