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SALT LAKE CITY — It's already well established that the West is experiencing its worst drought in 1,200 years. That figure is based on overall soil moisture content during the past two decades, matched to tree ring evidence from about 800 A.D.
But what has that looked like in terms of weekly drought conditions?
The National Centers for Environmental Information published a new interactive map Wednesday showcasing dry conditions across the U.S. over the past 20 years, based on a study published last month in the International Journal of Climatology. The study analyzed historic data collected by the U.S. Drought Monitor, which was only created in 1999.
"Using the (drought monitor) to characterize past drought ... paints a more complete picture of its nature and impacts," National Centers for Environmental Information officials wrote Wednesday.
Utah's fewer but longer droughts
The data presented on the map is from 2000 to 2019, so that means the current drought Utah is facing, which began about this time two years ago, isn't represented in the data. That said, the information shows what one may suspect just from experience within the ongoing megadrought.
Utah hasn't had as many drought events as states in the Southwest or even parts of the East; however, the average length of a drought event is significantly longer in the Beehive State and across the West.
Take the Salt Lake City area, for example. It has had 10 drought events over the past 20 years, which is 16 fewer drought events than the San Antonio area in Texas. However, the average length of Salt Lake City's droughts is 53.6 weeks, or a little more than a year, while the San Antonio droughts average 19.35 weeks, which is less than a half-year in length, on average.
Salt Lake City isn't even the worst spot for droughts in Utah. The average lengths of droughts increase elsewhere in the state, exceeding 80 weeks in parts of north-central Utah. That's an average of over a year and a half. In fact, all of Utah's grids on the map had fewer than a dozen drought events in the past 20 years, but each one averages between 40 and 85 weeks in duration.
That puts the current drought above average, even megadrought, terms. The ongoing drought event began after an abysmal spring, precipitation-wise, in 2020. That weather pattern carried into summer and fall, resulting in Utah's driest year on record. Even though it became less severe at times in the fall and winter last year, the drought is now picking back up in intensity and is severe enough that Gov. Spencer Cox last month ordered an emergency drought declaration for the second-straight year.
Western Nevada, however, takes the cake in the drought length category. The western portion of the Great Basin east of the Sierra Nevada range has the longest droughts in the nation. For example, the Fallon, Nevada, area has had only four drought events, but those average 184.5 weeks in length, which breaks down to about 3.5 years per event.
What about drought severity?
Given the West's 20-year plight and the length of every drought event, it may also not surprise anyone that the West dubiously leads the nation in weeks spent in extreme drought, or worse, status. Every drought the region faces typically ends up in extreme or exceptional status, which is why most of Utah — and the West — has spent at least a year's time in the worst drought categories over the past 20 years.
There are chunks of Utah that have spent over 96 weeks in a drought, as well.
"Portions of the U.S. that have spent up to two years in (extreme) or greater drought extend from parts of California over the Rockies and into New Mexico, Texas, and the Oklahoma panhandle," the authors of the International Journal of Climatology study wrote. "This diminishes to less than a year for most of the eastern U.S., with an exception of Georgia and portions of Alabama and the Carolinas."
Again, this is before the current drought. The U.S. Drought Monitor lists over half of the state in extreme drought status, after nearly 60% of the state reached exceptional drought status by mid-May last year — showing that the current drought is above-average, even in the age of the megadrought.
When droughts start and end
What complicates Utah's droughts is they aren't as easy to predict as in other parts of the nation.
While most U.S. droughts start in the summer, Utah's droughts tend to start in the winter, spring and summer, depending on where you're at in the state. Northern Utah is a mix of spring and summer, while droughts in southern and eastern Utah mostly begin in the winter and spring.
They tend to end either in the winter or spring instead of the fall, as is in the case for areas east of the Rockies. It means the current drought in Utah could end at any season but it'll most likely linger into at least this winter.
However, that remains to be seen. Of course, it wouldn't be the end of the megadrought, either.
That's really the case for every part of the country, though, as what's known about droughts is changing as a result of climate change, National Centers for Environmental Information officials add. Some areas are receiving "more severe, frequent or widespread, or a combination of these (droughts)," such as the West during the 20-year megadrought.
Federal climate experts contend the historic information of the past two decades is still valuable in showing what to expect as this happens.
"Though drought is not preventable, characterizing and understanding past drought allows federal, state and local entities to better prepare, respond and minimize drought impacts when it does develop. Sustainable water management planning is an example," they wrote. "This study also provides a basis and framework for continued study of drought in the 50 states and Puerto Rico, its evolution and strategies for resilience."
