One strong rainstorm may cause flash floods and backed-up storm drains, but it doesn’t end the drought that has plagued Utah this summer, according to a weather expert.
“This certainly helps, getting some rain,” said Jim Steenburgh, professor of atmospheric sciences at the University of Utah and an expert on mountain climate. “But we’re still way in the hole.”
Utah’s main water source is the mountain snowpack, Steenburgh said. “That’s our primary reservoir for water, so to speak,” he said. “There’s a lot more water in a wintertime snowpack in the spring than is produced by one of these thunderstorms.”
A big storm like Sunday’s, Steenburgh said, might produce a couple of inches of rain in a small area. On the other hand, “in the spring, you have a snowpack that might have 20 or 30 or 40 or even 50 inches of water stored in it. So there’s just no comparison between the amount of water available in the spring in the wintertime snowpack and what’s being produced by these storms.”
According to the National Weather Service, Sunday’s storm brought 1.68 inches of rain along the S-turns in Big Cottonwood Canyon, 1.52 inches of rain to the University of Utah, 1.5 inches to Bountiful, 1.13 inches to Tooele, and lesser amounts elsewhere in northern Utah.
In recent weeks, the Great Salt Lake surpassed the lowest water level ever recorded, and Lake Powell is on the verge of hitting its lowest level since the Glen Canyon Dam started trapping the Colorado River’s water in 1963.
“The Great Salt Lake’s not going to recover from these storms, and Lake Powell’s not going to recover,” Steenburgh said. “Most of the water to raise the level of those lakes is coming from snowpack runoff.”
The water level of the Great Salt Lake’s southern arm hit its lowest level in recorded history on July 24, with the daily average dipping below 4,191.3 feet above sea level — a record previously set in 1963.
In the week since, the lake’s level has averaged between 4,191.2 and 4,191.3 feet above sea level. On Monday morning, after Sunday night’s downpour across northern Utah, the lake’s water level spiked to 4,192.2 feet above sea level at 7:15 a.m., then settled back down to around 4,191.2 feet.
The water elevation at Lake Powell is expected to drop below 3,555.1 feet above sea level — the record set in 2005 — according to a U.S. Bureau of Reclamation report on July 22.
On Sunday, the lake’s level was at 3,554 feet above sea level, according to a Bureau of Reclamation website.
After a long drought, a big storm presents its own problems in urban areas, Steenburgh said. Dry soil may be resistant to the first drops of rain, so some water will run off before it starts soaking in. Also, if an area has gone without rain for a long time, debris may pile up in gutters — so when the rain does hit, blockages may happen, he said.
There are upsides to a summer storm, though.
A good rainstorm can improve and increase soil moisture, said Candice Hasenyager, deputy director of the Utah Division of Water Resources. When the soil carries enough moisture in the fall, she said, it freezes in the winter, and then thaws in the spring — and that moisture then makes spring runoff more efficient.
A rainstorm also improves streamflow, Hasenyager said, and reduce the sediment that can build up in dry weather.
Also, Hasenyager and Steenburgh agreed, that a good rain reduces demand for water use. Many homeowners can turn off their sprinklers for a week, they said, because lawns probably soaked up enough rainwater to go without the added watering.