June 13, 2021 11:28:37 am
An intense drought is gripping the American West. Extreme conditions are more widespread than at any point in at least 20 years, according to the U.S. Drought Monitor, the government’s official drought-tracking service. And the hottest months of summer are still to come.
“It’s an alarming picture,” said Daniel Swain, a climate scientist at UCLA, who studies how global warming affects extreme weather events.
Across the region, reservoir levels are near record lows and mountain snowpack, which slowly releases water in the spring and summer, is largely depleted. In California, water restrictions are already in effect, with more widespread cuts expected. Dry soil conditions are already increasing fire risk.
The West is no stranger to drought, but climate change is making it worse. Severe dryness covered California and Nevada just five years ago, from 2012 to 2016, and the Southwest has been in drought for much of the past two decades, punctuated by rare wet years. Experts say this year is unusual because severe drought conditions are so widespread and have intensified quickly. They are likely to grow even worse.
The situation is especially dire in California and the Southwest.
Winter rain and snowfall usually bring most of California’s moisture for the year, but this winter was drier than usual, with warm temperatures arriving early this spring. The state is now in its dry season and is unlikely to see significant rainfall again until October.
“There’s a 100% chance that it gets worse before it gets better,” Swain said. “We have the whole long, dry summer to get through.”
In the Southwest, a late summer monsoon that usually provides about half of the region’s annual rainfall could bring some respite — if it materializes. Last year, the monsoon was more of a “nonsoon,” bringing only traces of rain.
High temperatures and not much rain
Large swaths of the West saw record-low precipitation over the past year, matched by significantly higher-than-usual temperatures.
David Simeral, a climate scientist at the Desert Research Institute and an author for the U.S. Drought Monitor, said conditions over the past 12 months had contributed to the rapid intensification of the current drought. Brutal heat lashed much of the region last summer, the Southwest monsoon failed to deliver substantial rainfall that year, and many western states got less precipitation than usual this winter, too.
While the West has long experienced boom and bust years for precipitation, climate change, caused by the burning of fossil fuels, is increasing volatility: It makes dry years drier and wet years wetter.
Higher temperatures have also directly contributed to the drought conditions and water shortages in recent decades. Warmer winters bring more precipitation in the form of rain rather than snow, decreasing snowpack, and more intense spring heat has caused the snow to melt earlier. Higher-than-usual temperatures also dry out vegetation and soil and can increase evaporation from reservoirs, putting added strain on the crucial Western water supplies.
Depleted snowpack and low reservoirs
Reservoir levels across the region are exceptionally low this year. So is mountain snowpack.
Lake Mead, the largest human-made reservoir in the United States, recently hit its lowest level since 1937, following years of decline. The lake, which sits on the border between Nevada and Arizona, is under growing pressure from the prolonged drought, climate change and growing population in the Southwest.
Across the region, reservoirs are struggling this year, especially in California.
Usually, melting mountain snowpack helps to replenish reservoirs, rivers and soils throughout the spring and summer. (You can think of snowpack as a sort of natural reservoir system that releases water over time.)
But in the Sierra Nevada of California and other parts of the lower West, snowpack melted early this year because of higher spring temperatures and other unfavorable conditions. Much of the runoff didn’t make it to reservoirs and streams at all because already-parched soils sucked up the water.
The agricultural sector in California has been particularly affected by water shortages, with federal and state allotments drastically cut. Farmers have had to destroy some water-intensive crops in hopes of saving others. At the California-Oregon border, the drought has pitted farmers against fish once more.
In some parts of the state, local officials have asked people to start conserving water. Big cities aren’t likely to see major water shortages this summer, but running out of water is a real possibility for some rural areas, especially those that depend on wells.
Jeanine Jones, the interstate resources manager for the California Department of Water Resources, said the current crisis exposes the need for drought forecasting and planning to consider the effects of climate change.
“We’ve now had two dry years,” she said, but “this is all occurring in the context of a longer period, a couple of decades, of generally dry and much warmer conditions.”
An outlook for fire ‘as bad as it can be’
Last year, the West Coast saw its worst fire season on record, with megafires burning in Washington, Oregon and California. Dry conditions have set the stage for another bad fire year in 2021.
High temperatures and low precipitation have dried out grasses, shrubs and other greenery, and soils are extremely dry.
Already, twice as many acres have burned in California as during the same period last year. The state’s fire season has expanded in recent decades, starting earlier and ending later than it used to.
“Not everything is predictable,” said Swain of UCLA, referring to events like the dry lightning strikes that ignited many major fires in 2020. “But of the predictable elements — how dry is the soil? And will it get better in the next months? — those are as bad as it can be.”
“Most of the west is at increased risk of large severe fires this year,” he said. “That may sound like a broken record, but maybe that’s the point.”
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