The West’s historic drought in 3 maps

By John Keefe and Rachel Ramirez, CNN

As the Pacific Northwest prepares for record-breaking heat, vast swaths of the West are experiencing a historic and unrelenting drought, the worst in the region in at least 20 years.

The most severe drought is centered in the Southwest in California, Nevada, Utah and Arizona. But areas of extreme and exceptional drought extend north as well into Oregon and Washington, where oppressive weekend heat will dry out the ground and vegetation even more.

Climate change is playing a key role in these compounding crises: Drought and extreme heat are fueling wildfires; reduced snowpack and the lack of substantial precipitation are exacerbating water demands for millions of people, as well as agriculture, ecosystems and deteriorating infrastructure.

In addition to mandatory water restrictions already in place, even stricter cuts are looming amid the drought in some states as water levels plummet along the Colorado River.

Current drought

More than 25 percent of the West is in an exceptional drought, which is the most severe category used by the US Drought Monitor.

The West has already experienced one significant heat wave this summer, with more expected in coming months. Scientists say drought and heat are part of a vicious climate-change feedback loop: hot weather leads to drought, drought leads to hot weather and so on.

“Climate change is loading the weather dice against us,” Katharine Hayhoe, a climate researcher and the chief scientist for the Nature Conservancy, told CNN. “We always have a chance of extreme heat, particularly in the summer: but as the world warms, we see that summer heatwaves are coming earlier, lasting longer, and are becoming hotter and more intense.”

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.

Rainfall outlook

The West experienced extremely low rain and snowfall over the past year, compounded by drastically high temperatures. Less rain and increasing heat waves have led directly to drought conditions and water shortages.

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.

As drought conditions have worsened in 2021, hundreds of stream and river locations are experiencing below-average flow. More than 50 percent of the western monitoring stations reported lighter-than-usual flows.

Changes in streamflow affect the water supply for our own municipal use, crop irrigation and power generation.