Known for its glowing swaths of yellow, orange and red, the U.S. Drought Monitor has warned farmers, residents and officials across the country every week since 1999 of impending water shortages.
Backed by data on soil moisture, temperature, snow cover, meltwater runoff, reservoir levels and more, the map has become an essential tool for determining water supply prospects, declaring drought emergencies and deciding where and when to distribute government aid . other things.
But this crucial diagnostic tool is also struggling to keep pace with climate change, as longer and persistent dry spells ravage the American West and take an increasing toll on groundwater reserves and the Colorado River, according to a recent study published in the journal AGU Advances.
One problem, researchers say, is that the monitor was launched just as one of the driest periods in the Southwest’s history began, and was never adapted to the region’s growing drought.
“The product is essential, but in my view it is also undoubtedly affected by climate change,” said Justin Mankin, one of the study’s authors and an associate professor of geography at Dartmouth. “And we in the drought community need to have a conversation about what it looks like to think about drought monitoring in the context of an arid climate.”
The monitor provides an accurate and reliable snapshot of what is happening in the climate system at any given time, including a combination of global warming and La Niña conditions that are contributing to the drought in the southwestern United States, the study found. the study.
But its introduction happened to coincide with the start of a decades-long period of drought in the West, including the region’s driest 22 years in at least the past 1,200 years, known as a megadrought.
During that period, some parts of California experienced exceptional drought — the worst of the five possible categories — nine times more often than they should, according to the drought monitor’s probability. The areas were in that category 18% of the time – or over a period of almost four years – compared to the normal benchmark of 2%, the study found.
The findings raise questions about how the known rating can best address long-term trends, and whether a product designed for periodic anomalies can accurately capture a much larger, slower-moving crisis.
“These trends emphasize the theoretical guidelines of the product itself, and I would argue that it undermines its usefulness as a decision maker,” said Mankin, who was also a former co-leader of the National Oceanic and Atmospheric Administration’s Drought Task Force. .
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The monitor is indeed more than just a measure of drought. It is used to inform social and economic policy, including decisions regarding state and local drought declarations, federal funds for farmers and agricultural businesses, and other disaster-related assistance.
For example, the Farm Services Agency uses the Drought Monitor’s weekly updates to distribute certain relief programs, such as emergency haying and the Livestock Forage Disaster Program. The Internal Revenue Service uses it for some tax deferrals related to livestock farming, while the U.S. Department of Agriculture uses it to determine eligibility for low-interest loans.
But resources activated by exceptional conditions can quickly dry up if those conditions persist for months or even years, says Jason Smerdon, another author of the study and a climate scientist at Columbia Climate School.
“It’s an emergency, but a different kind of emergency,” Smerdon said. “If it stays dark red all the time, then short-term emergency response to address the challenge isn’t really the way to think about it. It is an emergency of a much longer, ongoing nature, which I think requires different planning and different planning. relief.”
Experts working on the Drought Monitor say they are open to the feedback and also acknowledge that the tool has its limitations.
“The Drought Monitor was never intended to be an indicator of climate change – it was intended to be a real-time assessment of drought conditions,” said Mark Svoboda, director of the National Drought Mitigation Center at the University of Nebraska-Lincoln, which produces the monitor in collaboration with NOAA and the USDA.
The monitor uses a “convergence of evidence” approach that pulls data from dozens of indicators every week, including measurements of precipitation, soil moisture, snow cover, snow water equivalents, stream flows, evaporation and groundwater and reservoir levels, he said. That means they are also somewhat bound by the limitations of those tools.
Every Thursday, more than 400 experts from across the country will review a draft of the update before publication and give their opinions on its findings. It is rare that such a product has so much input and also adds a bit of art to science, says Svoboda, who co-founded the Drought Monitor in 1999 and was its author for 17 years.
But the problem today is that it is not yet known whether the megadrought in the West represents a permanent climactic shift that could warrant a recalibration of the instruments, or whether even wetter days may lie ahead, he said. In regions that are already dry, who decides when small moisture shifts will reach a tipping point in a new era?
“We’ve seen multi-decade droughts, then we’ve seen a switch to a wetter regime,” Svoboda said. “So the real challenge right now, 20 years from now, because of climate change, is: will we never see the reversal? Should we therefore classify in a certain region and switch to a drier climate? That’s the real challenge.” The $100 billion question, and our indicators right now, are not going to answer that because we are not a forecasting tool.”
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The good news is that the monitor is generally adept at standardizing its classifications for regional variations, such as how an “exceptional” drought can have vastly different impacts in California than in a place like Vermont, Smerdon said.
But the weekly snapshot is also “not enough to think about where we are going and what we are doing in light of the increasing water pressure we are going to experience in the West,” he said.
For example, Southern California was never classified as in exceptional drought during the 23-year study period, the researchers found — despite the fact that millions of people in and around Los Angeles were placed under the strictest water restrictions ever amid the state’s three driest areas. years on record.
Additionally, the Drought Monitor currently shows that most of California and the Southwest are behind the worst stages of drought after two recent wet winters. But groundwater supplies are still depleted and the Colorado River has not yet fully recovered from more than two decades of drought, with Lake Mead still measuring only about 35% of capacity.
“Those are the central banks for the water economy of the West, but if you look at the map you won’t see that in any substantive way,” Mankin said.
Svoboda said current readings in the Colorado River region represent a “double-edged sword.” It’s unlikely that Lake Mead will ever reach full capacity again, but if you were to continue showing that on the Drought Monitor, the map there would remain red indefinitely.
“The challenge is always: You don’t want to cry wolf too quickly, but you certainly don’t want to wait for the wolf to eat you,” he said of declaring a drought. “And if you’re coming out of a drought, the same applies. The effects of drought can linger.”
Other tools, such as reservoir monitors from the U.S. Bureau of Reclamation and the California Department of Water Resources, are better equipped to measure water scarcity and supplies in the region than the Drought Monitor, he added.
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But there are potential ways to help the instrument evolve with the changing climate, including expanding the baseline to include wetter periods before the onset of the current megadrought, which would help smooth the bell curve and reduce the frequency of extremes, the study said. researchers.
Addressing a new ‘super-exceptional’ category could also help with its calibration. It’s a step that has already been proposed for other worsening climate events, such as a new ‘Category 6’ for hurricanes.
However, there are limits to that solution when it comes to droughts, which are difficult to tie to finite amounts of water, unlike hurricanes, which have no upper limit in effect, the researchers said.
Svoboda similarly said the Drought Monitor is limited by limited data on many of the products it relies on. Furthermore, changing the ‘normal’ would also mean that all surrounding policies – such as the Farm Services Agency’s assistance – would also have to change.
Such problems do not necessarily indicate shortcomings of the monitor, but rather underscore the need for a variety of tools, both he and the researchers said. The US Drought Monitor should not be the all-encompassing decision-making tool, and should continue to be combined with reservoir observations, snow surveys and other measurements to form a complete picture.
Mankin said he hopes the study can shed light on the need for long-term adaptation — and the increased possibility that California and other states will be in drought conditions far more often than ever before.
However, he and Smerdon stressed that the research should not undermine the value of the Drought Monitor – or the work of those who keep it updated week after week.
“Monitoring drought and keeping a sense of how the hydroclimate fluctuates in the United States is very important, and it has really been a game-changer to have it as a resource and for planning,” Smerdon said. “I just think it needs to evolve. We need to think about what an instrument like the Drought Monitor means in a changing climate.”
This story originally appeared in the Los Angeles Times.