LOGAN — Scientists can now predict drought and overall water supply on the Colorado River years in advance, according to a new study published by researchers at Utah State University.
The team of scientists believe long-term “ocean memory,” in conjunction with atmospheric effects and the influence of land systems, correlates with cycles of drought in parts of the western U.S., which then leads to water shortages on the Colorado River.
Similar to how El Niño and La Niña are predictors of weather, shortages of water on the Colorado River are preceded by fluctuating temperatures in specific oceanic areas, including tropical Pacific cooling, north Pacific warming and southern tropical Atlantic warming.
“Two years before or three years before, oceans show some specific patterns,” said Yoshimitsu Chikamoto, an associate professor at USU and the study’s lead researcher. “It’s sort of a propagating prophecy.”
Unlike the atmosphere, which is highly variable, ocean temperatures are much more predictable. They fluctuate less frequently, which allows the scientists to forecast annual water supply on the Colorado River up to three years in advance.
Additionally, land systems, such as vegetation, soil, groundwater and perennial snowpack, help filter out the variable precipitation so that the scientists’ predictions are more accurate.
The predictions on water levels were based on a coupled climate model. Typical climate models are generally one of four different types: atmosphere, land, ocean or sea ice, said Chikamoto.
For its study, the research team merged all four climate models and were able to predict soil moisture. They took that idea and then forecast stream flow in the Colorado River.
If the scientists are able to accurately forecast water levels years in advance for such an influential river, it would give policymakers a powerful new decision-making tool.
The Colorado River, stretching 1,450 miles, is one of the longest and most important water bodies in the U.S.
In 2012, an estimated 40 million people relied on the Colorado River for drinking water, recreation and work.
According to a 2014 study done by researchers at Arizona State University, “in excess of 16 million jobs in the Basin Region rely on the availability of Colorado River water at current availability levels each year.”
As such, prolonged water shortages can have huge negative impacts on Western states, including in sectors of agriculture, forestry, energy, food security, drinking water and tourism, according to the study.
The researchers analyzed data from years where there were water shortages on the Colorado River and found that “severe shortages correspond with agricultural losses and high fire activity in the Colorado River basin.”
Larissa Yocom, an assistant professor at USU and co-author on the paper, helped collect applicable fire data for the study.
“The main result of Yoshi’s study is really about that Colorado River watershed and how much water is available,” she said. “But he did find this link with fire. That means that this long-term forecasting tool might have other applications, like forecasting fire seasons.”
As the study was released during a historically active wildfire season, this tool could be a major benefit in the near future.
“We don’t have a way to predict how big the fire season will be very long before the season,” Yocom said. “So basically this paper represents a first step in trying to develop a longer-term forecasting tool. I think that it would take a little bit more research to figure out if it is really useful on a yearly basis to predict what the fire season is going to look like. But if it could, it would just be another tool for managers to use as they’re thinking about the upcoming season.”
The agriculture industry, a main user of water resources, could also be a beneficiary of the research team’s work.
“Somewhere between 70 and 80% of the water that is diverted — is used in the state of Utah — goes to agriculture,” said Matt Yost, an assistant professor at USU and co-author of the paper. “Subsequently, agriculture is the most impacted by drought, in many cases. So for farmers, irrigators, people that are using the water to grow crops, if they know in advance that water supply may be less than optimal — if we’re headed into a drought — then there are some decisions they can make to prepare for that.”
For farmers, that could include changing irrigation systems, investing in new technology or planning their crop rotations to feature plants that need less water, he said.
On the irrigation side, rationing water could be a precautionary measure if people were forewarned about an oncoming season of drought.
Yost compared it to preparing for an economic recession.
“Everyone feels the impacts of drought, but it affects everyone in slightly different ways,” he said. “I think of it like you and I, if we knew that a recession was coming next year, what would you do? You’d probably start trying to get your finances in order, you would start cutting back on expenses, you would do things to prepare for hard times. And for the everyday person, that’s going to vary a ton, too.”
While the modeling process took a year to complete, with an additional year taken to analyze the data, Chikamoto said repeating the process every three years is possible, under certain conditions.
“Technically speaking, it is possible,” Chikamoto said. However, more resources would have to become available to make the project truly operational going forward.
He also said the methodology used in the study could potentially be extrapolated for other bodies of water, including the Great Salt Lake and the Columbia River.