Mar 24, 2021 - Energy & Environment

A very, very, very dry future for the U.S. West

Photo of Lake Mead

Photo: Justin Sullivan/Getty Images

The American West is in the midst of a punishing drought, and long-term conditions are only expected to get worse.

Why it matters: Much of the West has a deep history of decades-long "megadroughts" — and that was before the added drying effects of climate change. But with population in the region projected to continue growing, both water demand and carbon emissions risk an arid future for the West.

By the numbers: According to the U.S. Drought Monitor, nearly 40% of the West is currently in a state of extreme or exceptional drought, the two most severe categories, and barely 10% of the region is altogether drought-free.

  • The current drought began last year, which was the driest on record for Utah and Nevada, and among the driest for states like Colorado.
  • "By intensity, it would be about as bad as the U.S. Drought Monitor has shown in the last 20 years," climatologist Brian Fuchs of the National Drought Mitigation Center told USA Today recently.
  • And conditions aren't likely to improve in the near future given the ongoing contributions of climate change. NOAA's most recent Seasonal Drought Outlook predicts persistent dryness west of the Rockies, save for the Pacific Northwest, with drought affecting 74 million Americans.

Where it stands: The driest parts of the American West are already in the grips of a "megadrought," defined as a prolonged drought lasting two or more decades.

  • The ongoing drought is the result both of reduced precipitation, including less of the winter snowfall that replenishes water reserves, and punishingly high temperatures, which strips the soil of moisture.

The big picture: The American West has a long history of recurring megadroughts that dates back to well before humans started putting carbon into the atmosphere.

  • A study published last year used moisture-sensitive tree-ring chronologies to find evidence — backed by historical documents of the era — of a multidecadal megadrought in the U.S. Southwest during the 16th century.
  • That megadrought was the worst in the region for at least 1,200 years — with the second-worst occurring over the past 20 years.
  • And these events aren't necessarily rare — other research has shown evidence of five other megadroughts in the region between 800 and 1300.

Context: Drought — which T.S. Eliot aptly called "the death of the earth" — is different from other natural disasters in that it is slow to begin and slow to end, exacting its toll day by dry day rather than in the brief but concentrated form of a hurricane or an earthquake.

  • That toll adds up — between 1980 and 2020, drought cost nearly $250 billion in damages and killed nearly 3,000 people, making it the most expensive and second-most deadly natural disaster in the U.S.

What to watch: Drought is a product of how little rain might fall and how hot temperatures become, but also of how much water humans are taking from the environment.

This means that we're adding more and more people to the very region in the U.S. that has both a history of extreme, multidecadal drought and is set to get drier in the years to come thanks to climate change.

Yes, but: Total water withdrawals in the U.S. actually declined 25% between the peak in 1980 and 2015 — one sign of our ability to decouple growth from water use.

The bottom line: Multiple past civilizations have met their demise in part due to megadroughts, but with smarter water management and climate action, that doesn't have to be our fate.

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