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Want to test a theory on how to fix the Colorado River’s drought issues? There’s a model for that

A team of California researchers have developed a new way of estimating the economic impacts of water-saving efforts in the enormous basin. They’re turning it into an online site that everyone can use
Kayakers approach Two Rivers Park, where the Roaring Fork River meets the Colorado River, in Glenwood Springs, Colorado, on Aug. 20, 2023. (Shannon Mullane, The Colorado Sun)

Everyone from policymakers to armchair warriors has a theory on the best way to solve the Colorado River crisis. Soon they’ll have a chance to test out their ideas.

The Colorado River’s flow is dropping – it’s about 18% lower in the 21st century than it was in the 20th century – and that’s a big deal to the 40 million people who depend on it for water across the West. But solving the crisis gets complicated, quickly. That’s where a team of researchers at the University of California, Riverside, think they can help. They’ve developed a new way of looking at water-saving efforts across the enormous basin, and they’re turning it into an interactive map and dashboard that everyone can use.

“It doesn’t solve the conflicts, but it helps provide options,” said Mehdi Nemati, assistant professor of environmental economics and policy at UC Riverside. “And as we know, there’s going to be conflicts coming up.”

The team developed a mathematical model, called a hydro-economic model, to estimate the economic impacts of different policy decisions depending on climate scenarios. It’s brainy, to be sure: The researchers needed 339 pages of text, tables and graphs to explain the model.

Modeling is incredibly important for the Colorado River Basin. The people who decide how to store, release and distribute the river’s water have to have some way to plan days, months, years and decades ahead, said John Berggren, health rivers regional policy manager for Western Resource Advocates.

“You have to have some sort of way to analyze how your policies perform under a different suite of hydrologies, climate scenarios, demands and everything else that goes into a river system,” he said.

UC Riverside researchers are planning to release a user-friendly tool in early 2024 that allows people to play with climate change predictions, tweak how much water goes where, and focus on specific areas. The idea is that everyone, from farmers to gardeners, water managers, mayors and policymakers, can all hop online and test their Colorado River solutions.

That means people could look at estimated impacts of the recent proposal to cut water use by 3 million acre-feet in the Lower Basin, including Arizona, California, Nevada and tribal nations.

Or policymakers could look at the System Conservation Pilot Program in Colorado, which in 2023 only saved 2,700 acre-feet of water across 22 farms and ranches in Colorado and 37,810 acre-feet total in Colorado, New Mexico, Utah and Wyoming. That program is continuing, and with the model, people could decipher which geographic areas and crop types might save the most water.

It could also help basin negotiators who are tasked with setting up the governing rules for the basin’s biggest reservoirs, Lake Mead and Lake Powell, for years to come, Nemati said.

“All of these policies are being proposed – all these cuts are being proposed – what are some of the trade-offs between these different sectors as we move forward, especially with the negotiations coming up?” he said.

The first model to include economic impacts

The UC Riverside model is the first of its kind in the basin – at least as far as the researchers know – but similar models have been used in river basins in South Africa, Spain and around the world.

There are other models used in the Colorado River Basin, but they don’t combine information about the water system with economic impacts.

The Bureau of Reclamation is creating its own user-friendly web tool, which will allow users to analyze how their policy ideas perform under different climate scenarios in the short and long term. It’s meant to help people engage in the federal process to plan for the river’s future after 2026, when the current operating guidelines expire for lakes Mead and Powell.

The Colorado Basin River Forecasting Center, based in Salt Lake City, is charged with providing forecasts for the basin that help users, like the Bureau of Reclamation, make water management decisions.

The center focuses on streamflow under various conditions and time frames, but it doesn’t account for economic costs. Those are very difficult to quantify, said Paul Miller, service coordination hydrologist at the center.

“Sometimes it’s really hard to put a value on things. For instance, how much is an endangered fish ‘worth’?” he wrote in an email. “Or how ‘valuable’ is restored habitat for threatened species? Most people would agree that there is value to this, but putting an economic cost on it is difficult.”

The UC Riverside model mainly includes economic data for agricultural, urban water use and hydropower production. For example, the model uses data from 2.6 million acres of irrigated land, out of the 5.5 million acres in the basin, to make projections. The sampled areas span seven states, divert 8.9 million acre-feet of water and account for almost $1.8 billion in net income. One acre-foot supplies enough water for two to three households for one year.

The model uses economic data to help people estimate future trade-offs. Casual observers might simply say, just tell farmers to grow less water-soaked alfalfa or to use less water.

But there are ripple effects: When a farmer changes crops, it can require expensive new equipment, more debt and time investments to prepare cropland. If a farmer stops growing crops on acres of land to cut their water use, it affects their bottom line and it can mean layoffs for workers or fewer local jobs.

The UC Riverside model also accounts for environmental water use, and the Colorado River water used by 30 Native American tribes in the basin and two states in northwestern Mexico. It incorporates estimates for how populations will grow and what crops are being used on farms.

Predicting the river’s future is enormously complex, and there are so many variables that there is always uncertainty. That’s why water engineers have a saying: All models are wrong; some are useful, Berggren said.

Models can, however, give a range of possibilities that can help water managers plan into the future – with more certainty in the next six months than the next 10 years. When any model looks at Western water, the big factor is how it accounts for climate change, he said.

“A robust model needs to be able to look at a range of climate scenarios from slightly bad to really, really, really bad,” Berggren said. “If a model can’t incorporate that range of climate scenarios, then it’s kind of useless. If it uses the same climate assumptions of the past couple decades, then that doesn’t account for the changes we’re going to see in the future.”

Climate change is a key part of the UC Riverside model, which looks at temperature, precipitation, evaporation and other environmental factors to estimate possible reductions in the river’s flow.

Temperatures in the basin are expected to increase by 1.8 degrees to 7.2 degrees Fahrenheit over the next 50 to 100 years depending on the projection. That increase would cause the river’s flow to shrink by 6% to 31%, according to UC Riverside’s research paper.

“Because there’s so many factors and so many elements to this, the goal is to show the policymakers, what are some of the options? And what are the trade-offs?” Nemati said. “Also managers in different cities, farmers, anyone – they can define their own sets of policies, and we can test that. That’s the hope.”

The Colorado Sun is a reader-supported, nonpartisan news organization dedicated to covering Colorado issues. To learn more, go to coloradosun.com.

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