The Western US experienced extreme drought this year that severely strained water resources and primed the landscape for perilous wildfires.
In California, this summer’s drought was the most extreme in the state’s entire 126-year record, with July 2021 as the driest month ever since data gathering began in 1895. Across the region, the magnitude of the drought hovered at or above 90% since June, with several states entirely in drought.
On the Colorado River, Lake Mead and Lake Powell — two of the country’s largest reservoirs — have been draining at alarming rates, threatening the West’s water supply and hydropower generation in coming years.
In California, a hydroelectric power plant at Lake Oroville was forced to shut down due to low water levels for the first time since it opened in 1967. In other parts of the state, thieves broke into secure water stations, tapped into fire hydrants and threatened farmers to steal water. And in Oregon, a reservoir shutdown pitted communities against one another, with a rural farming group threatening to take water back by force.
Scientists say the West’s historic, multi-year drought is a clear sign of how the climate crisis is affecting not only the weather, but also communities’ water supply, food production, electricity generation and livelihoods.
T.J. Atkin’s family has been in the cattle ranching business for nearly a century. He carried on the legacy as a rancher and now operates two properties in Utah and northwest Arizona, both of which experienced severe drought this summer.
Since the family business started, he said, a drought has never hit their operations as hard as it did this year.
“Everyone else I’ve talked to says in 85 years, it has not been this bad,” Atkin told CNN in June. “We have 85 years’ worth of our own drought data that says we’ve never done this … not to this extent.”
Climate researchers say two major factors contributed to this summer’s severe drought in the West: the lack of precipitation and an increase in evaporative demand, also known as the “thirst of the atmosphere.” Warmer temperatures increase the amount of water the atmosphere can absorb, which then dries out the landscape.
This summer may just be a preview of what’s to come: Global scientists reported in August that because of the climate crisis, droughts that may have occurred only once every decade or so now happen 70% more frequently.
The findings reflect recent data from the National Oceanic and Atmospheric Administration, which found that drought months in the West are becoming the new normal, with rainy months coming fewer and farther between.
In August, the US Bureau of Reclamation declared a water shortage on the Colorado River for the first time, triggering mandatory water consumption cuts for states in the Southwest beginning in 2022. The following month, it announced there’s a 3% chance Lake Powell could drop below the minimum level needed to allow the lake’s Glen Canyon Dam to generate hydroelectricity next year. In 2023, the chance of a shutdown grows to 34%, according to the bureau’s projection.
There is also a 66% chance that Lake Mead could drop below the critical threshold of 1,025 feet above sea level in 2025, the bureau said. If water levels stay below that critical threshold, it would trigger deep water cuts, potentially affecting millions of people in California, Arizona, Nevada and Mexico.
As the planet warms, drought and extreme heat will also fuel deadly wildfires. Multiple studies have linked rising carbon dioxide emissions and high temperatures to increased acreage of burning across the West, particularly in California.
Scientists say heat and drought are inextricably linked in a vicious feedback loop that climate change makes even harder to break: heat exacerbates the drought, which in turn amps up the heat. As temperatures surged to the triple digits this summer, the sun baked out what little moisture there was left in the ground.
The need for precipitation was dire this year. Years of low rainfall and more intense heat waves have fed directly to this summer’s drought conditions and water shortages.
What the West Coast needed were the strong storms that draw moisture from the Pacific Ocean, often referred to as atmospheric rivers. These storms are crucial in determining whether California is going to end up in drought. And in the last two years before this summer, only one such storm brought precipitation to California last winter.
Then in October, California and parts of the Pacific Northwest got a taste of the rain it was looking for. Because of the recent rain, the Drought Monitor noted that much of the West is now experiencing long-term drought conditions, rather than both short- and long-term drought.
In the Southwest, were the summer rain brought some relief, researchers at NOAA say that the drought there will get worse with La Niña — a natural phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator, which causes shifts in weather across the globe.
La Niña typically causes the jet stream — upper-level winds that carry storms around the globe — to shift north away from the Southwest. That means less rainfall for a region that desperately needs it.
As climate change accelerates and winter temperatures increase, snowfall will decrease. High-elevation snowpack serves as a natural reservoir that eases drought, storing water through the winter months and slowly releasing it through the spring melting season.
Stream and river flow
Streamflow, a measure of how much water is carried by rivers and streams, is another significant indicator of drought and its impact. Changes in streamflow affect the water supply for municipal use such as drinking and bathing, crop irrigation and power generation.
As drought conditions have worsened in 2021, hundreds of stream and river locations experienced below-average flow. Fishing restrictions have also been put in place on many rivers in Montana due to low flows and warm waters.
In Oregon and California, long-term drought conditions have adversely affected salmon populations and migratory birds, according to the Drought Monitor.
But now that the rainy season has begun, soil moisture and streamflows in the West are improving, particularly in the central and northern Great Basin, including in parts of Idaho, Nevada, and Utah, which have been entirely in drought throughout the summer.
Meanwhile, snowpack has also started to form across the northern Rockies as well as the Cascades, and even into parts of the Sierra Nevada, “but it is still early in the season to reap the benefits,” the Drought Monitor previously noted.
Still, according to a NOAA report published in October on the Southwest’s historic drought, the current drought could last into 2022 — or potentially longer.
“More widely, my guess is that for much of the West, the current extent and magnitude of this drought is locked in until at least mid-2022,” Justin Mankin, assistant professor of geography at Dartmouth College and co-lead of NOAA’s Drought Task Force, previously told CNN.
“Global warming is making the atmosphere over the West warmer and thirstier, such that even the rain and snow that was once normal may be too little to quench it,” Mankin said.
CNN’s Brandon Miller, Aya Elamroussi, and Stephanie Elam contributed to this report.