Russ Cook and his family stands next to severely damage vehicles swept away during a flash flood Tuesday, September 15, 2015, in Hildale, Utah. AP Photo/Rick Bowmer

Tuesday’s deadly torrents are reminders that western states need new models for water storage.

Two flash floods that struck southern Utah Tuesday brought a greater loss of life than any weather event in the state’s history.

12 members of two related families were killed in Hildale, a small town near the Arizona border. They’d gone out in their van to watch creek water rise and got caught in what others described as a “wall of water.” At least six hikers trekking the narrow slot canyons of Zion National Park, about 20 miles north of Hildale, were also swept up in a separate torrent and died.

Flash floods aren’t uncommon in the Beehive State. But storms like Tuesday’s are indicative of more intense, less frequent downpours that Utah—and virtually all of the West—can continue to expect because of climate change. Though rainstorms in any form might seem like a good thing for arid states, severe flash floods are actually part and parcel with the drier future the West faces. Right now, most of Utah is suffering from moderate to severe drought.

”Hildale got 50 percent of their annual precipitation in just one four-hour period,” says Brian Mcinerney, a hydrologist with the National Weather Service who specialized in the Southwest. “That might seem like they did well with drought conditions. But in reality, they’re still going to have water shortages.”

Flash floods tend to tear through small geographic areas that often lack the capacity to store large quantities of rainwater. And the water moves too quickly and intensely to replenish groundwater basins. Utah, like California, has traditionally relied on mountain snowpack and gentle, frequent rainfall for much of the state’s water supply.

But with near-record-low snowfall, that model is going to have to change. Mcinerney says that the state needs options where water won’t evaporate quickly, such as optimized groundwater storage, “shade balls” on top of existing reservoirs, and possibly, more dams.

“We have an uncertain future in many respects,” he says. “We have less rainfall, more intense, localized storms, and a population increase in Utah where numbers are anticipated to double. Where are they going to get water from?”

It’s a hard question that faces all of the West.

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