The U.S. Drought Monitor uses precipitation levels, soil conditions, reservoir volumes, and temperature to determine drought conditions at national, state, and regional levels.
Each week, the monitor releases a color-coded map – the darker the red, the worse the drought. The system is meant to guide emergency federal aid to affected farmers, ranchers, and communities, said Justin Mankin, an associate professor for geography at Dartmouth College.
“But,” he continued, “it's awfully hard to think about where you should put your resources to greatest effect if the map is just red everywhere, week on week. We should understand how the severity of drought is changing, owing to climate change.”
Mankin led a team of researchers at Dartmouth College that found parts of the American West have been in a category of drought, ranging from moderate to exceptional, much longer than U.S. Drought Monitor guidelines suggest they should. No area should have spent more than 20% of the last two decades in any category of drought, according to the federal government.
However, parts of Nevada, New Mexico, Arizona, and California have been in drought more than 70% of that time, according to the Dartmouth-led study published in the journal AGU Advances.
What’s more, Mankin and his team found extreme droughts today are much more harmful to water resources and crops than the droughts considered “extreme” 20 years ago.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
